A G U I D E F O R L A B O R AT O R I E S Pure labwater guide An essential overview of lab water purification applications, monitoring and standards. Dedicated to Discovery 2 Dedicated to Discovery PURE LABWATER GUIDE Inside 3-5 Introduction 6-16 Research and analysis applications 17-20 Clinical diagnostics 21-23 Healthcare 23-47 Water purification overview 48 Glossary 51 Further reading 3 Dedicated to Discovery PURE LABWATER GUIDE The pure labwater guide Introduction The Pure LabWater Guide is an essential resource for individuals who use pure water or wish to learn more about the subject. Providing an overview of water purification requirements, techniques and applications in science and medicine, this educational guide will enable you to choose the correct grade of water and most reliable method of production at an economical cost to both your budget and the environment. C H A L L E N G E S : vary significantly in purity both from There are 5 classes of impurities found I M P U R I T I E S A N D one geographical region to another in natural and drinking water: and from season to season. VA R I AT I O N S I N • Suspended particles D R I N K I N G WAT E R In today’s laboratories, the availability • Dissolved inorganic compounds of pure water is essential, and Water for most laboratory and clinical while domestic consumers consider • Dissolved organic compounds applications is usually purified from tap water to be “pure”, laboratory drinking water. However, the unique scientists and healthcare professionals • Microorganisms & biomolecules ability of water to dissolve (to some regard it as highly contaminated. • Dissolved gases extent) virtually every chemical Analytical and experimental scientists The overall objective of water compound and support practically are concerned with elements and purification methods for scientific every form of life means that compounds at concentrations in the and medical applications is to remove drinking water supplies contain many parts per billion (ppb) range or lower drinking water impurities while substances in solution or suspension; as many of these contaminants can minimising additional contamination additional impurities are derived have a negative effect on applications from purification system components during the drinking water purification through their interaction with other and bacterial growth. process. Furthermore, unlike other substances, including the substance raw materials, drinking water may under analysis. 4 Dedicated to Discovery PURE LABWATER GUIDE “Pure water is the most common substance that underpins a vast number of diverse scientific and medical applications – its importance should never be undervalued.” H O W T O U S E S E C T I O N 1 T H I S G U I D E R E S E A R C H A N D T E S T I N G Focuses on the vast range of applications that are performed in different laboratories, spanning basic glassware washing and rinsing through to the most critical molecular biology and cell culture techniques. It outlines the This guide is written by ELGA and types of purified water required for each category of application. is based on more than 70 years’ experience dedicated solely to the S E C T I O N 2 research, design, manufacture and C L I N I C A L D I A G N O S T I C S installation of water purification systems. The comprehensive Pure Highlights the importance of using extremely pure water to obtain valid LabWater Guide is an amalgamation and reliable chemical test results. It outlines the international standards of our original Pure LabWater and regulations required for these applications. Guide and Pure Clinical LabWater S E C T I O N 3 Guide, first published in 1991 and H E A LT H C A R E 2003 respectively. In addition to providing updates in the field of We outline numerous applications in Healthcare that require high-purity water purification (i.e. new water water, including the decontamination cleaning process for rinsing surgical purification technologies, additional instruments (e.g. endoscopes) and the production of steam for instrument applications and revised standards) sterilisation. It details the stringent guidelines and purified water standards the guide has been designed so that that are now being imposed for these applications. the information you require can be more easily accessed. Throughout S E C T I O N 4 this guide you will see hints and WAT E R P U R I F I C AT I O N O V E R V I E W tips and “Pure Facts” about water Provides a comprehensive overview about pure water, detailing the types purification with diagrams that of impurities found in water and the technologies, system design and summarise important technologies, components that are required to successfully remove them. The selection of systems and processes. A glossary the initial stages of a purification system will depend on the characteristics is provided at the back so that you of the feedwater and the entire process starts with a pretreatment stage. can simultaneously refer to and The major water purification technologies are outlined and each has its understand technical terms you advantages and restrictions; for example, some technologies can remove are less familiar with. large amounts of several impurities, while others can remove one specific This guide is divided into type of impurity down to extremely low levels. 4 easy-to-access sections. There are a myriad of different published standards that define the water • Research and testing (section 1) quality required for specific applications. ASTM. (American Society for Testing • Clinical diagnostics (section 2) and Materials) and ISO. (International Organization for Standardization) 3696 • Healthcare (section 3) provide guidelines for laboratory applications; CLSI. (Clinical and Laboratory • Water purification overview Standards Institute) guidelines define water quality requirements for clinical (section 4, further divided into 5 laboratories. Some laboratories will also adopt standards outlined in the subsections) European, US or Japanese Pharmacopoeia. However, very few of these • Production of drinking water standards are specific to your particular application; going too far will result • Impurities in drinking water in unnecessary costs or not far enough will endanger the accuracy of your • Water purification technologies results. This guide will allow you to navigate through the maze of standards • Maintaining the purity of and help you to choose with ease the right type of purified water and purified water method of production to provide you with the correct purity at an economical • Purified water standards cost to your budget and the environment. 5 Dedicated to Discovery PURE LABWATER GUIDE A B O U T E L G A P U R E FAC T S – WAT E R D E FI N ITIO N S As an integral part of Veolia, the world’s Numerous water quality by companies based on physical leading water service company, ELGA standards exist worldwide and chemical limits. There is provides a reliable source of water defined in laws and regulations, often some confusion about that economically meets the required in addition to generic water quality definitions, compliancy of all our customers’ classifications of water adopted so let’s revisit some basics: scientific and medical applications. With more than 70 years’ experience • Purified water is a general term meaning that water has been dedicated solely to pioneering water mechanically filtered or processed to remove impurities. purification systems, we are continuing • Demineralized water refers to water that has undergone a to apply cutting-edge process to remove minerals and salts from it. Unlike distillation, research with innovative and demineralization does not remove bacteria or viruses. ergonomic design. ELGA delivers robust • Deionized water (DI water, DIW or de-ionized water), often and easy-to-install systems to meet synonymous with demineralized water / DM water, has almost our customers ever changing needs. all of its mineral ions such as sodium, calcium, iron, copper, We also work very closely with leading chloride and sulfate removed. Deionization is a chemical process laboratory instrument companies to that uses ion-exchange resins to exchange hydrogen and customize water purification systems hydroxide ions for dissolved minerals and then recombine to for specific applications. Additionally, form water. Most non-particulate water impurities are dissolved we play a pro-active role with the salts, so deionization produces highly pure water that is generally water standards organisations which similar to distilled water. develop and recommend the Lab water quality requirements. • Distilled water has been boiled into vapor and condensed back With a network of over 600 service into liquid in a separate container. Impurities with a higher boiling point than that of water remain in the original container. centres worldwide, ELGA guarantees Double-distilled water (abbreviated “ddH2O”, “Bidest. water” an unrivalled package of service and or “DDW”) is prepared by slow boiling the uncontaminated support, no matter where you are, condensed water vapor from a prior slow boiling for its entire range of water purification systems. 1 9 3 7 1 9 6 0 1 9 8 0 - 1 9 5 5 - 1 9 7 0 - 1 9 8 9 1 9 9 0 - 1 9 9 9 2 0 0 0 2 0 0 3 2 0 0 4 Walter Lorch ELGA ELGA established ELGA launched the PURELAB UHQ, ELGA became ELGA ELGA launched founded ELGA. collaborated the School of Water a combination of ion exchange, the Laboratory launched the BIOPURE the Distillation was with London Sciences. Walter membrane processes, adsorption Water division revolutionary first product at the forefront School of Lorch published and photo-oxidation in a water of Veolia. ELGA CENTRA specifically of water Pharmacy ‘The Handbook of purification ‘system’ that provides launched the systems, the designed to purification, to develop Water Purification’. high-purity water at minimum costs. Option-E5, the first packaged meet the latest however the products aimed ELGA was the first ELGA wins the Queens award for first laboratory centralised stringent limitations of this at the hospital to introduce UV design. ELGA invented the ‘Type II’ purification system for water technology, with market, photo-oxidation or distillation replacement system, system to feature laboratory standards regards purity, laboratories to a laboratory which became incorporated into recirculating water in medical provided a driver and general purification their ‘Option’ range of products. Electro purification applications for change. The industry system. ELGA ELGA developed MEDICA, the Deionisation of cartridge-type launched MedRo, a first water purification systems treated water deioniser was system specifically specifically designed for the clinical invented by designed for the diagnostic market. ELGA launch the Walter Lorch renal market PureSure system (using multistage monitoring) as well as our real-time method of TOC monitoring 6 Dedicated to Discovery PURE LABWATER GUIDE Section 1 Research and analysis applications Scientists perform a vast range of applications in many different kinds of laboratories. Water has a set of unique properties as a solvent (such as a high dielectric constant and good solubility for minerals) and is therefore often used in analytical applications. Therefore, different grades of water must be purified and utilised to match the required procedures or appliances. Water is one of the major components in many applications, but the significance of its purity is often not recognised. 7 Dedicated to Discovery PURE LABWATER GUIDE A B O U T T H I S S E C T I O N In this section we highlight some There are many water quality defined by measurable physical and common applications and provide standards published throughout the chemical limits. Throughout this guide guidance on the water quality world, however only a few are relevant we will refer to the “Types” of purified required. We also provide some to specific research applications. This water referred to in this chart (see guidance on what purification has resulted in the majority of water below). technologies you should be looking purification companies, including ELGA, for in your water purification system. adopting broad generic classifications Grade of water Resistivity MΩ-cm TOC (PPB) Bacteria Endotoxin (EU/mL) Type I+ 18.2 <5 <1 <0.03 Type I >18 <10 <1 <0.03 Type II+ >10 <50 <10 n/a Type II >1 <50 <100 n/a Type III >0.05 <200 <1000 n/a Table 1: Details of various water grades and typical applications. TOC, total organic carbon; ppb, parts per billion; CFU, colony forming units; EU, endotoxin units. T Y P E I + T Y P E I T Y P E I I + T Y P E I I T Y P E I I I Goes beyond Often referred to as ultra pure, this grade is the grade for The grade for The grade the purity is required for some of the most water- general laboratory general laboratory recommended for requirements of critical applications such as HPLC (High applications applications. This non-critical work Type 1 water’ Performance Liquid Chromatography) requiring higher may include media which may include mobile phase preparation, as well as inorganic purity. preparation, pH glassware rinsing, blanks and sample dilution for other key solutions and water baths, autoclave analytical techniques; such as GC (Gas buffers and for and disinfector feed as Chromatography), AAS (Atomic Absorption certain clinical well as environmental Spectrophotometry) and ICP-MS (Inductively analysers. It is also chambers and plant Coupled Plasma Mass Spectrometry). Type I is common for Type II growth rooms. These also required for molecular and microbiology systems to be used systems can also be applications as well as mammalian cell as a feed to a Type used to feed Type I culture and IVF (In Vitro Fertilisation). I system*. systems* *The production of ultra pure water (18.2 MΩ-cm resistivity, <5 ppb TOC) from tap water is usually carried out in two stages – pretreatment and polishing. Ideally, pretreatment reduces all the major types of impurities – inorganic, organic, microbiological and particulate – by over 95%. This can be most effectively achieved using reverse osmosis or reverse osmosis combined with ion exchange or EDI. Alternatively ion exchange can be used but this cannot reduce the levels of organic, bacterial and particulate impurities to the same extent. The better the pretreatment the higher potential quality of the final ultra pure water. 