Automated Liquid Handling
Tanuja Koppal

Manual pipetting, even using multi-channel pipettes, is slow, monotonous, variable, and has the potential to cause repetitive stress injuries to laboratory workers. Automated liquid handling systems, on the other hand, are precise, accurate, fast and consistent. They also decrease errors within and between operations, help conserve expensive reagents and rare or hard-to-produce samples and save time.

Liquid handling systems are very diverse in their applications and cater to the throughput and speed of automation that the user needs. They range from single-channel pipetting systems to those with 8-, 96-, or 384-channel pipette heads. Modules are also equipped to handle a wide range of volumes from nanoliters to microliters. Generic operations performed by a liquid handler include serial dilution, plate reformatting, plate replication and array printing. Specialized applications include PCR set-up, whole genome amplification, high-throughput screening, highdensity array printing, cell culture and more. For such specialized applications the liquid handling systems are often coupled to or integrated into other robotic systems. We have liquid handling aspects integrated into a few of our microplate readers, says Joseph Machamer, product manager, Market Development at Molecular Devices (now part of MDS Analytical Technologies). In some assays there is so little time from when the reagent is added to when the signal is generated that you need to have the plate and the optics in close proximity.

In cell culture, the liquid handler is often integrated into the microplate handler and washer to facilitate proper dispensing of reagents and washing of cells. Washers and dispensers to do cell-based assays need to have features and controls that are different and above those that are typically used for biochemical assays, says David M. Donofrio, director, Market Development at Molecular Devices. For cell-based assays the cells have to be kept intact since the signal intensity is intimately tied to the number of cells in a well. Hence, the speeds at which reagents are being dispensed and aspirated become very important. There are systems currently on the market designed specifically for use in either cell-based or biochemical assays. These systems have the appropriate software programs that can control and fine tune variables like dispensing pressure, aspiration pressure, probe height and position, all of which can affect the integrity of the cell layer. However, having one system that can work well for both types of assays would be ideal and is something that is currently being worked on.

Some other factors to consider when choosing a liquid handling system are the systems expandability, ability to operate in an x, y, and/or z direction, fixed or disposable tips and their configuration, volume range, individual channel control, layout flexibility, size and budget. Budget is of course one of the biggest considerations and while the cost of the robotic instrument is certainly important, the cost of consumables for long-term use cannot be overlooked. Most users need to decide up front whether to purchase a liquid handling system that uses fixed or disposable pipette tips. Fixed tips are re-used again and again, so while they might seem like the most cost-effective option, they can cause erroneous results due to sample carryover and are expensive when the entire array must be replaced. While carryover is not a concern for disposable tips, which are replaced after each assay or pipetting function, there is the matter of quality, fit, range, availability and price. Hence, when choosing fixed over disposable tips, the types of samples that will be used, accuracy and precision needed for specific applications, and the length of time the pipettes will be used, are all factors that have to be carefully evaluated.

Another factor is the availability of laboratory space. Some liquid handling workstations are compact enough to be used on a benchtop or inside a laminar hood. Some systems also offer flexibility and multiple configurations for set-up and are more efficient in their use of the available workspace. There are also modular and scalable liquid handing systems can meet the needs of the laboratory now as well as in the future as user needs increase.

Balances
Tanuja Koppal

Balances and scales used in laboratories today come in various shapes and sizes. Although often used interchangeably, scales and balances have different uses. A balance compares the mass of two sets of objects, while a scale determines the mass of an object or set of objects. The most common types in use today are beam balances, spring balances, top-loading balances, analytical balances, precision scales and moisture analyzers.

Spring balances are the simplest type, consisting of a coiled spring suspended from a fixed point with a pan at the other end. Beam balances are used to weigh solids, liquids, powders, and even animals, generally with a capacity from 610 g to 2,610 g; they are often used in classroom situations due to low cost, ease of use and durability. Analytical balances are designed for great precision in quantitative chemical analysis. They yield readability to four decimal places to the right of the decimal point (up to .0001 g). They are extremely sensitive and, since air currents can affect their measurement, must be covered by a draft shield. They are used for samples up to about 320 g. Top-loading balances, which can measure objects up to 200 g, are less expensive but less exacting than analytical balances. They are considered semi-analytical balances, with a readability of up to three decimal places to the right of the decimal point (up to .001 g). Precision balances have a readability of 0.01 g. They produce steady readings in a wider range of environmental conditions than analytical balances, being less sensitive to temperature fluctuations. They can have a capacity from 600 g to 34,000 g.

Microbalances and ultra-microbalances are used to weigh the smallest samples. They offer a capacity of up to 6 g with readability up to seven decimal places to the right of the decimal point (.0000001 g). Moisture balances measure the moisture content in a material sample by using halogen heating with precise weighing technology.

