Feeding Multiple Operations and Applications
Water is the lifeblood of all laboratories. Purified water, in particular, serves a variety of operations and applications, from wet chemistry to instrumental analysis.
Maricar Tarun, Ph.D., applications scientist at Millipore Corp. (Billerica, MA), explains that lab water comes in three basic types: type 1 (the purest), type 2, and type 3. Type 1 (“ultrapure”) water, the most expensive to produce, is used for highly sensitive analytical techniques with very low detection limits, such as HPLC, LC-MS, GFAA, and ICP-MS. It is also used to prepare buffers and mammalian culture media for cell culture and in vitro fertilization, as well as for molecular biology applications including DNA sequencing and PCR.
Type 2 water is used in general laboratory applications such as buffers, standard pH solutions, and microbiological culture media preparation, as well as to feed clinical analyzers, cell culture incubators, and weatherometers— instruments that allow artificial or accelerated weathering tests. Type 2 water systems are often used to pretreat water for type 1 water systems.
Type 3 water is the lowest laboratory water grade. It is recommended for glassware rinsing, heating baths, filling autoclaves, and to feed higher-grade lab water systems. Types 2 and 3 are referred to as “pure water,” but the gap between these grades and ultrapure is substantial. There may be differentiation even within grades. For example, “water for injection,” a high-purity water with ultra-low bacterial specifications used to formulate pharmaceuticals, runs toward the bottom end of type 2; “triple distilled” water is equivalent to higher-end type 2 water.
Producing type 1 water requires a combination of multiple water purification technologies such as reverse osmosis, deionization, activated carbon treatment, and ultraviolet radiation. “Polishing” systems are fed water from a type 2 or 3 pretreatment system to produce type 1 water.
Units that combine purification technologies are replacing much older distillation systems that predominated two decades ago. Stills remain in place in some labs, notes Paul Whitehead, Ph.D., R&D laboratory manager at ELGA LabWater (Woodridge, IL). “But they’re becoming less popular due to their energy requirements. Besides, most labs need water that is purer than that, particularly with respect to trace impurities and bacteria.” Today’s top water systems produce type 1 water for approximately 15 cents per liter, Dr. Whitehead says—a relative bargain for such a high-quality laboratory product.
Complete water purification systems, which combine pretreatment and polishing in one unit, produce type 1 water directly from tap water. Complete systems eliminate disadvantages of central water purification systems that serve as a pretreatment step. The major drawback of central systems is that they have delivery loops that are complex, expensive, and difficult to maintain or extend. Nevertheless, plant-level systems are popular in large R&D organizations such as pharmaceutical companies.
“A complete system also allows users complete control over all water purification steps and the final water quality,” says Dr. Tarun. “Laboratories that do not have a reliable source of type 2 or 3 water to feed a polishing system can greatly benefit from a single, compact system in any lab with a tap water feed.”
Trends in laboratory water purification technologies are dictated by:
- Advances in instrumentation or applications toward higher sensitivity and analyte selectivity
- The existence of “emerging” contaminants in tap water that may not be efficiently removed by existing purification technologies
- Smaller analysis volume requirements
Dr. Tarun explains that flexibility is another driver. “Many laboratories combine several areas of expertise and, therefore, have a range of applications with specific requirements. For example, one application requires nuclease-free water, while another requires water low in organics.” An ideal water system, she says, should incorporate all these attributes.
Pricing and budget are always considerations at the point of purchase, but other factors are at least as important, for example:
- Applications – What will the pure or ultrapure water be used for? Can the lab get along with type 2 or type 3 water? Does the lab anticipate taking on new applications or workflows that might require type 1 water?
- “Instant” and daily volume needs for ultrapure and pure water
- Feed water available in the laboratory – Does the lab have access to good and reliable central water purification (which could serve as the pretreatment step)?
- Water-quality monitoring needs; for example, resistivity and total organic/ oxidizable carbon (TOC) monitors to ensure that the purification is performing up to specification
- Level of certification required, particularly for firms serving legal or regulated industries
Water purification systems from major vendors operate similarly and produce water at or above advertised specifications. Differentiators, says ELGA’s Paul Whitehead, are ease of use. “Customers like systems with fancier, volumetric dispensing, where the user dials up a volume.”
For additional resources on laboratory water purification systems, including useful articles and a list of manufacturers, visit www.labmanager.com/labwater.
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