8 Dedicated to Discovery PURE LABWATER GUIDE Analytical and general applications of purified water Summarised on P13 E L E C T R O - indicator electrode and a reference another. In these experiments the C H E M I S T R Y electrode (distinct from the reference total current passed is measured electrode used in the three electrode directly or indirectly to determine Since these techniques rely on the system). Only demineralised water the number of electrons passed. This sensitive measurement of tiny is used with electrodes since can indicate the concentration of the electrical signals, it is vital that mineralic water contaminats will analyte or, when the concentration the water used produces minimal interfere with the electric potential is known, the number of electrons interference due to background of the electrodes. Potentiometry is involved with a redox couple. Bulk contamination. ASMT Type II water, usually conducted in an ion selective electrolysis, also known as controlled typically with a TOC (Total Organic way with a different electrode potential coulometry, or some hybrid Carbon) <50 ppb and a bacterial count for each ion. The most common of the two names, is perhaps the most below 1 CFU/ml (Colony Forming Units per millilitre) is recommended potentiometric electrode is the glass common form of coulometry. pH electrode. for electrochemistry applications. For Voltammetry ultra trace electrochemical analyses pH measurement Voltammetry applies a constant and/ Type I (ultra pure) water is required. pH is a subclass of potentiometry or varying potential at an electrode’s TECHNIQUES INCLUDE and is used to measure the acidity or surface and measures the resulting alkalinity of a liquid. Measurement current with a three electrode Potentiometry Potentiometry measures the potential of pH in pure water is problematic system. This method can reveal the of a solution between two electrodes. due to the low ionic strength of reduction potential of an analyte and This is a passive technique, affecting the solution and because the rapid electrochemical reactivity among the solution very little in the process. uptake of carbon dioxide affects the other things. This method in practical The potential is then related to observed reading. terms is nondestructive since only a the concentration of one or more Coulometry very, small amount of the analyte is analytes. The cell structure used is Coulometry uses applied current or consumed at the two-dimensional often referred to as an electrode even potential to completely convert an surface of the working and though it contains two electrodes: an analyte from one oxidation state to auxiliary electrode. 9 Dedicated to Discovery PURE LABWATER GUIDE Polarography Amperometry distinguishes amperometry from Polarography is a subclass of Amperometry is a subclass other forms of voltammetry is that voltammetry that employs a of voltammetry in which the it is common to sum the currents dropping mercury electrode as the electrode is held at constant over a given time period rather working electrode and often uses potentials for various lengths than considering them at individual the resulting mercury pool as the of time. This is mostly a historic potentials. This summing can result auxiliary electrode. Concern over distinction that still results in in larger data sets and reduced the toxicity of mercury, combined some confusion, for example, error. Amperometric titration is a with the development of affordable, differential pulse voltammetry technique that would be considered inert, easily cleaned, high quality is also referred to as differential amperometry since it measures the electrodes made of materials such as pulse amperometry, which can current, but would not be considered noble metals and glass carbon, has be seen as the combination of voltammetry since the entire solution caused a great reduction in the use of linear sweep voltammetry and is transformed during mercury electrodes. chronoamperometry. One thing that the experiment. I D E N T I F Y I N G Y O U R D R I N K I N G WAT E R Q U A L I T Y Over 70 years of experience in the lab water industry, combined with Veolia’s expertise in running many municipal treatment plants, gives ELGA unsurpassed knowledge about feedwater qualities throughout the world. On our first visit to your laboratory we will carry out a test, on site, to analyse your feed water quality. Armed with data about your laboratory’s water quality, required applications, lab design and budget, our sales team will deliver an informed proposal about the best water purification solutions to suit your needs. S P E C T R O S C O P Y measurement of a quantity as a variable. A plot of the response as a function of either wavelength or function of wavelength — or more & S P E C T R O M E T R Y frequency. Thus it also can refer to commonly frequency — is referred to Spectroscopy was historically the interactions with particle radiation as a spectrum. study of the interaction between or a response to an alternating field Spectrometry is the spectroscopic radiation and matter as a function or varying frequency (v). Once the technique that is employed to assess of wavelength (l), and it referred very close relationship between the concentration or amount of a to the use of visible light dispersed photon energy and frequency (E=hv) given substances and the instrument according to its wavelength, i.e. was realised, where h is the Plank that performs such measurements is by a prism. Later the concept was constant, a further extension of a spectrometer or spectrograph. further expanded to comprise any the definition added energy (E) as a 10 Dedicated to Discovery PURE LABWATER GUIDE TECHNIQUES INCLUDE Flame Atomic Absorption Spectrophotometry (F-AAS) Although somewhat eclipsed by ICP-MS and ICP-ES for multielement analyses, the relatively modest cost of AAS ensures its use in smaller laboratories or for specific analyses. Depending on the element, detection limits vary from low ppb to ppm levels. ASTM Type II water is usually pure enough for most routine AAS and there is no requirement for low levels of organic compounds or bacteria. Gas Chromatography – Mass Spectrometry (GC-MS) For GC, purified water is used to prepare blanks, standards and sample pretreatments, e.g. solid phase extraction. Since high sensitivity can be achieved in GC- MS, the requirement for water The PureSure System purity is extremely stringent. Very At ELGA LabWater we fi t an extra sensor between low TOC levels, i.e. less than 3 ppb, the two purifi cation stages of an ultra pure are required and this can best be system. This ensures that the second purifi cation pack can be changed before weakly charged achieved by using a top-of-the-range impurities contaminate your application. polisher that is fed with water that has been pre-treated by Reverse Osmosis for removal of ions and organic compounds. Graphite Furnace Atomic Absorption permits trace analysis of complex metals, semi-metals, phosphorous Spectrophotometry (GFAAS) also mixtures and therefore requires and Sulphur have detection limits known as Carbon Furnace Atomic high purity water. All sample in the ppb (μg/l) range and requires Absorption Spectrophotometry (CFAAS) pretreatments such as solid phase fairly stringent water purity. A high This variant of AAS in which the flame extraction and sample preparation purity Type I water system (polisher), is replaced with an electrically heated steps require ASTM Type I (ultra is preferred, giving >18 MΩ-cm graphite tube or rod can achieve very pure) water, which is produced by resistivity, however TOC requirements high sensitivity in elemental analysis. a top of the range water ‘polisher’ are generally not critical and pre- A top of the range ASTM Type I water system. This gives ppt levels of treatment can be by reverse osmosis polisher is required that ensures ppt elemental impurities, 18.2 MΩ-cm or ion exchange. levels of elemental impurities, 18.2 resistivity water and an extremely Inductively Coupled Plasma Mass MΩ-cm resistivity ultra pure and low low TOC, typically <3 ppb. Multi-stage Spectrometry (ICP-MS) total organic content (TOC), while monitoring (see above) is the only Advances in modern analytical multi-stage monitoring (as delivered method that guarantees this level of instrumentation have continued to by the ELGA PureSure system – see purity and the ultimate performance improve the sensitivity of trace metal above) provides the best guarantee is achieved with enhanced analysis. These elements are now of purity. Ultimate performance pretreatment followed by continuous measured at ppt and sub-ppt levels is achieved when enhanced pre- recirculation and repurification of the using techniques such as ICP-MS. treatment is followed by continuous polished water. Trace analytical work requires water recirculation and repurification of Inductively Coupled Plasma Atomic that is free from the components to the purified water. Emission Spectrometry (ICP-AES) be measured and demands the same Mass spectrometry In ICP-AES, sensitivity differs markedly extremely stringent water purity This highly sensitive technique for different elements, however for the most sensitive ICP-MS work. 11 Dedicated to Discovery PURE LABWATER GUIDE Typically cleanroom facilities are with enhanced pre-treatment from a (<50 ppb) is of particular importance preferred for preparing high-quality recirculating ASTM Type II system. in techniques where UV detection reagents for blank analysis, standard systems are used, as dissolved Spectrophotometry dilutions and sample preparations. organics may interfere with detection. The water purifying system specified Purified water for spectrophotometric should be a purpose-designed ASTM applications is recommended to be Type I system. This should include at least of Type II quality with a low a form of multi-stage monitoring level of inorganic, organic or colloidal (see PureSure Diagram, page 10) contaminants. Typically, the water to guarantee these levels of purity. has a resistivity >1 MΩ-cm and has Ultimate performance is achieved been micro-filtered. Low TOC content CHROMATOGRAPHY sample pretreatment require extreme- can be analyzed in this way. A top of ly stringent, high quality pure water the range Type I (preferably Type I+) Chromatography may be (HPLC grade water), where the lowest water system is essential for obtaining preparative or analytical, but the possible TOC levels are typically less ppt levels of elemental impurities, 18.2 two are not mutually exclusive. than 3 ppb (see graph). This can be best MΩ-cm resistivity ultra pure and low Preparative chromatography seeks achieved with a top-of the-range Type TOC. Multi-stage monitoring provides to separate the components of a I water system (polisher) especially a guarantee of purity not offered by mixture for further use. Analytical designed for the purpose, fed with Type alternatives (see PureSure diagram, chromatography normally operates II or Type III water pre-treated by RO page 10). The ultimate performance is with smaller amounts of material (reverse osmosis). achieved with enhanced pre-treatment and seeks to measure the relative followed by continuous recirculation proportions of analytes in a mixture. Ion Chromatography (IC) and repurification of Type I water. IC determines minor and major High Performance Liquid components in a range of substances Chromatography (HPLC) down to 0.1 ppm by direct injection Trace gradient HPLC of primary HPLC can be used for the direct analysis of 10 to 50 microlitre samples. Highly grade and ultra pure water and determination of minor and major purified water is needed for blanks, components in a complex mixture. In standards and to prepare eluents. the mobile phase, purified water of While ASTM Type I water is preferred, general laboratory grade (ASTM Type II) Type II+ water is often adequate, espe- with a TOC of typically <50 ppb and a cially if price is an issue. Extremely low resistivity >1 MΩ-cm is used to pre- limits of detection (down to low ppt RO permeate pare blanks, standards and for sample levels) can be achieved using IC if the pre-treatment. Ultra-pure water ions are preconcentrated on a short Gradient HPLC is capable of extremely ion exchange column and then eluted low detection limits, e.g. well below 1 into the eluent stream for separation U A m Blank ppb, therefore blanks, standards and and analysis. 50 or 100 ml of sample Time 12 Dedicated to Discovery PURE LABWATER GUIDE G E N E R A L standards must be of sufficient specifications for the water used L A B O R AT O R Y purity that subsequent analyses to produce ‘pure steam’ for used in A P P L I C AT I O N S are not affected. Preparing general- disinfection services in healthcare purpose buffers, blanks and environments. General chemistry standards for general chemistry Total Organic Carbon (TOC) analysis Laboratory grade purified water with techniques, and for analyses > 1 This non-specific method is capable resistivity >1 MΩ-cm, TOC less than ppm the use of a general laboratory of quantifying the overall carbon 50 ppb and bacterial count of <10 grade purified water with a typical content of materials. Applications CFU/ml is recommended for general resistivity of >1 MΩ-cm, a TOC of <50 range from high levels in effluents chemistry applications. ppb and low bacteria will enable and process streams to sub-ppb Glassware washing/ rinsing accurate results. For trace analysis levels in ultra pure water. Samples Glassware washing is a routine practice at ppb levels or lower, ASTM Type are diluted and reagents and in most laboratories and the grade I (ultra pure) water is required for standards prepared with water. of water required depends on the preparing blanks and standards. For high level measurement Type II nature of the applications. To minimize SPE – Solid Phase Extraction water is adequate, while trace work costs (and depending upon your local This technique is widely used in requires Type I (ultra pure) water. drinking water quality), most general trace organic determinations as a Water analysis purpose glassware can be washed with pretreatment to separate the trace Water analyses are required for a ASTM Type III water. For more sensitive components of interest from the wide range of different purposes, analytical or research techniques, major components of the matrix. e.g. ensuring that drinking water Type II water with a resistivity of 1 to For trace analysis water of the meets current standards, checking 15 MΩ-cm should be used. For critical highest organic purity is needed that purification processes have applications, such as trace analytical to prepare blanks and standards, been successful and environmental techniques (e.g. ICP-MS), cell culture and to rinse the solid phase. This testing of lakes and rivers. Water or stringent clinical methods (like can best be achieved with a top of analysis requires purified water DNA sequencing or extraction), the range Type I water system that for the preparation of samples, glassware should be washed with has a minimum TOC specification standards and blanks and it must ultra pure water, especially for the (especially designed for this be of sufficiently high purity that final rinse to ensure that the ultra purpose), and is fed with water it does not interfere with the pure buffers, media or diluents are pre-treated by reverse osmosis (RO). analytical techniques. These analysis contained in “noncontaminated” Additional operational protocols applications are usually performed glassware. For this, Type I (ultra pure) may be needed to ensure continual with ASTM Type II water with water, inorganics should be 18.2 high performance. resistivity of >5 MΩ-cm, TOC <50 ppb MΩ-cm, TOC < 10 ppb and bacterial and a bacterial count below 1 CFU/ml. counts <1 CFU/ml. Steam generators Steam generators are used in a Buffer and media preparation Qualitative analyses range of applications including clean The grade of pure water required to Most qualitative analysis methods for room humidification, moisturisation, prepare or dilute reagents depends major or minor constituents require direct steam heating, injection and on the sensitivity of the application. general laboratory grade purified in autoclaves and sterilisers. Most For many general chemistry water with resistivity >1 MΩ-cm, a steam generators benefit from applications sensitivity is not the TOC less than 50 ppb, low particulates pre-treatment of the water supply primary factor, and therefore Type and bacterial counts. However, for to avoid build-up, precipitation or II water