Electronic scales and balances can provide weights in more than a dozen units, including grams, kilograms, pounds, newtons, grains, and ounces, and often in several operating languages. Application modes can be set for statistics, formulation, differential weighing, density determination, pipette calibration, parts counting, animal weighing, check weighing, percent weighing, filling, gross-net-tare weighing, and statistical quality control. Therefore, its important to choose a balance that can report the information specified by the laboratory protocols and quality control systems.

Balances today can be connected to a PC, a data printer, an analytical instrument, or a laboratory robot using serial, parallel, or USB cables. The newest models are equipped with Bluetooth technology, to enable wireless communication. High-contrast backlit displays improve readability and allow accurate readings even in brightly lit conditions. When choosing scales and balances for their laboratories, users should understand that it may be more advantageous to purchase several scales and balances designed for specific applications than to try to find one that can handle all of their needs. They should consider the capacity, resolution, weight, containers, and size of their samples, as well as the speed at which results are needed.

The environment of the lab, operating temperature, humidity, vibration, and ventilation currents can all affect performance. Consequently, its important to keep the balance inside an enclosed space, keep it clean, make sure it is leveled correctly, and make sure it is regularly maintained and serviced. There are also personnel considerations that need to be monitored, such as who will operate and maintain the device and the type of training they have received. Finally, as with any other piece of equipment, it is best to always follow the manufacturers operating instructions, calibration frequency and maintenance recommendations.

Biological Safety Cabinets
Angelo DePalma

Biological safety cabinets (BSCs) are specialized work areas that provide protection to users/operators and/or samples. BSCs are categorized as Class I, Class II or Class III, depending on their construction, airflow characteristics and exhaust systems. These classifications are based on each BSCs suitability for samples at various biosafety levels. Class I and Class II cabinets handle Biosafety Levels 1, 2 and 3 (low to moderate risk), while Class III BSCs are intended for use with Biosafety Level 4 agents (high risk).

BSCs are distinct from other safety enclosures. Laboratory fume hoods pull air over the work item and out into the environment through a vent, whereas controlled atmosphere glove boxes are completely enclosed, protecting both users and samples through an airtight barrier. A distinguishing component of BSCs is their use of high-efficiency particle air (HEPA) filters, which scrub effluent between 99.5 percent and 99.99 percent of airborne particles, or at least 99.97 percent of particles larger than 3 microns.

Class distinctions: Class I BSCs protect personnel and the environment only. Samples are vulnerable because workspace air is swept over them before filtration and venting. Class II cabinets represent a broad category, with varying capabilities that are further subdivided into categories A1, A2, B1 and B2. The main differentiator between Class I and Class II BSCs is that Class II cabinets employ a HEPA-filtered, vertical, unidirectional airflow within the work area. Class III BSCs, which provide the highest level of protection to both workers and samples, are reserved for highly contagious or virulent biological samples.

Class II A2 cabinets are by far the most common BSCs in use today, comprising about 95 percent of installations, according to David Phillips, technical applications specialist at Thermo Scientific (Asheville, N.C.). Class II cabinets have open fronts. Workers are protected by the steady vertical airflow. An ongoing controversy for specifying certain Class II cabinet types involves NSF Standard 49, which states that Class II A2 and B2 cabinets are designed to handle minute amounts of toxic chemicals and radionuclides. But nobody has defined the term minute quantitatively, admits Phillips, who works on the NSF joint committee that determines BSC specifications.

To satisfy whatever that requirement might be, and to err on the side of caution, most laboratories automatically specify the use of Class II B2 cabinets, which Phillips describes as complex, infrastructure sensitive and 10 times trickier to run than Class II A2 cabinets. A lot of people get stuck with B2s, but half of them should never have been installed. Users would be much better served by canopied A2 cabinets.

Jim Hunter, senior project engineer at Labconco (Kansas City, Mo.), suggests using B-type cabinets in situations where workers are consistently working with volatile toxic agents, isotopes or anticancer drugs that you dont want coming back into the lab. Otherwise, the acquisition and operating costs are simply not worth it. B cabinets cost a lot of money and use a lot of energy. Unfortunately, architects assume a B cabinet is always better because its more expensive or because the letter B comes after A in the alphabet. All too often they simply override a customers decision on which type of cabinet to purchase, says Hunter.

As a former certifier of BSCs, Phillips has a unique perspective on the evolution of these cabinets. In the past, he says, cabinets were commodities that barely differed as one considered the product offerings of numerous vendors. They basically all looked like battleships, he says. Beginning in the 1990s, cabinets began incorporating ergonomic designs that allowed operators to move forward and backward in comfort. Enclosures became brighter and air-handling systems quieter (through the adoption of DC motors and computer-controlled airflow compensation). Cabinets evolved from being cookie- cutter-type products to having more choices and options. Its a really fun time to be in this industry, says Phillips.

One improvement affecting both operating costs and the environment is energy consumption. Older-model BSCs were energy hogs, but todays units are downright miserly. Phillips recalls an event at the University of Michigan, where one of his Thermo Fisher colleagues was accused of low-balling the power consumption of a Thermo Fisher BSC. The assembled scientists were forced to eat their words after they tested the product and measured its energy usage. The result was a paper you can find at http://bit.ly/N9bwz.