is of sufficient purity. It has more sensitive techniques such as contamination in order to reduce the added advantage of having ICP-MS, ultra pure water from a top of maintenance, improve performance high purity in ionic terms and if the range water polisher is required and enhance hygiene levels. Steam UV and filtration technologies are to produce ppt levels of elemental generators can use ASTM Type III incorporated with recirculation, can impurities, 18.2 MΩ-cm resistivity quality water with conductivity in also ensure low levels of organic water and low TOC. the range of 1–50 μS/cm (0.02 to 1.0 contaminants and microorganisms. Sample dilution MΩ-cm resistivity), which is typically and reagent preparation produced by reverse osmosis The water required for diluting after suitable pre-treatment. samples, blanks, reagents and Some authorities now apply strict 13 Dedicated to Discovery PURE LABWATER GUIDE Environmental chambers “dusting” , i.e. silica deposits on plants concern, then the system should include and plant growth rooms or samples. In organisations that use full recirculation to the chamber as well The salt concentration and bacterial walk-in chambers, bacterial quality is as on-line UV recirculation for complete quality of the water are of major of growing concern as contamination sanitization of water. The ELGA range of concern. The removal of silica (present from airborne bacteria can threaten BIOPURE systems designed for stringent in some feed waters and not removed the results. A Type II or Type III water healthcare applications can be used by some purification techniques) is purification system is usually suitable, successfully in these situations. considered important in order to avoid however if the level of bacteria is a 14 Dedicated to Discovery PURE LABWATER GUIDE Life science applications Summarised on P16 R E S E A R C H methods, ultra centrifugation and that include dialysis, injectables and A P P L I C AT I O N S electrophoresis. The key requirement cell culture. Maximum permitted for water for electrophoresis is the levels range from 0.25 EU/ml Molecular biology absence of significant levels of (Endotoxin Units/millilitre) down to Water quality for microbiology biologically active molecules such 0.03 EU/ml. For endotoxin analysis must generally be high. Focusing on as endotoxins (typically <0.005 EU/ Type I (ultra pure) water is required the study of nucleic acids, proteins ml), nucleases and proteases (not with an appropriate endotoxin and enzymes, molecular biology detectable). This is best provided by specification of typically 0.05 EU/ml research can be seriously affected ultra pure water with a resistivity or less. Filtration with ultrafilters or by contaminating microorganisms of 18.2 MΩ-cm, TOC <10 ppb C, 0.1 charged filters, preferably combined and associated biologically active cell μm or lower particle filtration, and with UV photo-oxidation, will be debris and products. Quite apart from bacterial counts below 1 CFU/ml. required. the use of nuclease-free water, care should be taken to ensure that an Electrophysiology Water for histology incorrect water purity does not have Electrophysiology methods vary Cells for histology are fixed and an effect on the salt concentrations of from measuring the biological non-viable therefore Type II water is prepared solutions for electrophoresis responses to electric currents and adequately pure. Typical values are a and blotting, as well as the production electromagnetic fields on whole resistivity of >1 MΩ-cm, TOC < 50 ppb of reagents for DNA sequencing, DNA animals to studies on single cells and <1 CFU/ml bacterial count. extraction and PCR (Polymerase Chain with microelectrodes and patch Hybridisation Reaction). The effect of humic acid as clamp techniques. These techniques – see Molecular biology a DNA inhibitor is often overlooked. are often very sensitive and can Hydroponics All of these concerns can be dealt yield inaccurate results if water that The water source for hydroponics with in choosing a purpose built, is relatively high in contaminating needs to be sufficiently pure to high quality “Genetics Grade” water inorganics is used. Typically, ASTM allow added concentrations of system which will provide water Type II water with a resistivity of >1 minerals and nutrients to be gauged above Type I purity. MΩ-cm, TOC <50 ppb and a bacterial accurately, as well as protecting count <1 CFU/ml should be employed. Electrophoresis against the possible indirect effects Macromolecules can be separated Endotoxin analysis that contamination could cause. For from one another by several different Endotoxin specifications are set for example, high levels of dissolved techniques, including chemical a wide variety of water applications elements, especially calcium and 15 Dedicated to Discovery PURE LABWATER GUIDE magnesium, can lead to high Monoclonal antibody research Mammalian and alkalinity that varies according to Monoclonal antibodies are a bacterial cell culture water depth. Sodium and chloride valuable tool in the development Successful cell culture requires highly can also cause direct toxicity to of new therapeutics and in-vivo pure media and buffers to ensure plants at high concentrations diagnostic products. Media or the cells are free from bacterial, as well as indirect damage by buffers of high purity are essential yeast and viral contaminants. interfering with the uptake of for the culture of sensitive cell lines While high levels of contaminating calcium, magnesium, nitrate and that express monoclonal antibodies. organics, inorganics and dissolved trace elements. Type II demineralised While high levels of contaminating gases can impact the culture water, with low levels of ionic, organics, inorganics and dissolved directly or indirectly, e.g. changes organic and bacterial contamination, gases can impact the culture in pH, the major concern for cell is recommended for hydroponics. directly or indirectly, e.g. changes culture applications is the effects in pH, the major concern for cell of contaminating microorganisms Immunocytochemistry The use of antibodies in culture applications is the effects of and their associated biologically contaminating microorganisms and active cell debris and products. Water immunocytochemistry for detecting used for bacterial cell culture is their associated biologically active the distribution of specific proteins cell debris and products. Water recommended to be of at least Type is prone to interferences from used for culturing bacteria that are II quality with resistivity >10 MΩ- contaminating microorganisms expressing monoclonal antibodies cm, a TOC of <50 ppb and a bacterial and associated biologically active should be of at least general count below 1 CFU/ml, while more cell debris and products, therefore sensitive mammalian cell culture laboratory grade, with resistivity >10 apyrogenic Type I (ultra pure) water MΩ-cm, a TOC of less than 50 ppb work requires apyrogenic, Type I is recommended. This is produced and a bacterial count below 1 CFU/ (ultra pure) water. by ‘polishing’ water that has been pre-purified by deionisation, reverse ml. For sensitive mammalian cell Radioimmunoassay (RIA) and osmosis or distillation and then culture, the use of apyrogenic, ASTM Enzyme-linked immunosorbent carrying out ultrafiltration to ensure Type I water is recommended. assay (ELISA) the removal of nucleases and Plant tissue culture The antibody reactions used in ELISA endotoxins. (micropropagation) are relatively robust and typically Micropropagation techniques allow do not require the highest purity Microbiological analysis large scale cloning of plant species water. Type II water with a resistivity Routine microbiological analysis >10 MΩ-cm, a TOC of <50 ppb and and the production of disease-free requires Type II purified water a bacterial count below 1 CFU/ml is plants. To minimise the effects which is largely free of bacterial suitable. contamination and has low levels of potentially contaminating biologically active species the use of of ionic, organic and particulate apyrogenic Type I (ultra pure) water impurities. Typical values are a is recommended. resistivity of >1 MΩ- cm, TOC <50 ppb and <1 CFU/ml bacterial count. PCR – see Molecular biology 16 Dedicated to Discovery PURE LABWATER GUIDE C L I N I C A L of purification technologies. While requires a detailed assessment of the H E A LT H C A R E the quality of water required for distribution and storage of water. It is A P P L I C AT I O N S clinical analysers is specified by the advisable to contact your local ELGA manufacturer, it typically would specialist for advice on this. Clinical biochemistry & immunology have a resistivity >10 MΩ-cm, TOC Endoscopy (See section 2 Clinical Diagnostics) <50 ppb and bacterial levels <5 CFU/ Critical applications in healthcare In clinical laboratories water should ml. However, with immunoassay can require very low (as little as 10 comply with appropriate water featuring increasingly in automated CFU/100ml) levels of bacteria. In quality standards; the most relevant analyser installations requirements some cases water with low endotoxin is the Clinical Laboratory Standards for higher bacterial qualities are levels is required for rinsing of Institute (CLSI) Type CLRW – see page increasing. This is largely because endoscopes after disinfection. ASTM 45. Care must be taken to ensure some assays utilize enzyme Type III or Type II grade water may water is completely sterile and usable markers which can be affected by be used with UV, ultrafiltration for sanitization procedures. Water by-products of bacteria present in and regular sanitisation. For critical used for feeding clinical analysers, water. A bacteria specification of <1 applications a purpose-built system or in any preparative or analytical CFU/ml (to the analyser rather than is recommended to achieve the levels procedure, should be of a high quality merely the outlet of the pure water of Biopurity needed (e.g. ELGA’s and is produced by a combination system) is needed in this case. This BIOPURE system). 17 Dedicated to Discovery PURE LABWATER GUIDE Section 2 Clinical diagnostics – specific impurities and their effects on tests Water quality is extremely important in clinical diagnostics. Water quality that is below the accepted standards not only affects the chemistry of the tests but can also affect the general operation of the analyser which, in turn, will reduce the reliability of the test results and increase calibration times and reagent costs. 18 Dedicated to Discovery PURE LABWATER GUIDE Diagrammatic view of how purified water is used in a clinical analyser F U N C T I O N S WAT E R Q U A L I T Y Purified water can be used for many different Poor water quality can affect the analyser functions in a clinical analyser, including: performance in many different ways, including: • Washing reaction cuvettes • Reduce the accuracy of pipetting volume due to • Feeding wash stations for probes particles and bacteria and stirrer paddles • Errors in photometric readings as a result of • Diluting reagents, samples and detergents particles interfering when a water bath is used • Incubator baths • Cuvette washing contamination, carryover and • An interface between syringe and sample water marks • Sample and reagent probe washing contamination and carryover • Affect sample and dilution leading to errors and poor reagent stability • As a zero standard (Ca, Mg, PO4, HCO3, etc.) Perhaps the most important aspect of pure water for calibration stability and sensitivity is reduced automated pathology analysers is reliability. • In immunoassay systems bacterial by-products Laboratories without the budget or space for a “duplex” (notably alkaline phosphatase) can interfere with system, require a robust design which incorporates some enzyme based assay results. ‘keep you going’ systems to be used the event of an emergency or systems failure. 19 Dedicated to Discovery PURE LABWATER GUIDE I N T E R N AT I O N A L S TA N D A R D S Since purified water is required Type I Type II Type Ill in all industries and sciencebased Bacteria (CFU/ml) max. 10 1000 NS organisations, this has led international and national standards pH NS NS 5.0-8.0 ° 10 1 0.1 authorities to establish water quality Resistivity (MO-cm @ 25 () min. standards for various applications. Si02 mg/I max. 0.05 0.1 1 The most relevant to the clinical Particulate matter 0.2 µm filter NS NS analyser market is the Clinical and Organic contaminants Activated carbon, NS NS Laboratory Standards Institute (CLSI) distillation or reverse formerly the National Committee for osmosis Clinical Laboratory Standards, (see Trace gradient HPLC of primary grade and ultra pure water Section 4: Purified Water Standards for further details). For cases where applications are sample identification, pre-analytics After validating the water as “fit for even more demanding than those (sample sorting, centrifugation, purpose”, it is critical to ensure that already established, ELGA works with de-capping, and allocation into it continues to meet the required the analyser company to specify the coded secondary tubes for various specifications; this is achieved by correct water grade. on-line and off-line work stations), measuring and documenting defined Clinical Laboratory Standards tracking systems for sample parameters at established regular Institute (CLSI) – Preparation and transfers to various users and finally intervals. Furthermore, this approach testing of reagent Water in the a refrigerated storage system for can detect deterioration of purification Clinical Laboratory – Third Edition sample retention enabling further components before this has impacted (1997) – Superseded in 2006 investigation and testing. on the required water quality. The key purified water guidelines Validation and trend monitoring Deterioration in a measured parameter, from CLSI 3rd edition were three Increasingly, validation of water e.g. changes in the required resistivity main types of water (Type I-III), of purification systems is becoming or TOC, indicates the need for system which Type I was most relevant to mandatory i.e. objective evidence maintenance or further investigation, to clinical laboratories and feeds to automated instruments. These have has to be provided that confirms ensure the required water specification a purification system meets the been replaced with the terms Clinical requirements for a specific use is always met. Additionally, recording Laboratory Reagent Water (CLRW), or application. Purified water critical parameters over a defined time Special Reagent Water (SRW) and should be validated as “fit for its is essential to identify gradual changes Intrument Feed Water. See page 45 intended purposes” and the purity in water quality and enable corrective for more details on these grades. specifications should be incorporated measures to be taken. For example, Trends in clinical chemistry into the water purification validation if ion exchange cartridges are used Greater efficiency, productivity and procedure. This is used to document beyond their intended life, impurities improved cost effectiveness are being the system’s ability to deliver which could interfere with the test achieved through automating clinical adequate volumes of purified water at analysis reactions can be eluted into the chemistry procedures. Automation can the stated specifications, as detailed in purified water at levels that may not now be incorporated into sophisticated the user requirement specification. register on built in monitoring systems. E F F E C T O F Higher purity process on an analyser, it is crucial Advancements in analyser that quality is monitored and verified P U R E WAT E R technologies demand good quality to ensure the integrity of test results. R E Q U I R E M E N T S water feed for maintaining high Integration of multiple technologies performance and reliability. Since into a single analyser to perform water is used in virtually every both chemistry and immunology 20 Dedicated to Discovery PURE LABWATER GUIDE applications results in higher quality However since they are more (CAP) is the accreditation body pure water being required for more susceptible to contaminant in the US, many laboratories in sensitive immunology testing. interference it is crucial that the water different countries also apply for is of the appropriate grade so that it CAP registration. CAP recommends While smaller sample and reagent will not contribute to this problem. that laboratory water should meet volumes reduce costs, they require the CLSI, Clinical Laboratory Reagent higher purity water because of the Regulatory Water (CLRW) grade standard increased sensitivity needed for In most countries public sector as a minimum. smaller sample volumes. laboratories are advised/regulated Tests by an accreditation body that Clinical analyser companies are establishes working standards also further regulated through The diagnosis or extent of certain diseases is associated with the and guidelines. While this is not organisations such as the Federal mandatory for private sector Drug Association (FDA) and Medical levels of specific proteins, known laboratories the significant Devices Agency. Ultimately the as biomarkers, in the blood – for credibility and advantages gained analyser companies are responsible example, elevated levels of Tropinin have resulted in more of these for ensuring their chemistries are signifies artherosclerosis, B-type laboratories registering with an validated and purified water of a natriuiretic peptide (BNP) indicates accreditation body, e.g. although the suitable standard is used so that all coronary artery disease, AFP indicates Collegiate of American Pathologists results are accurate and reproducible. hepatocellular carcinoma, CA-19-9 is correlated with pancreatic cancer and PSA is a marker for prostrate cancer. These proteins generally occur in very low concentrations e.g. nmols/l or pmols/l and are detected by techniques that are extremely sensitive. Compared to traditional tests/assays these current detection methods have the advantage of reducing the number of tests that have to be performed. 21 Dedicated to Discovery PURE LABWATER GUIDE Section 3 Healthcare Cleaning, sanitizing and and sterilising reusable medical equipment is becoming increasingly regulated by industry guidelines and international standards as concern grows over infection control in hospitals and the spread of MRSA, hepatitis, CJD and other resistant pathogens. There are two key elements – the protection of people (patients and staff) patient protection and the protection of equipment – to be considered in the sterilisation of reusable medical equipment: PAT I E N T brain function including memory during this incubation phase, neither P R O T E C T I O N changes, personality changes and they nor their healthcare providers ( AV O I D A N C E problems with movement, these will know that they are potentially (presently incurable) diseases are infectious, unless they belong to a O F C R O S S - ultimately fatal. The most common known at risk group. As the infectious C O N TA M I N AT I O N ) human prion diseases include, classic agent that causes the disease is Transmissible spongiform Creutzfeldt-Jakob Disease (CJD) and very stable and not inactivated by encephalopathies (TSEs), also known a new variant of Creutzfeld-Jakob methods routinely used to clean as prion diseases, are a group of Disease (vCJD), both related to bovine and sterilise instruments, there is a rare progressive conditions that spongiform encephalopathy (BSE). small risk that transmission could affect the brain and nervous system Typically, individuals do not exhibit take place during routine surgery on of humans and some mammals. symptoms of the disease for many such individuals, especially where Causing a gradual impairment of years following infection, therefore, this involves contact with high risk 22 Dedicated to Discovery PURE LABWATER GUIDE tissues such as brain or the central decontamination procedure used necessary to ensure that adherent nervous system. The fight against for medical instruments including infectious agents are removed these secondary, hospitalacquired endoscopes. together with the organic matter infections, also known as nosocomial To prevent prion contamination, that protects them, to enable better infections, and in particular, healthcare professionals must contact between the disinfectant the transmission of prionbased ensure that their instruments and and any remaining infectious agents on the surfaces of the instrument or illnesses has caused healthcare endoscopes are always perfectly clean, medical device. authorities and professional bodies disinfected and ready for use. The in some countries to regulate the thorough cleaning of instruments is P R O T E C T I N G before sterilisation/disinfection. • Rinsewater systems should be E Q U I P M E N T Additional economic benefits can regularly disinfected and validated be demonstrated where the use of to ensure they continue to meet the Inorganic contaminants such as improved water quality reduces the water specification rust, hard water deposits (scale) and volumes of chemical cleaners. • Water samples should be routinely residues from cleaners can, over time, damage the surface of the medical Typical water quality taken to demonstrate compliance instrument and create a habitat requirements include: These guidelines and standards that facilitates bacterial growth. • Bacteria Total Viable Count were introduced to minimise the Also heat and some disinfectants of less than 10 CFU/100ml risk of cross infection to patients (alcohols and aldehydes) are tissue from a range of bacteria including fixatives and may cause moving • Endotoxin levels of less than Mycobacteria, Pseudomonas and 0.25 EU/ml Staphylococcus epidermis. parts of a device to stiffen if the surfaces are not thoroughly cleaned • Conductivity of less than 30μS/cm D E C O N TA M - the equipment must be handled monitored within the limits specified I N AT I O N O F carefully to minimize any risk of by national regulations (for example E N D O S C O P E S recontamination. HTM0101 in the UK or perhaps United States Pharmacopeia ‘Water for Recently, the International Standards Most surgical instruments are Injection’ in some other countries). Organisation has published standards disinfected using a process of For many countries this requires an (ISO 15883 part 4) relating to the cleaning, thermal disinfection and endotoxin specification requirements and tests for washer sterilisation; however, endoscopes of <0.25 EU/ml. and several other instruments are disinfectors employing chemical disinfection for thermolabile To achieve these stringent standards thermally labile. Unable to tolerate endoscopes. These standards specify a water purification system that uses temperatures of 60oC or above, the use of water which has a microbial RO with recirculated UV and on-line they cannot, therefore, be thermally specification of <10 CFU/100ml (tested endotoxin filtration is recommended. disinfected and sterilised. on at least two samples) and if the However, overall the most important Instead, endoscopes are sterilized medical device comes into contact aspect of the requirements is the need using a chemical disinfection with the bloodstream or other to use a water purification system procedure and then rinsed in purified normally sterile areas of the body, that maintains biopurity through water to remove all traces of the then the standard requires that the simple and easy sanitisation. disinfectant. After decontamination, final rinse water is controlled and 23 Dedicated to Discovery PURE LABWATER GUIDE Section 4 Water purification overview T H E S O U R C E – Laboratory purified water is usually water is derived from upland sources, P R O D U C T I O N produced in situ from local drinking such as reservoirs, from rivers or O F D R I N K I N G water that has been produced by underground aquifers; drinking water treating natural water sources. The is produced by a series of steps that WAT E R overall requirement for producing vary with the water source, local and drinking water is that it conforms national regulations, and the to regulations and has acceptable choice of technologies. clarity, taste and odour. Natural 24 Dedicated to Discovery PURE LABWATER GUIDE Variations in raw water quality and hardness but a low organic content. are much less affected by the seasons. Unlike other raw materials, drinking River sources are intermediate in The quality and characteristics of the water may vary significantly in purity quality, but also often contain products drinking water supply determine the both from one geographical region to from industrial, agricultural and another and from season to season. domestic activities. Seasonal variations purification regime required to produce Water derived from an upland surface in water quality are most apparent in purified water. source, for instance, usually has surface waters. During the autumn a low content of dissolved salts and winter months, dead leaves and Natural water quality varies with: and is relatively soft, but has a decaying plants release large quantities • Geography of organic matter into streams, lakes high concentration of organic contamination, much of it colloidal. and reservoirs. As a result, organic • Source i.e. surface water, aquifer contamination in surface waters (underground source) By contrast, water from an underground reaches a peak in winter, and falls to a source generally has a high level of salts minimum in summer. Ground waters • Season D RI N KI N G WAT E R IS O F T E N • Passed through a series of screens to remove debris, and then mixed with ozone in contact tanks to oxidise pesticides and herbicides and kill bacteria and algae • Treated to destroy excess ozone • Clarified to remove suspended solids, which are collected as a sludge cake (sometimes a flocculent such as poly-aluminium chloride is added to help this process) • Sand gravity filtered and/or further ozonation • Granular activated carbon (GAC) filtered in order to trap solid and organic matter • Treated with chlorine to kill remaining bacteria. A small residual amount is left to maintain low bacterial levels. An extra ultrafiltration stage is also increasingly being used to remove Cryptosporidium. 25 Dedicated to Discovery PURE LABWATER GUIDE I M P U R I T I E S Dissolved inorganic compounds Dissolved organic compounds I N D R I N K I N G Inorganic substances are the major Organic impurities in water are mainly WAT E R impurities in water. They include: from biological origin. The decay of vegetal matter gives rise to byproducts The unique ability of water to • Calcium and magnesium salts, that include humic and fluvic acids, dissolve, to some extent, virtually which cause ‘temporary’ or tannins and lignin. Farming, paper every chemical compound and ‘permanent’ hardness making, domestic and industrial waste support practically every form of life • Carbon dioxide, which dissolves to also give rise to organic compounds means that drinking water supplies give weakly acidic carbonic acid including detergents, fats, oils, solvents contain many substances in solution • Sodium salts and residues from pesticides and or suspension. Many of these herbicides. In addition, water-borne contaminants can affect scientific • Silicates leached from sandy river beds organics may include compounds applications through their interaction • Ferrous and ferric iron compounds leached from pipework, tanks with other substances – some may derived from minerals and rusty and purification media. Dissolved be the substance you are analysing. iron pipes organics can interfere with analytical Suspended particles • Chlorides from saline intrusion techniques and affect biological Suspended matter in water includes • Aluminium from dosing experiments such as cell culture. Even hard particles (sand, rock, silt, pipework chemicals and minerals slight contamination present in water debris), soft particles (vegetal debris) • Phosphates from detergents used to prepare liquid chromatography and colloidal particles (organic or eluents can cause baseline instability, inorganic). Suspended particles can • Nitrates from fertilisers decrease sensitivity and resolution and foul reverse osmosis membranes, block Many other ions may be present also reduce the column lifetime. fine-bore analytical columns, as well as depending on the natural water source. Microorganisms interfere with the operation of valves Even at trace levels inorganic ions may Bacteria are the main microorganisms and meters. Colloidal particulates affect both organic and biochemical that contaminate natural water. give rise to haze or turbidity in the reactions by acting as a catalyst. Chlorination ensures the removal of water and thereby interfere with However, demineralised water may still harmful bacteria, but drinking water instrument operation. contain other contaminants. still contains live microorganisms, e.g. a typical bacterial level for a drinking laboratory water supply is ten colony forming units per millilitre (CFU/ml) or less. Bacteria are usually kept at low levels by employing residual levels of chlorine or other disinfectants; however, once these are removed during water purification, bacteria have the chance to proliferate. Bacteria can interfere with N AT U R A L A N D D RI N KI N G laboratory experiments either directly WAT E R CO N TAI N S FIV E M A JO R or through their by-products, such as C L A S S E S O F IM P U RITI E S: pyrogens, alkaline phosphatase or nucleases. Sanitization of water therefore plays an important role. • Suspended particles • Dissolved inorganic compounds • Dissolved organic compounds • Microorganisms • Dissolved gasses 26 Dedicated to Discovery PURE LABWATER GUIDE Dissolved gases bubble formation is a problem. Measuring impurities Drinking water is in equilibrium with Oxygen concentration can affect in drinking water the air and so contains dissolved gases specific biochemical reactions, and In order to design or select a water such as nitrogen, oxygen and carbon in applications where purified water purification system it is necessary to dioxide. In purified water carbon dioxide is used in open containers, it will have information on the feedwater dissociates to form a weak carbonic acid rapidly re-equilibrate with gases in composition, which is usually local the air. Both oxygen and nitrogen can drinking water. The average water (CO2 + H2O⇔H2CO3⇔ H+ + HCO3- ). form bubbles that are detrimental to quality data for your building can This weak anion reduces the capacity processes such as particle counting or be obtained from your local water of anion exchange resins. Dissolved spectrophotometer measures. supplier. Alternatively a sample can be oxygen is usually only an issue where taken and analysed. DI R E C T A N A LYSIS O F WAT E R • Filter-blocking potential is estimated using a fouling content by a total organic carbon (TOC) measurement. index (FI) test or, less reliably, turbidity. • Total viable bacterial counts or those of individual • Inorganic components can be determined by: species can be measured by incubation in a suitable – Ion chromatography growth medium. – ICP-mass spectrometry • Total dissolved solids (TDS) is the residue (in ppm) produced by evaporating a water sample to dryness – Spectrophotometric methods and heating at 180ºC. Since inorganic salts form the • Electrical conductivity provides a guide to potential greatest proportion of the TDS residue it is used as an problems. indicator of the total level of inorganic compounds. It • Organic compounds can be determined individually, e.g. can be measured directly or estimated by multiplying chromatographically, or an overall indication of organic the conductivity of the water, in μS/cm at 25ºC, by 0.7. 