Environmental concerns have become a huge factor in BSC purchases, according to John Peters, assistant marketing director at NuAire (Plymouth, Minn.). Customers look for energy efficiency as well as total cost of ownership, the life of HEPA filters and the types of motors used to drive the air handlers, he explains. Unlike many other laboratory products, purchasers of BSCs must perform their own due diligence, as no third-party organizations provide energy-efficiency ratings for cabinets.

Laboratory Casework
Tanuja Koppal

Laboratories are complex workplaces and all require easy-to-maintain storage cabinets and countertops with appropriate safety mechanisms in place as well as room to satisfy multiple users. Cabinets and countertops must also fulfill the specific needs of the laboratory in terms of accommodating various types of equipment, and they should be able to withstand long-term exposure to various radioactive, biological, and other hazardous materials to which they may be constantly exposed. Cabinetry, or casework, includes base and wall cabinets, storage and supply cabinets. Other components may include fume hoods, sinks and plumbing options, and power outlets.

Choosing the right laboratory cabinetry depends on a number of criteria, including the type of work being done, safety, durability, budget, and long-term plans. Options range from fixed installations to modular cabinets and mobile units and from custom-designed and installed systems to generic units. Modular cabinets can be adjustable and designed to meet changes in procedures, instrumentation and personnel. Mobile units can be reconfigured by technicians, without the need to wait for maintenance personnel.

Casework can be made of several different materials, including wood, metal, or plastic laminate. Stainless-steel metal cabinets are extremely durable and used in labs with aggressive atmospheres or ones that require decontamination. Wood casework, usually made of oak, birch, or high-grade plywood, is useful in all types of commercial, industrial, and research laboratories. It offers a traditional decor, provides a stable base for equipment, and can withstand decades of use. Plastic laminate is economical and offered in colors and patterns that blend with or accent any decor. Phenolic resin cabinets are very durable and can be used in custom configurations. They are useful in wet or corrosive environments. Polypropylene cabinets, while high in cost, are useful in metal-free and corrosive environments. Mobile benches, made of highgrade steel, can be useful when flexibility and mobility are required. Countertops experience the most day-to-day use, and abuse, in laboratories and should be chosen to withstand the work being conducted. There are more than ten categories of countertop materials used, including epoxy resin, solid phenolics, plastic laminate, stainless steel and natural stone, as well as wood or wood composites, calcium silicate, ceramics and modified plastic composites. Although no material is impervious to everything and suitable for every application, there are a number of options now available that help researchers meet their specifications for unique applications. Casework manufacturers and other vendors often work with researchers to help customize the designs and choose materials best suited for their budgets and applications.

Centrifuges
Angelo DePalma

Centrifuges are among a select group of laboratory instruments that are as scalable as they are configurable. Individuals who have used benchtop centrifuges that handle sub-milliliter volumes may be surprised to learn that centrifugessome as large as roomsare used in industrial processing.

Basic centrifuge designs are simple, consisting of an enclosed compartment inside which a rotor spins rapidly. Rotors, which can usually be interchanged, contain equally spaced openings into which sample tubes are inserted. Samples will either spin at a fixed angle relative to the rotating axis or swing out to perpendicular under centripetal force as the rotor speed increases. Forces generated as the rotor spins cause components in the sample to migrate toward the bottom of the sample tube, according to weight or density.

Entry-level mini-centrifuges easily fit on a benchtop, operate at a single, relatively low speed, generate low gravitational (g) forces, and cost only a few hundred dollars. Minis are used for samples whose components are easily separated by density. Most medical and veterinary office centrifuges are of this type. The next level up, compact benchtop centrifuges, spin tubes of up to about 2 mL and create tens of thousands of gs. Researchers use them to separate DNA, proteins and cellular components.

There are many ways to differentiate centrifuges by type, speed, and features. Beckman Coulter (Fullerton, Calif.), for example, divides its product line into three basic platforms: benchtop devices operating at up to about 10,000 rpm, washing machine centrifuges that provide up to about 100,000 g, and ultracentrifuges that deliver in excess of one million g. In fact, one could argue that all centrifuges exist along a continuum of features that may be mixed and matched, which include g-force generated, sample tube size, refrigeration capabilities, rotation angle, computerization, and others.

Michael Rosenblum, marketing VP at Labnet International (Edison, N.J.), offers the following considerations when purchasing a lab centrifuge:

• What size tubes do you expect to run?
• How fast does your sample need to spin to achieve the desired separation?
• Is an angled rotor or a swing-out rotor best for your application?
• Does your sample require refrigeration?
• What is the range of applications you are likely to encounter?

Angled vs. swing-out tube design affects speed and g-force, and provides sample collection options (spin-out is slower but provides a clean pellet). Refrigeration is desirable because samples heat up during a long run. It all comes down to your expected application range and the likelihood that the instrument you buy will be flexible enough to meet your needs.