27 Dedicated to Discovery PURE LABWATER GUIDE Methods of water purification Water for most laboratory and clinical Bacteria – major water contaminants microbiological analysis of water can applications is usually purified Microorganisms and their by-products help to identify the problematic germs. from drinking water. The overall are a particular challenge as they The challenges for an ultra pure water objective is to remove drinking water enter unprotected water purification purification system are to: (i.e. feedwater) impurities while systems from the feedwater, any minimizing additional contamination openings in the system, or through • Remove the bacteria present in the from purification system components the point of use. They will grow as feedwater and bacterial growth. System design biofilms on all wet surfaces of the water • Ensure that minimal bacteria are and component selection are critical purification components, including present in the product water to success. The selection of the initial storage tanks and the plumbing of a stages of a purification system will distribution system. A biofilm is a layer • Prevent bacteria from entering the depend on the characteristics of composed mostly of glycoproteins system and re-contaminating it the feedwater. and heteropolysaccharides in which • Inhibit the growth of bacteria in The purification process starts with bacteria can multiply even when the the system by design and periodic concentration of nutrients in the water sanitization a pretreatment stage to reduce is very low, and the layer protects the damage of subsequent water organisms from periodic treatment purification components, ensure with biocides that are primarily effective reliable operation, and decrease in killing planktonic (free-floating) the operation cost by preventing microorganisms. excessively frequent replacement of expensive components. The major Sloughing biofilm and by-products water purification technologies of microorganism growth and are outlined below. Each has its metabolism (e.g. endotoxins) are always advantages and restrictions. potential contaminants of water. The 28 Dedicated to Discovery PURE LABWATER GUIDE O V E R V I E W Activated carbon (AC) – Activated carbon reacts chemically O F WAT E R in pre-treatment media with 2-4 times its weight of chlorine, P R E T R E AT M E N T Activated carbon is used in pretreating and very rapidly produces chlorides; feedwater. It removes chlorine and therefore even small carbon filters T E C H N O L O G I E S chloramine to prevent them from can effectively remove chlorine Microporous depth filters damaging membrane filters and from water. Microporous depth filters are matted ion exchange resins. Most activated In contrast, carbon breaks down fibers or materials compressed to carbon is produced by “activating” chloramines by a relatively slow form a matrix that provides a physical charcoal, from coconut shells or coal, catalytic reaction to produce barrier to the passage of particles by by roasting at 800-1000°C in the ammonia, nitrogen and chloride; random adsorption or entrapment, presence of water vapor and CO2. therefore, larger volumes of carbon and are characterised by nominal Acid washing removes most residual are needed for this process. Organic particle size ratings. Most raw waters oxides and other soluble material. fouling (the levels of which will contain colloids, which have a slight Activated carbon contains a maze of vary from site to site) can reduce negative charge (measured by the tiny pores with sizes that range from the effectiveness of carbon and this Zeta potential). Filter performance 500-1000 nm and a surface area of should be considered when choosing can be enhanced by using micro filters about 1000 square meters per gram. the size of carbon cylinders. that incorporate a modified surface, The adsorption process is controlled which will attract and retain these The large surface area and high by the diameter of the pores in the naturally occurring colloids, which are carbon filter and by the diffusion rate porosity of activated carbons, generally much smaller than the pore of organic molecules through the along with material they trap, sizes in the membrane. Depth filters pores. The rate of adsorption is make them a breeding place for (typically 1-50 μm) are commonly microorganisms; however, this can a function of molecular weight used as an economical way to remove and the molecular size of the partially be alleviated by the addition the bulk (> 98%) of suspended of insoluble biocides, such as silver, solids and to protect downstream organic components. to the carbon. Activated carbon beds purification technologies from fouling Carbon is used as either granules or need to be changed regularly to and clogging. They are replaced molded and encapsulated cartridges, minimize bacterial build-up. periodically. which produce fewer fine particles. P U R E FAC T S - P U R E FAC T S - M IC RO P O RO U S AC TIVAT E D D E P T H FI LT E R S CA R B O N Advantages: Advantages: • These prefilters provide an economical • These prefilters remove chlorine and way to remove >98% of suspended solids chloramine, and to some extent reduce thereby protecting processes downstream dissolved organic contamination from fouling and clogging • High capacity Restrictions: • Not effective in removing ions and particulates Restrictions: • Need to be changed regularly to minimize • Not regenerable bacterial build up • Can release carbon fines 29 Dedicated to Discovery PURE LABWATER GUIDE O V E R V I E W O F M A J O R WAT E R P U R I F I C AT I O N T E C H N O L O G I E S Microporous depth filters are matted Reverse osmosis (RO) RO membranes remove water contaminants that are less than 1 nm diameter and typically remove over 90% of ionic contamination, most organic contamination, and nearly all particulate contamination. RO removal of non-ionic contaminants with molecular weights <100 Dalton can be low. It increases at higher molecular weights and, in theory, molecules with molecular weights of >300 Daltons, passes through the membrane as feed and permeate divided by the feed including particles, colloids and permeate and the rest exits the conductivity, calculated as a %. microorganisms (also pyrogens), will be membrane as a concentrate that completely removed. Dissolved gases contains most of the salts, organics, “Ionic rejection” and “recovery” are not removed. vary with the feedwater, inlet and essentially all particulates. The pressure, water temperature and During the reverse osmosis of ratio of the volume of permeate to condition of the reverse osmosis water, feedwater is pumped past the volume of feedwater is referred to membrane. Reverse osmosis, with the input side of a RO membrane as the “recovery”. Operating a reverse under pressure (typically 4–15 bar, osmosis system with a low recovery its exceptional purifying efficiency, 60–220 psi) in cross-flow fashion. will reduce membrane fouling caused is a very cost-effective technology RO membranes are typically thin by precipitation of low solubility for the removal of the majority of film polyamide and are stable salts. However, recoveries of up to impurities. However, it is limited by over a wide pH range, but can be 75% are possible, depending on the the relatively slow rate of production damaged by oxidizing agents such as feedwater composition and filtration and is, therefore, normally used to chlorine. Pretreatment of feedwater and softening pretreatment. The fill a reservoir prior to use or further with microporous depth filters and performance of the reverse osmosis purification. A reverse osmosis water activated carbon is usually required component is typically monitored system protects the system from to protect the membrane from large by measuring the percent ionic colloids and organic fouling and is particulates, transition metals and free rejection, which is the difference often followed by ion exchange or chlorine. Typically 15-30% of feedwater between the conductivities of the electrodeionisation. P U R E FAC T S - R EV E R S E O S M O SIS Advantages: Restrictions: • Effective removal of all types of contaminants • Limited flow rates per surface unit require either a to varying degrees (bacteria, colloids, dissolved large membrane surface or temporary water storage inorganics, particles and pyrogens) • Require good pretreatment to avoid contaminants • Requires minimal maintenance damaging membrane: • Operation parameters – easy to monitor - Scaling: CaCO3 deposits on surface - Fouling: organic or colloid deposits on surface - Piercing: physical damage by particles 30 Dedicated to Discovery PURE LABWATER GUIDE Ion exchange (IX) ammonium hydroxide (Type 2) exhausted they are either returned to In this process beds of ion exchange derivatives of polysytrene crosslinked a regeneration station for recharging resins can efficiently remove ionized with divinylbenzene. or else discarded. Greater water purity species from water by exchanging and extended resin lifetimes can be Beds of ion exchange resins are them for H+ and OH- ions. These available as cartridges or cylinders achieved by pretreating the feedwater resins are sub 1 mm porous beads and are typically used for a period with reverse osmosis prior to ion made of highly cross-linked insoluble of time and then replaced, when exchange; this approach is often polymers with large numbers of cations and anions have replaced used for high purity laboratory water strongly ionic exchange sites. Ions most of the H+ and OH- active sites purifiers. This also avoids fouling of in solution migrate into the beads, in the resins. Cylinders can be fed the resin surface by large organic where, as a function of their relative directly with drinking water to provide molecules, which would charge densities (charge per hydrated purified water on demand. When reduce capacity. volume), they compete for the exchange sites. Deioinisation beads are either cationic or anionic and exchange either hydrogen ions for cations e.g. sodium, calcium and aluminium or hydroxyl ions for anions e.g. chloride, nitrate and sulfate. The hydrogen ion from the cation exchanger unites with the hydroxyl ion of the anion exchanger to form pure water. Strong cation resins are polysulfonic acid derivatives of polystyrene cross-linked with divinylbenzene. Strong anion resins are benzyltrimethyl quaternary ammonium hydroxide (Type 1) or benzyldimethlyethyl quaternary P U R E FAC T S - IO N E XC H A N G E Advantages: Restrictions: • Removes dissolved inorganic ions, • Does not effectively remove giving a resistivity of 18.2 MΩ- bacteria, organics, particles or cm (at 25OC); <1ppb total ionic pyrogens contamination • Finite capacity – once all ion sites • Regenerated by deionisation are occupied, ions are no longer using acid and bases or retained electrodeionisation • Chemically regenerated de-ionised • Relatively inexpensive beds can produce organics and particulates • Single use resins require good quality pre-treated water to be used efficiently and economically 31 Dedicated to Discovery PURE LABWATER GUIDE The very large surface areas of Resistivity monitoring is unlikely to first stage to detect bed exhaustion. ion exchange resins make them detect the initial release of these The second bed is then shifted to the a potential breeding place for weakly ionised species, including first position and a new bed installed microorganisms, and can lead to charged organics, silicates and in the second position. the release of fines and soluble borates. This situation is illustrated components. For these reasons, good in the graph above, which shows the This strategy makes efficient use of quality resins should be used, and bed release of silica, and organics as TOC the resin, because the first bed does volumes kept as small as reasonably before the resistivity falls detectably, not have to be exchanged until the possible. Filters are typically installed as an ion exchange bed begins intermediate resistivity drops below after the beds to trap fines and other to exhaust. 1 MΩ-cm @25°C, which is easily particulate matter. Bacterial build determined, and the second bed will up can be minimised by frequent The undetected release of weakly still retain virtually all of its initial recirculation of the water and by bound ionic contaminants can be capacity when it is moved to the regular cartridge replacement. As ion prevented by multi-stage monitoring primary position. Other, less effective, exchange beds exhaust, they release (e.g. ELGA’s PureSure), which uses pulses of contaminants that have two identical ion exchange resin beds approaches include replacing beds accumulated from the water. Strongly in series with a resistivity monitor well before they exhaust or the bound contaminants may displace between them. As the first (primary) use of specialised resins that bind weakly bound contaminants, so the bed begins to exhaust, the released weakly ionised species tighter. With first pulses of contaminants are likely weakly ionised species are bound by suitable choice of resin, pretreatment to be weakly ionised substances that the second (polishing) bed and thus and system design, ion exchange will have little effect on the resistivity are not present in the final product enables the lowest levels of ionic of the product water. water. Resistivity is measured after the contamination to be achieved. 32 Dedicated to Discovery PURE LABWATER GUIDE Electrodeionisation (EDI) Electrodeionisation is a technology that combines ion exchange resins and ion-selective membranes with direct current to remove ionised species from water. It’s development and use in water purification overcame some of the limitations of ion exchange resin beds, particularly the release of ions as the beds exhaust and the associated need to change or regenerate the resins. Water passes through one or more chambers filled with ion exchange resins held between cation or anion selective membranes. Ions that become bound to the ion exchange resins migrate to a separate chamber under the influence of beds typically are smaller and remain housed in wide cells that provide an externally applied electric field, in service for longer periods. The resins a flow path for the ions in transit, which also produces the H+ and OH- used in Electrodeionisation systems which offers advantages in the necessary to maintain the resins in can either be in separate chambers flexibility of design and mechanical their regenerated state. Ions in the of anion or cation beads, layers of simplicity at laboratory scale. The separate chamber are flushed to waste. each type within a single chamber resin in the cells provides a buffer The ion exchange beds in or an intimate mixture of cation and against changes in feedwater quality. Electrodeionisation systems are anion beads. ELGA’s laboratory EDI The quality of water produced is regenerated continuously, so they do process utilises separate beds of cation then further enhanced by passage not exhaust in the same way as ion and anion resins as well as a bed of through a mixed resin bed. Reverse exchange beds that are operated in intimately mixed resins. The separate osmosis is typically used before batch mode. Also, Electrodeionisation beds of cation and anion resins are Electrodeionisation to ensure that the Electrodeionisation “stack” is not overloaded with high levels of salts, organics or particles. The small volume of resins in the stack results in low P U R E FAC T S - IO N E XC H A N G E bleed of organic molecules. Typically, reverse osmosis removes about 95% of ions; Electrodeionisation will remove Advantages: Restrictions: about 95% of the remaining ions • Removes dissolved inorganic ions, • Removes only a restricted number as well as carbon dioxide and silica. giving a resistivity of 5 -17 MΩ-cm of charged organics therefore Typically, EDI product water has a (at 25OC) and a TOC content below cannot produce ultra pure water resistivity of 5 to 17 MΩ-cm (at 25°C) 20 ppb with a resistivity of 18.2 MΩ-cm and a TOC content below 20 ppb. • Environmentally friendly: • Feedwater must be of good quality Bacterial levels are minimised because so that it does not overload the EDI the chemical and electrical conditions – No chemical required for regenerating resin stack with organics, multi-valent within the system inhibit the growth salts or particles. It is typically of microorganisms. EDI will not – No chemical or resin disposal treated with RO normally provide ultra pure water with – Resins in the cells have a low a resistivity of 18.2 MΩ-cm; however, “bleed” of organics and buffer this can be efficiently achieved by against changes in feedwater incorporating a low volume of ion quality exchange resin down stream of the stack. This resin has very few ions to remove and will have a very long lifetime. 33 Dedicated to Discovery PURE LABWATER GUIDE Distillation Distillation is a long established method for water purification and separates water from contaminants by changing the state of water from a liquid phase to a gas phase and then back to a liquid phase. Each of these transitions provides an opportunity to separate water from contaminants. Water is first heated to boiling point and water vapour rises to a condenser where cooling water lowers the temperature so that the water vapour is condensed, collected and stored. In principle, distillation can remove all classes of water contaminants, with the exception of those that have vapour pressures close to water and azeotropes. Distillation is most effectively performed with pre-treated water to minimise the build up of precipitates and the carryover of impurities. Water produced by this method is called “distilled water”. Laboratory stills are unlikely to produce adequate purification from untreated feed water, especially if water. Careful design is essential stage of a still. Compound (multi- precipitation occurs, so laboratory to minimise the possible transfer stage) condensers that equilibrate stills are most frequently fed with of less volatile contaminants e.g. steam and boilinghot water in pre-purified water from RO or ion by splashing or by surface or steam multiple, specialized compartments exchange. Laboratory stills are entrainment. Contaminants that are necessary to remove these continuous; as boiler water is distilled have vapour pressures higher than contaminants efficiently. away, it is replaced with fresh feed water are removed in the condenser Contamination from the ambient air (e.g. dust, volatiles, etc.) must also be minimised. Like reverse osmosis, distillation only produces purified water slowly and the P U R E FAC T S - DISTI L L ATIO N distilled water must be stored for later use. Stills are very energy intensive – Advantages: • Should be fed with pre-purified typically using 1kW of electricity per water litre of water produced. Depending • Removes a wide range of on the design of the still, distilled contaminants • Distilled water can be prone to water can have a resistivity of around • Long shelf life re-contamination during 1 MΩ-cm as CO2 in the air dissolves in prolonged storage, therefore the distilled water. The distilled water requires meticulous maintenance Restrictions: will be sterile when freshly produced, • Slow at purifying water • Not economical or environmentally however to maintain sterility, it is friendly – requires large amounts collected in sterile storage bottles • Certain contaminants are of electrical energy for heating and then autoclaved; however, once transmitted at varying amounts and large volumes of tap the bottle is opened it is exposed to into the condensate water for cooling. bacteria and other airborne impurities and its purity rapidly deteriorates. 34 Dedicated to Discovery PURE LABWATER GUIDE Activated carbon – in Purified Water Microporous filters and periodic replacement) is The second major application of Microporous screen filters provide necessary to maintain desired levels activated carbon is in the removal a physical barrier to the passage of performance. Newly installed of organic compounds from purified of particles and microorganisms in filters usually require rinsing water, often in the purification loop purified water systems. Screen filters, before use to remove extractable prior to the final ion exchange bed. characterised by absolute particle contaminants. A microporous filter Activated carbon takes up water size ratings, have uniform molecular membrane is generally considered contaminants by virtue of ionic, polar structures, which, like a sieve, retain to be indispensable in a water and Van der Waals forces, and by all particles larger than the controlled purification system, unless it is surface-active attraction. Activated pore size on their surface. Screen replaced by an ultrafilter. carbon beds are prone to release filters (0.05 to 0.22 μm) are typically fines and soluble components into used as close as possible to the the water stream and do not remove point of use to trap microorganisms all dissolved organic contaminants, and fine particulates. Trapped but their use can produce a particulates, including significant reduction in TOC. A purer microorganisms or their metabolic form of activated carbon made from products, and soluble matter, can polymer beads is sometimes used for be leached from filters and suitable this application. maintenance (regular sanitisation P U R E FAC T S - P U R E FAC T S - AC TIVAT E D M IC RO P O RO U S CA R B O N FI LT E R S Advantages: Advantages: • Produce a significant • Screen filters function as reduction in TOC absolute filters that retain • Long life attributed to high and remove all particles and binding capacity microorganisms greater than their pore size Restrictions: • Operate efficiently unless damaged • Does not remove all dissolved • Easy maintenance, i.e. only organic contaminants need to be replaced • Sometimes releases fines and Restrictions: soluable components into the water stream • Become blocked when the surface is covered by contaminants, therefore should be used in last purification step as a guarantee • Does not remove dissolved inorganics, organics or pyrogens • Cannot be regenerated 35 Dedicated to Discovery PURE LABWATER GUIDE Ultrafilters (UF) UFs are membrane filters that remove particles as small as protein macromolecules. Pores are typically from 1 to 10 nm and membranes in the form of hollow fibres are often used to give higher flow rates. They are characterised by the efficiency with which they reduce the concentration of relevant contaminants to acceptable levels. UFs are usually installed near the outlet of a water purification system to reduce the concentration of microorganisms and large organic molecules, including nucleases and endotoxins. UFs must be regularly sanitised and/or replaced to maintain their effectiveness. UFs can be installed Vent filters Degassing (or De-aeration) in a traditional fashion, where all the Hydrophobic microporous filters membranes water flow is directed straight through are often fitted to water storage A contactor device uses a the membrane, or in “cross flow” containers as vent filters in order hydrophobic membrane filter to (tangential flow) fashion where a to prevent particulates, including remove gases (e.g. CO2, O2) from portion of the input water flows across bacteria, from entering the stored water. The water stream passes the membrane surface to reduce pure water. By combining absorptive on one side of the membrane and fouling by rinsing away contaminants. media with filter media, composite a flush gas or vacuum removes UF is an excellent technology for vent filters (CVF) can also minimise gases from the other side of the ensuring consistent ultra pure water CO2 and organic contamination of membrane. The removal rate of quality with respect to particles, stored water. Regular replacement is a species is dependent on the bacteria and pyrogens. essential to maintain effectiveness. permeability of the membrane, the contact area, contact time and the difference in partial pressure across the membrane. P U R E FAC T S - U LT R A FI LT E R S Advantages: • Effectively removes most colloids, enzymes, microorganisms particles and endotoxins above their rated sizes, keeping them above the ultrafilter surface • Efficient operation unless damaged • Lifetime can be extended by a regular high speed water flush Restrictions: • Does not remove dissolved inorganic or organic substances • Can block if presented with a high level of high molecular weight contaminants 36 Dedicated to Discovery PURE LABWATER GUIDE Ultraviolet (UV) light UV light is widely used as a bactericide and to break down and photo-oxidise organic contaminants to polar or ionized species for subsequent removal by ion exchange. The UV sources in laboratory water purification systems are low pressure mercury lamps that produce radiation with a wavelength of 254 nm. This has the greatest bactericidal action as it damages * * DNA and RNA polymerase at low doses thereby preventing replication, * * while higher doses are biocidal, thereby leading to sanitization and desinfection of water. UV chambers and lamps need to be designed to provide a sufficient dosage of UV to avoid production of live but inactivated microorganisms. Radiation at shorter wavelengths (185 nm) is most effective for oxidising organics as it breaks large organic molecules into smaller ionized components, which can then be removed by a downstream high purity ion exchange resin bed. Prior removal of organic ions, by initial ion exchange, optimises the effectiveness of this treatment. UV radiation at 185 nm is a highly effective oxidant and a key component in producing ultra pure water with the lowest levels of organic contaminants. P U R E FAC T S - U V LIG H T Advantages: Restrictions: • Oxidation of organic • Photo-oxidation of organics is compounds (185 nm and 254 a polishing step that can only nm) to reach TOC levels < 5 decrease the TOC levels by a ppb restricted amount • Effective bactericide treatment • No influence on ions, particles or colloids • The water’s resistivity is decreased as a result of the CO2 released by photo-oxidation, as it produces H2CO3 (H+, HCO3- ) 37 Dedicated to Discovery PURE LABWATER GUIDE System design particular application, it is necessary 90% of ions. The resultant primary Different water purification to use a combination of technologies. grade water, which is produced technologies have been described in relatively slowly and stored in a this section; each has its advantages Each system will require some pre- reservoir, will contain some level of and restrictions. Some are able to treatment based on the particular organic compounds, ions, bacteria and remove large fractions of several feedwater to remove particulates, cell debris, dissolved carbon dioxide impurities, while others are excellent chlorine or chloramine and, possibly, and oxygen. These stages can occur at removing one specific contaminant calcium and magnesium. This is in separate units either locally or in a down to extremely low levels. preferably followed by reverse larger system with a loop providing Therefore, in order to remove all osmosis to remove virtually all water to a single laboratory or an contaminants to produce the desired colloids, particles and high molecular entire building. level of water purification for a weight organic compounds and over The water is next treated by one or more techniques depending on the required purity – ion exchange and/or EDI to remove ions, activated carbon or other absorbents to remove organic compounds, UV light to kill bacteria and/or to oxidise residual organic compounds, microfiltration to remove particles and bacteria and ultrafiltration to remove endotoxins, proteases and nucleases. Any or all of these stages can be combined in the same unit as the reverse osmosis, or separately in a “polisher”. 38 Dedicated to Discovery PURE LABWATER GUIDE 39 Dedicated to Discovery PURE LABWATER GUIDE Storage and distribution are also critical and metals, other Reservoirs should be protected Storage and distribution are potential than stainless steel, should be from contaminants entering with sources of contamination, particularly avoided. There are many high purity suitable composite vent filters and from bacteria. Good design and plastics available but care needs to purified water is often recirculated proper maintenance regimes are be taken to avoid those with fillers continuously or, intermittently, needed to minimise these problems. and additives which could leach and through some of the purification The materials chosen for construction therefore contaminate the water. technologies to maintain purity. 