Price was conspicuously absent from the list because lab centrifuges tend to be inexpensive compared with other high-use lab instruments. The price sweet spot of about $300 for unrefrigerated, single-speed mini-centrifuges up to about $6,000 for high-speed, refrigerated benchtop instruments covers most applications in the life sciences and other industries.

Because their operation depends on applying physical forces to samples by spinning, centrifuges have not experienced the miniaturization of, say, mass spectrometers or gas chromatographs. But like other lab devices and instrumentation, centrifuges have benefited over the past two decades from advances in computerization and control software. Computerized methods have been particularly useful as biology experiments become more complex and focus on smaller or less easily distinguishable materials. Sample complexity has caused an increase in the use of gradient centrifugation, and the need for computerized methods as well.

Gradient centrifugation uses sucrose, cesium chloride, or some other dense material to separate particles or molecules by weight. The sample is placed on top of the gradient and, as the centrifuge spins the analyte, migrates to the region that matches its density. The analyte may then be removed for further studies. Sucrose gradients, which are the most common, are discontinuous, consisting of layers of sucrose solutions in increasing concentrations. CsCl2 solutions are continuous and permit much finer separation.

There is very little [centrifugation] method development going on in most labs, says Paul Voelcker, centrifugation product manager for Beckman Coulter. People either inherit a protocol that was used for other experiments, or they find it in a paper and adapt it to their conditions. Beckmans Optima eXPert software, which works with the companys ultracentrifuges, allows users to design or optimize protocols by entering the molecular weight, sedimentation coefficient and gradient, and more completely define the run conditions.

Without computerized methods, operators often let a run go much longer than they need to, says Mr. Voelcker. Computerization helps investigators optimize run time, which saves energy and, in the case of labile samples, can help preserve high-value material.

Glassware Washers

Most manufacturers offer standard and large capacity washers and, as with most things, your first consideration should be your actual requirements. In terms of energy efficiency, there is a huge difference in operation costs between a washer that takes 9 gallons to fill and one that takes 15 gallons to fill. When you consider that a wash program is usually 5 or 6 fills, this has a large impact on water consumption, detergent amount needed, electricity needed to heat the water, and water treatment/sewage costs, says Miele Professional Laboratory Division Manager, Ken Austin.

Another efficiency feature to consider is a delay start option which, in places where electricity is less expensive during off-peak hours, facilitates running your washer at night.

Efficient use of time is also important. Cycle times can range from 1 to 3 hours, based on water heat-up times, circulation/spray method and other factors. Consider how important a faster wash program is to your lab.

In addition to capacity and efficiency requirements, you need to consider what types of glassware are used in your lab. Variations in the types of glassware a washer can accommodate now and in the future is an important consideration. Ideally, a washer should accommodate both spindle racks for narrow-neck glassware and open racks that hold baskets for wide-mouth and specialized glassware, such as beakers and Petri dishes, says Jenny Sprung, Product Manager, Labconco Corporation.

Also, be certain that the glassware washer youre considering is not simply a home dishwasher converted to have a DI water rinse cycle. This type of washer cannot be compared with a commercial grade washer that is designed for laboratory applicationsfrom the construction materials (chamber and water path capable of handling 18 megohm 95C pure water), to wash programs designed for organic and inorganic compounds, to pumps with 4 times the circulation rating of a home dishwasher, says Austin.

Since lab glassware may be soiled with a variety of substances some requiring high heat for effective removal and others, such as plastic ware, requiring lower temperatures, a washer with multiple temperature and cycle time options is important. And request that glassware cleaned in your washer has been analyzed for cleanliness, such as with EPA methods for residual metals, volatile and semi-volatile compounds, says Sprung. Also, make sure that the washer is advanced enough to monitor temperatures, dispensing, water flow and other parameters and be able to notify the user if something in the wash process is not correct, which is important in achieving consistent, validated cleaning results, says Austin.

Lastly, consider the noise level of various washers. Knowing the products dBA level, which measures quietness, is important, particularly with large capacity washers. Some brands are very loud, adds Austin.

Incubators
Tanuja Koppal

Laboratory incubators are used to grow and maintain cell cultures and are available in a variety of sizes and types. The incubator market is divided into two main categories: the gassed incubators which are the CO2 incubators, and the non gassed or microbiological incubators. The CO2 incubators are mainly used for cell culture and provide control over factors such as temperature, CO2 for maintaining proper pH levels, and humidity, all of which affect cell growth. CO2 incubators are typically heated to 37C and maintain 95% relative humidity and a CO2 level of 5 percent. Microbiological incubators are essentially temperaturecontrolled ovens that work within the biological range of 5C to 70C and are mostly used for growing and storing bacterial cultures. Most incubator units are water-jacketed, air-jacketed or use direct heat to maintain the temperature around the culture chamber.