40 Dedicated to Discovery PURE LABWATER GUIDE M O N I T O R I N G – associated electronics, frequently provided with temperature M A I N TA I N I N G T H E P U R I T Y compensation. The meter measures the resistance, R, O F P U R I F I E D WAT E R between the sensing electrodes of the conductivity cell. It is impractical to monitor all potential impurities in Conductivity values of less than purified water. Inorganic salts and dissolved organics are the major contaminants that affect most laboratory 2 μS/cm must be measured applications and, therefore, it is important that they are monitored on-line in laboratory water systems. The key on-line as high- rapid, on-line techniques are resistivity and TOC. purity water rapidly absorbs The conductivity, k, represents the total contributions of the contaminants from individual ions in the water and therefore provides valuable, the surroundings, non-specific indication of the ions in purified water. This particularly carbon includes all impurity ions and hydrogen and hydroxyl ions dioxide; causing its conductivity to rise. Although resistivity provides an excellent indication of the ionic quality of high purity water, it cannot indicate the presence or concentration of nonionised chemical species, nor is it sensitive to sub-ppb concentrations of ions due to equilibria with the hydrogen and hydroxyl ions from the water. When such levels are critical, individual contaminants may need to be measured using analytical techniques such as inductively coupled from the very slight natural dissociation of water. It is these plasma mass spectrometry, ion chromatography and hydrogen and hydroxyl ions that are responsible for totally graphite furnace AAS. pure water having a conductivity of 0.055 μS/cm at 25.C (a resistivity of 18.2 MΩ-cm). For a strongly ionised salt, the value of k is approximately proportional to the concentration of the salt in solution and to the mobilities of its ions which are expressed as u+ (cation) and u- (anion). The values of u+ and ualso depend strongly on the viscosity of the solution and, therefore, on the water temperature, t. For many ions, the relative temperature coefficient of u is around +2%/°C. In addition the value of the equilibrium constant for the dissociation of water, Kw, is also temperature dependent and so the conductivity of pure water, can rise by up to 6%/°C. Normal practice is to automatically correct all conductivity and resistivity values to 25.C. Resistivity and conductivity are easy and rapid to measure using an on-line conductivity cell (sensor) with cable and a meter, or display unit, with 41 Dedicated to Discovery PURE LABWATER GUIDE Total Organic Carbon (TOC) to detect organics The potential variety and complexity of organic compounds in purified water makes it impractical to measure them all routinely, therefore an indicator of overall organic contamination is used. The most practical has proved to be TOC, which oxidises organic substances in water samples and then measures the resultant oxidation products. A wide range of TOC analysers exist and can be broadly divided into those which Hints &Tips oxidise all the carbon to carbon dioxide Always run at least 5 litres of purified and measure the CO2 selectively and water to drain after a period of inactivity, those that either partially oxidise e.g. after the weekend, particularly when the organic compounds, to acids for using the water for critical applications. example, or fully oxidise all species present and measure the change in conductivity due to all the oxidized species. The former are usually used off-line to show compliance with TOC specifications, while the latter are used for on-line monitoring and will include, E L E C T RICA L for example, contributions of nitric and sulphuric acids from the oxidation of CO N D U C TIVIT Y/ N and S atoms. The main role of TOC is R E SISTIVIT Y TO for monitoring and trending. In most D E T E C T IO N S waters TOC cannot be related directly to the concentration of organic molecules as the amount of carbon is different in Electrical conductivity and resistivity are both different molecules. measures of a fluid’s ability to conduct electrical current. Conductivity is the reciprocal of resistivity, e.g. conductivity = 1/resistivity. The ionic content of purified water is provided by measuring electrolytic conductivity, k, and its reciprocal, resistivity, r. k=F.Σ ci zi ui r = 1/k Low conductivity = high resistivity In practice, conductivity units are typically used when referring to water ranging from raw water though to drinking water and primary grade, while resistivity units are used for ultra pure water such as deionised or reverse osmosis water. The unit of conductivity is the Siemen (S/cm) and the unit of resistivity is Ohms (Ω-cm). A Meg-ohm (MΩ-cm) =1,000,000 Ohms. Since conductivity and resistivity relate to an area between which current is measured i.e. length/ area, it is typical to see the units expressed as MΩ-cm or .S/cm. 42 Dedicated to Discovery PURE LABWATER GUIDE pH The measurement of pH is not recommended for pure water. High-purity water rapidly picks up contaminants that affect its pH and it also has a low conductance, which causes instability in most pH meters. Fortunately, since the concentration of hydrogen ions in the water affects both pH and resistivity, the pH must lie within certain limits for a given resistivity reading. For example, if the resistivity is 10 MΩ-cm, the pH must lie between 6.6 and 7.6 Monitoring biologically active species To monitor contaminating biologically differ considerably from those obtained components to ensure that the active species, samples of purified from plate counting as microorganisms product water meets specifications water are filtered through a sterile 0.22 growing in laboratory water purification at all times. Trend monitoring of μm membrane filter. Bacteria present systems do not necessarily grow quickly, parameters that measure product in the sample are trapped on the filter, or well, on plate media. Endotoxins water specifications makes it possible which is then placed on the surface of are lipopolysaccharides present in the to anticipate some maintenance. The a low nutrient media and incubated. cell walls of gram negative bacteria. frequency of maintenance activities The nutrients from the media diffuse They produce adverse effects in many should follow, as a minimum, the through the filter allowing the growth molecular biological procedures and a manufacturer’s recommendations. of colonies, which are counted, toxic response if injected into humans. Sanitisation of the water purification typically, after 3 to 5 days. Standard tests based on Limulus and distribution system is critical Since this “plate counting” technique Amebocyte Lysate activity are used to to ensure microbial contamination measure endotoxin levels. has an inherently long delay before is controlled within specifications. Similarly, other biologically active results can be obtained it is essential Sanitisation frequency must be species such as RNase, DNase and to use regular bacterial counts to adequate to maintain the purity proteases can severely interfere with monitor the background long-term specifications and is established many molecular biological techniques, bacterial acceptability. This is achieved use of nuclease free water is therefore based on system usage, regular using epifluorescence microscopy quality control trend data, and advised. Various specific tests, often of a stained, filtered sample and the system manufacturer’s in kit form, are available for detecting can be used to rapidly detect and recommendation. Chlorine solutions, these species off-line. distinguish between living and dead per-acetic acid and hydrogen microorganisms, making it useful when Procedures must be established for peroxide are often used as sanitants. a rapid corrective action is indicated. maintenance and/or replacement Epifluorescence counts are likely to of water purification system 43 Dedicated to Discovery PURE LABWATER GUIDE P U R I F I E D WAT E R conductivity of 1.0 to 0.1 μS/cm (a EDI and possibly with absorption and S TA N D A R D S resistivity of 1.0 to 10.0 MΩ-cm), UV treatment. and is produced by mixed-bed ion Standards define different laboratory exchange using strongly basic anion Ultra pure and water grades for both technical exchange resins. It may have a Ultra pure grade water approaches and economical reasons. The reason the theoretical levels of purity in relatively high and variable level of for these standards is to ensure that terms of resistivity, organic content, organic and bacterial contamination. the right water quality is used for a It is used for a variety of purposes, particle and bacteria counts. specific application, while minimizing including rinsing, making up general This level of purity is obtained by laboratory operating costs. In general, purpose analytical standards and ‘polishing’ water, which has been the purer the required grade of water, reagents and diluting samples. pre-purified by ion exchange, reverse osmosis or distillation. Typically, ultra the more expensive it is to produce. General laboratory pure water has a resistivity of 18.2 ELGA differentiates between four General laboratory grade water MΩ-cm, TOC <10 ppb C, 0.1 μm or general grades of purified laboratory not only has high purity in ionic finer particle filtration, and bacterial water: terms, but also low concentrations counts below 1 CFU/ml. Ultra pure Primary grade of organic compounds and grade water is required for a variety Primary grade water has the lowest microorganisms. A typical of sensitive analytical techniques level of purity, and normally has a specification would be a conductivity such as trace high performance of <1.0 μS/cm (resistivity >1.0 MΩ- liquid chromatography (HPLC), ion conductivity of 1-50 μS/cm. It can cm), a total organic carbon (TOC) chromatography (IC) and inductively be produced by weakly basic anion content of < 50 ppb and a bacterial coupled plasma spectrometry exchange resins, reverse osmosis or count below 1 CFU/ml. Water (ICPMS). Ultra pure apyrogenic single distillation. Weakly charged of this quality can be used for a water is required in applications anions, such as carbon dioxide and multiplicity of applications, ranging such as mammalian cell culture. silica may not be removed and, from the preparation of reagents Ultrafiltration is used to remove therefore, will be present in this and buffer solutions to nutrient any significant levels of biologically water grade. Typical applications media for bacterial cell culture and active species such as endotoxins for primary grade water include microbiological studies. Laboratory (typically <0.005 EU/ml), nucleases rinsing glassware, feeding washing grade water can be produced by and proteases (not detectable). machines and humidifiers. double distillation or by water Deionised purification systems incorporating Deionised water typically has a reverse osmosis and ion exchange or 44 Dedicated to Discovery PURE LABWATER GUIDE I N T E R N AT I O N A L they are not fully quoted and since procedure in which it is used. The S TA N D A R D S standards are regularly reviewed system producing purified water and updated, users should refer to must be validated to meet the Since purified water is required the latest version of the complete user requirement specification. in all industries and sciencebased standards. Regular monitoring trending and organisations, this has led documentation of appropriate international and national standards Clinical Laboratory Standards parameters must be carried out authorities to establish water quality Institute (CLSI) – Preparation to verify that water purification standards for various applications. and testing of reagent water in the technologies and systems are The most relevant to the clinical clinical laboratory – Third Edition working effectively. (1997) – Superseded in 2006 analyser market is the Clinical and Procedures must be established for Laboratory Standards Institute The key purified water guidelines system maintenance to keep the (CLSI) formerly the NCCLS (National from CLSI designated three main system in conformance with water Committee for Clinical Laboratory types of water (Type I-III), of which purity specifications. Standards). Type I is most relevant to clinical laboratories and feeds to automated Only one grade, Clinical Laboratory The relevant standards are: instruments. Reagent Water (CLRW) is defined in • Clinical and Laboratory Standards detail. It can be used to replace Type Clinical Laboratory Standards Institute (CLSI) – formerly NCCLS or Type II water from the former Institute (CLSI) – Preparation and guideline. The other grades, listed • The International Organization for testing of reagent water in the below are described in relation to Standardization (ISO) clinical laboratory – Fourth Edition their application and user defined (2006) • The American society for Testing and details: Material (ASTM) In order to encourage users to • Special reagent grade water (SRW) understand the important aspects • The Pharmacopoeia including USP, surrounding the choice of water • Instrument feed water EP and JP purification systems, the CLSI has • Water supplied for use as a diluent For cases where applications are even adopted a different approach in or reagent more demanding than those already the revised guideline. It has moved established, ELGA will work with the from Type I, II, III designations to an • Prepackaged bottle water company or organisation to specify emphasis on ensuring that the water • Autoclave and wash water the correct level and methods of is suitable for its use. applications purification. The product water meeting a set The standards in this section are specification must be validated as correct at going to press, however fit for purpose for each laboratory Type I Type II Type Ill Bacteria (CFU/ml) max. 10 1000 NS pH NS NS 5.0-8.0 ° 10 1 0.1 Resistivity (MO-cm @ 25 () min. Si02 mg/I max. 0.05 0.1 1 Particulate matter 0.2 µm filter NS NS Organic contaminants Activated carbon, NS NS distillation or reverse osmosis 45 Dedicated to Discovery PURE LABWATER GUIDE Clinical Laboratory Special Reagent Water (SRW) such as cell culture, organ testing, Reagent Water (CLRW) Required for special clinical and fluorescent antibody detection CLRW water is expected to satisfy laboratory testing, special of microorganisms the requirements of most routine reagent water is pure water with • Low CO2 water may be required clinical laboratory testing. The limits different and usually higher purity to prepare standard buffers for pH specified for the parameters must be specifications from CLRW. The calibration met at the point where the water exits specification should include the same a purification system for storage or parameters as CLRW with additional Instrument feed water use. The specifications are intended ones if required. It may be necessary Instrument feed water is intended to monitor critical parameters to for a laboratory to have a number for the internal rinsing, dilution and adequately ensure purified water for of different SRWs. In most cases a water bath functions of automated the specific clinical laboratory testing SRW is qualified as fit for purpose instruments. Use of CLRW for this procedures. It is mandatory that the for an application by testing during application must be confirmed final product water meets the impurity assay development using techniques with the manufacturer of a specific specifications, and that the parameters such as specimen blank response, instrument and water of this are monitored on a regular basis for reagent blank response, standards specification must be used. trends that would indicate deterioration additions, and interference testing. CLSI emphasises ensuring that in the water purification process. Once qualified, the laboratory needs laboratory water is suitable for its use. An important aspect regarding to define the specifications and The purified water must be validated standards is highlighted in the validation testing to ensure the water as fit for purpose for each laboratory CLSI guidelines. It emphasises that meets its specialised clinical testing procedure in which it is to be used. The prescribed standards can only be requirement. Common applications system producing purified water must for a SRW include: indicators of what is likely to be an also be validated. Regular monitoring, acceptable grade of pure water. It • Trace organic analysis, which trending and documentation of is the responsibility of the analyser may require a lower TOC or a UV appropriate parameters must be carried manufacturer to ensure that a spectrophotometric absorbance out to verify that water purification particular grade or specification of specification technologies and systems are working purified water is suitable for the • DNA and RNA testing which typically effectively. Procedures must be specific chemistry application on a requires DNase, RNase and protease established for system maintenance. particular analyser. free water. Only one grade, Clinical Laboratory Reagent Water (CLRW) is defined in Since chemistry, etc. can be modified, • Trace metals analysis which requires detail. Other grades are described in or new parameters introduced, the a negative blank response for each relation to their application and user- only ‘safe’ option is to provide the best metal to be measured defined in detail. quality water for all applications. Even then for certain chemistries specific • Low endotoxin water (0.25 EU ml or impurities must be highlighted if they lower) may be necessary for sensitive have been shown to affect the results. molecular biological applications 46 Dedicated to Discovery PURE LABWATER GUIDE International Organization for be produced by further treatment quantities. Can be produced by multiple Standardization specification for of grade 2 water, for example by distillation, ion exchange or reverse water for laboratory use ISO 3696: reverse osmosis or ion exchange, osmosis followed by distillation. 