Available from 1.4 (table-top) to 40 cubic feet (freezer-like), incubators generally last about 10 years and can be used in a wide variety of applications including cell culture, biochemical studies, hematological studies, pharmaceutical and food processing. Shaking incubators are often used for cell aeration and solubility studies. Refrigerated Biochemical Oxygen Demand (BOD) incubators, with a temperature range of 20C degrees to 45C below ambient, are commonly used for applications such as insect and plant studies, fermentation studies and bacterial culturing.

The cell culture market today is thriving predominantly due to new applications in areas like stem cell research and hence there is more potential for growth in these products, says Douglas Wernerspach, Global Product Manager, CO2 Incubation at Thermo Fisher Scientific. Many manufacturers are working toward addressing some of the common challenges associated with culturing cells, the most important of which is reducing aerial contamination. A number of incubators now offer a high-temperature decontamination cycle that works much like a self-cleaning oven. With the press of a button, the customer can heatsterilize the incubator and get rid of any decontaminants or hazardous spills, says Wernerspach. This option also eliminates the need to take apart individual components for autoclaving. Its convenient, safe, and ensures proper, uniform cleaning that can be recorded as a part of standard operating procedures.

Besides units that can be activated when needed, there are also continuous contamination prevention units that work all the time and do not have to be initiated manually. One technology uses HEPA filtration to continuously cycle the air and remove airborne particulates and contaminants. The other technology that is gaining a lot of interest is the use of incubators that have interiors made of solid copper components. Solid copper or 100% pure copper is naturally antimicrobial and for the first time the U.S. EPA has also recognized copper, a nonchemical, as an effective antimicrobial agent, says Wernerspach. This has led to a number of companies developing copper-based products.

Incubators also come with options that can further increase user ease and convenience. Thermo Fisher has recently introduced a CO2 incubator with an integrated, interactive touch screen display built into the control panel. It has all kinds of built-in user prompts and safety features so that you wont mistakenly change settings and damage the cultures inside, says Wernerspach. It also has the ability to operate in many different languages. Individual users can customize the display to how they want to see it, which helps to minimize user error and training. Additional options include data storage and communications packages that enable data logging to the computer, removable shelves and programmable alarms for temperature set points and duration. At the end of the day what customers really care about is having a reliable unit in which to grow their cells. Hence, the lab environment, the application and the customers comfort level with the technology is what plays a big role in the selection of the equipment. Ultimately you want to go with something that best meets your requirements, says Wernerspach.

Milling and Grinding
Angelo DePalma

Milling and grinding are common operations in the manufacture of foods, chemicals, materials and other products, and equally important at the laboratory scale for analyzing those products, quality control of large processes or preparing samples for analysis.

Grinding may seem low-tech, but after thousands of years of confronting particle size reduction problems, engineers have still not fully characterized the process mathematically. Engineers attempt to predict grinding and milling behavior through a patchwork of three grinding equations: Kicks law (for particles larger than 50 mm in size), Bonds law (about 50 mm down to 0.05 mm) and Rittingers law (below 0.05 mm). Today, academic institutions devote millions of research dollars to grinding and milling; one example is the Rutgers University (New Brunswick, N.J.) Dept. of Chemical Engineerings Mixing in Fluids and Powders Group, headed by Prof. Fernando Muzzio

Grinding and milling remain empirical sciences, says Stanley Goldberg, director at grinding machine distributor Glen Mills (Clifton, N.J.), who prefers the scientific term comminution to size reduction.

Since its hard to predict mathematically how a grinding machine will behave, you have to prove it works on the actual material, with the customers own sample, says Goldberg. Before customers purchase an instrument from Glen Mills, they typically put it through its paces on actual samples, either at their facility or at the vendors.

Patricia Jung, president of particle reduction instrument firm Retsch (Newtown, Pa.), has seen a lot of interest over the past several years from plastics, electronics, pharmaceutical and food companies, and in particular from the renewable energy and nanotechnology industries. Problems with human and pet food supplies have spurred the need for strict quality control measures that involve grinding meal for subsequent analysis. Animal feed companies have to test every shipload, particularly when it comes from overseas, Jung told Lab Manager.

The need for strict particle size control in biofuels and nanomaterials is a relatively recent trend as well, as both industries are in their infancy. Nevertheless, most industries are abandoning manual and other legacy grinding techniques in favor of higher-precision methods that deliver consistent, reproducible results, Jung says.

Pharmaceuticals is another sector where attention to particle sizing is evolving rapidly. Drug firms traditionally micronized active pharmaceutical ingredients to improve blending in pills, tablets or liquid formulations, and to alter how the drug is absorbed. Today, pharma is much more concerned with fine-tuning properties of drugs and other ingredients, to the point where pharmaceutical formulation and nanotechnology overlap. Pharmaceutical quality and development scientists increasingly use particle reduction of raw materials to create suspensions and even solutions.

Maintaining sample integrity is a recurrent theme in milling and grinding, particularly with mechanical milling. The coffee grinder approach to mechanical size reduction works with relatively inert materials such as stone, but introduces heat- and shear-related anomalies for foods, pharmaceuticals and many materials.

One way around this is through jet mills, which propel samples around a chamber at the speed of sound, reducing particle size continuously through high-speed collisions. Since jet mills use no moving parts or screens and generate little heat, they work exceptionally well with heat-sensitive materials.

Cryogenic grinders, also called freezer mills, process materials that are first rendered brittle by exposure to liquid nitrogen, then pulverized. Freezing samples before milling maintains chemical integrity while creating powders from virtually any material. Applications include biotechnology, materials, chemistry, geology, DNA extraction, plant research and pharmaceuticals. The more brittle the material gets when frozen, the finer you can grind it, observes Jung.

Cryogenic milling is possible with any grinding mechanism (e.g., highspeed rotor, impact ball and planetary ball mills) by employing a separate liquid nitrogen bath. Retsch claims to be the only vendor that offers a cryogenic mill that is directly connected to a liquid nitrogen reservoir, a factor that improves safety and convenience.

Nanotechnology has played a huge role in industrys appreciation for smaller particles. As particles approach the 500 nm scale, their color, mechanical and electrical properties change dramatically, observes Goldberg. Classic size reduction equipment cant achieve that level of fineness, at least not economically. Nanotech and stringent demands for particle characterization have driven demand for bead mills that, according to Goldberg, economically achieve nm-sized particles with predictable size distributions.

The rise of nanotech drives two additional trends related to quality and analysis. Materials of construction for milling instruments have become very critical, Goldberg says, because contamination from the instrument is unacceptable in drugs and high-tech electronic or optical nanotechnology. Vendors are therefore moving toward inert product contact surfaces; for example, high-strength zirconia ceramics.

Similarly, nanotech has created an extraordinary need for analysis of very small particles and monitoring of the grinding process itself, particularly in regulated industries. When the field first developed bead mills that could create nanoparticles, no one had instruments that could characterize them, says Goldberg. Today, advanced instruments enable capture of data, related to the milling process, which comprises the quality documentation that accompanies regulatory applications or data sheets.

Particle Size Analyzers
Angelo DePalma

Particle size measurement has become a critical application for chemicals, foods, paints, cosmetics, coatings, materials, and many other industries. Particle size, shape, density and distribution affect the physical properties and chemical behaviors of all products comprised of particles or that use them as ingredients: The size of stationary phase particles affects chromatography retention time, pigment particles dictate hue and finish in paints, and physical dimension imparts mechanical, optical, and electronic properties to nanomaterials. Within critical size domains from nanometers to about 10 microns, the physical state can be as important as chemical composition.

Numerous technologies have emerged for measuring particle size. Sieving and sedimentation, among the oldest methods, provide quantitative sizing from millimeters upward. Optical sizing under a microscope, where particles are visualized and counted against the backdrop of a graticule (grid of evenly-spaced horizontal and vertical lines) and counted manually, is still used for many applications. Microscope-based sizing has been semi-automated through software that counts particles either directly or from photomicrographs

The most sophisticated particle sizing techniques exploit the interaction between light, sound, or electricity and particle analytes. Electroresistive methods rely on the fact that non-electrically-conductive particles reduce the flow of electricity through a conductive fluid. The most common electroresistive particle sizing instrument is the Coulter counter, which quantifies suspended cells. Light- or laser-based techniques measure dimensions and distributions of suspended or, in some cases, dissolved species or particles suspended in air.

Although one of the oldest methods for particle sizingand still the least expensivesieving still serves many industries for particles in the size range up to about 4 mm. Sieving uses various techniques to get particles through the sizing mesh, including oscillation/shaking and sound. Several instrument makers offer sieve-based particle sizing. Most, including Retsch (Haan, Germany) and W.S. Tyler (St. Catharines, ON) and Hosokawa Micron (Summit, NJ), also specialize in particle-generating machines.

Hosokawas particle-sizing devices employ pneumatic sieving, most notably in the Micron Air Jet Sieve product line. The benchtop device, just slightly larger than a test tube agitator, measures particle sizes from 20 to 4,750 microns and serves primarily the food, pharmaceutical, mineral, cement, powder coatings and chemical industries. Laser techniques work best below about 20 microns, says Tim Calvo, Lab Equipment Product Manager.

Micron Air Jet particle size instruments use a large air volume, up to 97 cfm, to pull a negative pressure on the system, which generates an air jet emitted through a rotating nozzle located below the sieving screen. The air flow disperses material atop the sieve and carries the finer particles through the screen and into the collection apparatus. Where systems that rely on oscillating or sound operate through a stack of up to six screens, Micron Air Jet systems use a single screen and perform the analysis in anywhere from 15 seconds to 5 minutes.

Particle sizers that rely on dynamic light scattering (DLS) serve a sweet spot for particle analysis, between 0.6 nm and up to about 6 microns, while laser diffraction operates optimally in the 1-10 micron range. Noting a maxim of measurement science, Jeff Bodycome, Ph.D. of Brookhaven Instruments (Holtsville, NY) observes that life gets more difficult at the extremes. DLS has a broad range for very small particles but once particles get too large, its hopeless. If all your particles are larger than a few microns, youre better off with diffraction and, larger than that, with sieving.