1987 followed by filtration through a Grade 3 This standard covers three grades of membrane filter of pore size 0.2 Suitable for most laboratory wet water as follows: μm to remove particle matter, or chemistry work and preparation of Grade 1 re-distillation from a fused silica reagent solutions. Can be produced Essentially free from dissolved apparatus. by single distillation, ion exchange or reverse osmosis. Unless otherwise or colloidal ionic and organic Grade 2 contaminants. It is suitable for Very low inorganic, organic or colloidal specified, it should be used for ordinary the most stringent analytical contaminants and suitable for sensitive analytical work. requirements including those analytical purposes including atomic of high performance liquid absorption spectrometry (AAS) and the chromatography (HPLC). It should determination of constituents in trace Parameter Grade 1 Grade 2 Grade 3 ° N/A N/A 5.0 to 7.5 pH value at 25 C inclusive range ° 0.1 1.0 5.0 Electrical conductivity µS/cm 25 (,max. Oxidizable matter Oxygen (O ) content N/A 0.08 0.4 2 mg/I max. Absorbance at 254 nm and 1cm optical 0.001 0.01 Not specified path length, absorbance units, max. Residue after evaporation on heating at N/A 1 2 110°c mg/kg, max. Silica (SiO ) content mg/I, max. 0.0, O.Q2 Not specified 2 American Society for Testing and Materials (ASTM) D1193-06 Standard specification for Reagent Grade Water This specification covers requirements for water suitable for use in methods of chemical analysis and physical testing, the choice of one of the various grades being designated by the method or the investigator. When bacterial levels need to be controlled, reagent grade types should be: 47 Dedicated to Discovery PURE LABWATER GUIDE Pharmacopoeia standards Pharmacopoeia requirements for ‘purified water’ Separate pharmacopoeias are produced by a number of authorities, notably in the USA, Europe and Japan. Each specifies materials, including water, to be used in medical work. The general purity level of water specified is similar in each case but differs in detail. Extra criteria are set for water required for sterile applications. The standards for purified water given in the European Pharmacopoeia (EP) and in the US Pharmacopoeia (USP) are summarised below. Water for injection into humans or other animals has stringent bacterial/ pyrogen criteria and methods of preparation are specified. European standard EN285 Suggested maximum vales for contaminants in feed to large European standard steam sterilisers (EN285) EN285:2006+A1:2008 specifies requirements and the relevant tests Feed water for large steam sterilisers having Residue on evaporation ,;70mg/l a chamber volume of at least 60 L. Silicate (SiO ) ,;lmg/1 These are primarily used in healthcare 2 for the sterilisation of medical devices Iron ,;0.2 mg/I and their accessories and also during Cadmium ,;0.005 mg/I the commercial production of medical Lead ,;0.05 mg/I devices. It suggests maximum values Rest of heavy metals except iron, cadmium, lead ,;0.lmg/1 for contaminants in the water feeding such units. Chloride (Cl) ,s2mg/l Phosphate (P Os) ,s0.5 mg/I , ° ,s 5 µSiem Conductivity (at 25 C) pH value (degree of acidity) 5 to 7.5 Appearance Colourless clean without sediment Hardness ( I Ions of alkaline earth) ,s 0.02 mmol/1 NOTE Compliance should be tested in accordance with acknowledged analytical methods. 48 Dedicated to Discovery PURE LABWATER GUIDE Glossary 49 Dedicated to Discovery PURE LABWATER GUIDE Absorption A process by which Colloid A stable dispersion of fine Endotoxin Units (IU/ml or EU/l) asubstance is taken up chemically particles in water that have a A quantification of endotoxin levels or physically in bulk by a material typical size less than 0.1 μm. Colloids relative to a specific quantity of (absorbent) and held in pores or containing iron, aluminium, silica reference endotoxin. 1 EU/ml is interstices in the interior. and organics are commonly found in approximately equal to 0.1 ng/ml. natural and potable waters. Activated Carbon A highly porous Epifluorescence form of carbon used for sorption of Concentrate The liquid containing Method of fluorescence microscopy organics and removal of chlorine and dissolved and suspended matter that which can be used to detect bacteria chloramine. concentrates on the inlet side of a after filtration and staining. membrane and flows to drain. Adsorption Adherence of molecules, Feedwater The water that is atoms and ionised species of gas Condenser The stage of a distillation introduced into a purification process. or liquid to the surface of another system that removes sufficient heat Filtration A purification process in substance (solid or liquid) as the result from a vaporised liquid to cause the which the passage of fluid through a of a variety of weak attractions. vapour to change to a liquid phase. porous material results in the removal Anion Exchange Resin An ion exchange Conductivity Conductivity is the of impurities. resin with immobilized positively reciprocal of resistivity. For water Fines particulates released from a charged exchange sites, which can purification systems, conductivity is bed of material such as ion exchange bind negatively charged ionised usually reported as microSiemens per resins. species, anions. centimeter (μS/cm) at 25°C. Azeotrope A blend of two or more Degassing The removal of O and CO Fouling Index See Silt Density Index. 2 2 components with equilibrium vapour from water, usually by transfer across Gram-negative refers to bacteria that phase and liquid phase compositions a hydrophobic membrane. CO is do not absorb a violet stain originally 2 that are the same at a given removed to increase down stream ion described by Gram. temperature and pressure. exchange capacity. Hardness The scale-forming and Bactericide A chemical or physical Deionisation (DI) Removal of impurity lather-inhibiting qualities of some agent that kills bacteria. ions from water. Usually used to refer water supplies, caused by high Biocide A chemical or physical agent to ion exchange – see Ion Exchange. concentrations of calcium and that kills microorganisms. Distillation A purification process magnesium. Temporary hardness, caused by the presence of magnesium Biofilm A layer of microorganisms that takes advantage of changing or calcium bicarbonate, is so called enclosed in a glycoprotein the phase of a substance from liquid because it may be removed by boiling polysaccharide matrix, which are to vapour and back to liquid usually the water to convert the bicarbonates adherent to each other and/or to at the boiling temperature of the to the insoluble carbonates. Calcium surfaces. substance, in order to separate it from and magnesium sulfates and other substances with higher or lower Carbon Fines Very small particles chlorides cause permanent hardness. boiling points. of carbon that may wash out of an Ion Any non-aggregated particle of activated carbon bed. Electrodeionisation (EDI) Technology less than colloidal size possessing combining ion exchange resins and Cartridge A pre-packed disposable ion-selective membranes with direct either a positive or a negative electric container for housing a water charge. current to remove impurity ionized purification resin, media or membrane. species from water. Ion Exchange (IX) The process of Cation Exchange Resin An ion purifying water by removing ionized Endotoxin A thermally stable exchange resin with immobilized salts from solution, by replacing lipopolysaccharide component from negatively charged exchange sites, hydrogen ions for cation impurities the cell wall of viable or non-viable which can bind positively charged and hydroxyl ions for anion impurities. gram-negative microorganisms. Can ionised species (cations). act as a pyrogen. Line Cell An electrode assembly CFU/ml Colony Forming Units per inserted into a water stream by milliliter. A measure of viable microbial which the conductivity or resistivity is populations. measured. 50 Dedicated to Discovery PURE LABWATER GUIDE Microorganism Any organism that is Pyrogen A category of substances, Total Dissolved Solids (TDS) A measure too small to be viewed by the unaided including bacterial endotoxins, which of the total of organic and inorganic eye, such as bacteria, viruses, molds, may cause a fever when injected or salts dissolved in water, obtained by yeast, protozoa, and some fungi and infused. drying residue at 180°C. algae. Regeneration The method by which Total Organic Carbon (TOC) Total Off-line In water monitoring systems, exhausted ion exchange resins are concentration of carbon present in referring to measurement devices reactivated by treatment with strong organic compounds. that are not directly coupled to the acid or alkali. Turbidity The degree of cloudiness water stream. Resistivity The electrical resistance of water caused by the presence On-line In water monitoring systems, between opposite faces of a of suspended particles or colloidal referring to measurement devices onecentimeter cube of a given material material. Turbidity reduces the directly coupled to the water stream. at a specified temperature. Resistivity transmission of light and is measured is the reciprocal of conductivity. For in Nephelometric Turbidity Units Particulates Discrete quantities of water analysis, resistivity is usually (NTU). solid matter dispersed in water. reported in megohm-centimeters Ultrafiltration A process in which Permeate The purified solution (MΩ-cm) and corrected to the value at water is filtered through a polymeric which has been produced by passage 25°C. All resistivity values referred to in membrane having a very fine pore through a semi-permeable reverse this guide are at 25°C unless otherwise structure. osmosis membrane. stated. Ultra-violet (Photochemical) pH A measure of the acidity or Reservoir In water purification Oxidation A process using short alkalinity of a solution equal to –log systems, a container holding + wavelength light to cleave or oxidise [H ]. quantities of purified water. organic molecules. Photo-oxidation See Ultra Violet Reverse Osmosis (RO) A process in Validation Confirmation, through the (Photochemical) Oxidation. which water is forced under pressure provision of objective evidence, that Planktonic Used to describe aquatic through a semipermeable membrane requirements for a specific intended microorganisms that float. leaving behind dissolved organic, use or application have been fulfilled. dissolved ionic and suspended Point of Use A dispense point from impurities. a purified water system from which water can be taken. Sanitisation Chemical and/ or physical processes used to kill microorganisms Polishing The final treatment stage(s) and reduce contamination from of a water purification system. microorganisms. PPB Parts per billion is a unit equal Silt Density Index also called the to microgram per kilogram of water. Fouling Index (FI) is a test used to Numerically ppb are equivalent to estimate the potential of the water microgram per liter in dilute aqueous to block filters, derived from the rate solutions. of blockage of a 0.45 μm filter under PPM Parts per million is a unit equal standard conditions. to milligram per kilogram of water. Softening A water treatment Numerically ppm are equivalent to process whereby cations, notably milligram per liter in dilute aqueous hardnessforming calcium and solutions. magnesium ions, are exchanged for PPT Parts per trillion is a unit equal sodium using cation exchange resins to nanogram per kilogram of water. in the sodium form. Numerically ppt are equivalent to Sterilisation Destruction or removal of nanogram per liter in dilute aqueous all living microorganisms. solutions. 51 Dedicated to Discovery PURE LABWATER GUIDE Further reading There are no books in English focusing specifically on pure water for laboratories. The Ultra pure Water Journal (Tall Oaks Publishing) contains articles of interest, as do two books by T.H. Melltzer from the same publisher: High Purity Water Preparation for the Semiconductor, Pharmaceutical and Power Industries (1993) and Pharmaceutical Water Systems (1996). Also, the Handbook of Water Purification, edited by Walter Lorch, published by McGraw Hill. Water Treatment Handbook – Degr. mont, published by Lavoisier. Many of the ASTM standards are relevant to purified water (www.astm.org). Information on water treatment can be found at www.groupve.com and www.elgalabwater.com Dedicated to Discovery At ELGA we are absolute specialists in the dedicated to the supply of pure and ultra pure engineering, service and support of water water systems that help our customers deliver purification systems. Providing scientists and their work uninterrupted. researchers around the world with reliable We have extensive experience in meeting the solutions that deliver absolute certainty in challenges that arise during the development, the quality of pure and ultra pure water installation and servicing of single point-of- for their work. use water purification systems as well as large As part of Veolia – the world’s largest projects involving consultation with architects, environmental orgainsation – we are consultants and clients. COMMITM ENT TO SUSTAINABILITY We can calculate the carbon value of all our products throughout their lifetime and we can supply this information to our customers and partners. Get in touch with us via our website page www.elgalabwater.com/contact. To find out more about our sustainability efforts visit: www.elgalabwater.com/sc CONTACT US ELGA offices and distributors are located in more than 60 countries and are fully trained in all ELGA systems. To find your nearest ELGA representative, go to www.elgalabwater.com and select your country for contact details. ELGA G LOBAL OPERATIONS CENTRE tel: +44 (0) 203 567 7300 fax: +44 (0) 203 567 7205 info@elgalabwater.com www.elgalabwater.com ELGA is the global laboratory water brand name of Veolia. The information contained in this document is the property of VWS (UK) Ltd, trading as ELGA LabWater, and is supplied without liability for errors or omissions. VWS (UK) Ltd. 2019 – All rights reserved. ELGA. and MEDICA. are registered trademarks of VWS (UK) Ltd. P001_ELGA Brand DNA.