Interest in DLS began in the fine chemical industry, particularly for latex materials used in paint. Today its principal markets are biotech, where it characterizes protein and protein aggregate solutions, and nanomaterials.

It may surprise that DLS uses light at 637 or 660 nm to measure characteristics of species that are much smaller than the wavelength. That is impossible to do with conventional microscopy, for example, whose limit is objects roughly half a wavelength in size. DLS works because it does not detect the molecule or particle, but calculates its hydrodynamic radius as a function of its mobility through the solution. It measures how far the particle moves under Brownian motion, notes Dr. Bodycome. Because this effect is a function of the sixth power of the hydrodynamic radius, DLS picks up species in very low abundance provided they are much larger than the analyte

Purchase decisions for particle size analyzers are based on matching the analyte particle with instrument capabilities. Users with low- or submicron particles will require a light- or laser-based system, while those with larger particles can usually get by with a much less expensive sieve shaker. Quality control labs that analyze samples from large vats of material should consider purchasing separate sample prep equipment, known as a riffler, to improve the likelihood that analysis samples will be representative of the batch. Price is of course a consideration, but users should weigh the consequences of regrinding against instrument acquisition costs, cautions Tim Calvo of Hosokawa.

Pipettes
Angelo DePalma

Pipettes are familiar to any lab worker who needs to transfer small quantities of liquid. Research and development labs in the chemicals, foods, materials, and paints industries use pipettes routinely, but the life sciences arguably consume the largest volume of pipettes and related supplies.

Pipettes come in many varieties, and most feature plastic disposable tips. Note that syringes serve many of the functions of pipettes but tend to be less accurate. Syringes typically are used in situations where the liquid must be delivered to a closed or sealed system, such as a reaction vessel or chromatograph.

While pipettes are handheld, their delivery mechanism may be manual or electronic. Manual delivery refers to the operators thumb depressing or releasing a piston to deliver or withdraw liquid. Electronic pipettes still require the user to activate withdrawal and dispensing, but the work is done by an electric motor.

Pipettes are sold in two basic formats: fixed volume, which always dispenses the same quantity of fluid, and adjustable volume, which delivers a range of volumes. Adjustable pipettes are accurate from about 10 percent up to 100 percent of the volume range. Single-channel pipettes use one tip at a time, whereas multichannel devices hold multiple tips for simultaneously delivering fluids to multiple locations. Biologists who work with microtiter plates, immunoassays or polymerase chain reaction probably will be interested in multichannel pipettes.

The big advantage of electronic pipettes is ergonomics, says Jason March, marketing director at Hamilton (Reno, Nev.). They also allow you to do more; for example, filling the tip once and dispensing multiple times. Those researchers who use pipettes occasionally or who switch volumes often probably are better off with a manual pipette, he advises.

Ergonomics is a huge issue in pipetting. Most vendors, including Hamilton, Mettler Toledo (Columbus, Ohio), VistaLab (Mt. Kisco, N.Y.), Cole- Parmer (Vernon Hills, Ill.), and BrandTech Scientific (Essex, Conn.), manufacture ergonomic pipettes. Theres no denying that excessive repetitive motion can be bad for you, be it in pipetting, typing or other tasks, notes Akbar Anwari, marketing manager at BrandTech. Pipette manufacturers have tried to minimize the forces used in singlechannel pipettes in a number of ways, as Mr. Anwari explained. Reduction of static strain by reducing the pipettes weight and redesigning the device so it drapes over the operators hand instead of being held are two fixes. BrandTech has achieved these through its Transferpette pipette line, for example

Another technique is to reduce the force required to draw liquids. Most pipettes use softer springs or a shorter stroke length to reduce these forces. Anwari claims that the Transferpette line harnesses the power of the muscles used to move the thumb.

Tip ejection forces tend to be the largest forces used on pipettes, especially multichannel pipettes, where tips are ejected eight or 12 at a time. Ergonomic strategies based on lessening these forces reduce the spring tension or involve redesigns that minimize contact between the tip and the tip cone. But if theres too little contact, the tip either will not seal properly or will not sit straight on the tip cone. Manufacturers have attempted to solve this problem by introducing O-rings or V-rings to reduce the forces required to obtain a good seal but that allow the tip to be ejected more easily. Another innovation for multichannel pipettes involves ejecting tips two at a time rather than eight or 12 at a time. Mr. Anwari also believes that nonergonomic design features can make pipettes easier to use. For example, positioning the display so it is not covered by the hand during use reduces the need to shift the instrument to verify volume settings. Another feature is the ability to adjust the volume with one hand without shifting the device.

Accuracy and precision are the two major factors that play into pipette purchases, says Mark Dostalek, marketing communications manager for Gilson (Middleton, Wis.). Customers have to know that theyre aliquoting the right volume. Like other laboratory devices, pipettes must be calibrated and validated for the type of work they do, particularly in regulated industries. Pharmaceutical and biotech work, for example, is done under Good Laboratory Practices (GLP), which is a regulatory designation. Many end users today choose motorized electronic pipettes for GLP work. The devices record volumes and number of cycles and even can provide out-of-specification warnings.

Plus, once you introduce a motor, you can do things like mixing within the tip, reverse-pipetting, and interfacing with a computer to track data and calibration intervals and perform advanced maintenance.

Vacuum Pumps
Tanuja Koppal

Vacuum is an integral part of many laboratory processes, but costs associated with generating a vacuum, such as process costs, user costs and cost to the environment, have never really been considered seriously. Although technology has advanced to provide smaller, cleaner and quieter options, not many people are taking advantage of it. Vacuum pumps last a long time and many people go through their careers without actually buying one, says Peter Coffey, vice president of sales and marketing at Vaccubrand Inc. Hence, people tend to replace their vacuum pumps with what they have used before and not take the time to find out about the alternatives.

Vacuum pumps used in laboratories can be classified into two main typesrotary vane pumps, sometimes referred to as oil-lubricated pumps, and dry (oil-free) pumps. They operate in different ways to create vacuum and aspirate fluids. Centrifugal pumps use centrifugal force to push the fluid through an outlet; metering pumps, such as diaphragm, peristaltic, piston and syringe pumps, pull fluid into a chamber and then push it through the outlet valve; while positive displacement pumps use bellows, piston, rotary lobe and rotary vane to push fluid through a cavity, leaving a vacuum that pulls in more fluid.

Oil-lubricated pumps have been around for many decades, while the oil-free diaphragm pumps are a more recent addition. Although oil-free pumps tend to be one and a half to two times more expensive than oil pumps, there are a lot of advantages to their use as well as significant lifetime savings. First of all, no oil is used, and therefore there is no cause for oil contamination and no necessity for oil change or disposal. Oil-free pumps can be built to be corrosion resistant and hence do not require regular maintenance. Service intervals on better oil-free pumps exceed 10,000 operating hours, says Coffey. If you use your vacuum pump 20 hours a week, 50 weeks a year, thats 10 years before the first scheduled service!

The other misunderstanding that leads to the choice of an oil-lubricated pump is that people think that more vacuum is always better. Oil-free diaphragm vacuum pumps can provide vacuum levels from atmosphere to below 0.5 mbar/torr, whereas oil-lubricated pumps offer high capacities and higher vacuum levels up to 10-3 mbar/torr. What is more important is matching the vacuum to the application, and almost any application can now be performed using an oil-free pump, with the exception of freeze-drying, says Coffey

For certain applications he also recommends considering buying a pump with controls that provide a good balance of speed and control. Even manual controls are better than none, but electronic controls offer huge productivity advantages, he says. In many applications, the type of vacuum control used will determine how much scientist time is needed for oversight and how fast the application proceeds.

It is often very helpful to talk to someone from a vacuum pump company, who can recommend a pump and offer a demonstration about what will be right for your application and budget. There are also interactive online vacuum pump selection guides available that ask a few questions about the planned use for the pump and recommend a series of pumps to satisfy a range of budgets. It is not a glamorous technology but it is one that can affect the costs, comfort and convenience of your laboratory, says Coffey.

Water Baths

Water baths maintain samples at constant temperatureusually above ambient, but cooling is possible as well. Compared with heating mantles and hot plates, water baths provide tight temperature control. Leading manufacturers of water baths include Julabo, Boekel Scientific, Brookfield Engineering, AquaLogic, Sheldon Manufacturing, Techne, VWR, and Fisher Scientific.

Many water bath applications, particularly in the life sciences, also employ some sort of shaking or agitation. Devices incorporating these features, known as water bath shakers, are used for thawing and warming, hybridization, enzyme assays, gel staining, and cell culture. The popularity of water baths has waned somewhat with the advance of accurate, precise incubators, but water baths have the dual advantages of higher sample capacity and wider operating temperature range. Where incubator working temperatures top out at around 80C, baths operate up to 100C. In addition, water baths may be cooled through the addition of an optional external chiller. Several vendors, including Techne, Brookfield Engineering, VWR, and Thermo Scientific offer built-in refrigeration in circulating-style water baths.

The ability to replenish water as it evaporates is a feature of most modern water baths, although some lower-end units still require manual replacement. Another critical feature is precise temperature control, says Rick Passanisi, product manager for shaker baths at New Brunswick Scientific (NBS; Edison, NJ). New Brunswicks Innova 3100, is typical of high-end units. The 3100 incorporates auto-fill, adjustable level control, operating temperatures from 5C above ambient to 100C, and temperature control to within 0.1C. Even low- to midrange bath shakers employ microprocessor control of both temperature and shaking.

One knock against water baths is they can become messy as minerals build up in the water through evaporation. Also, baths turned off at night become breeding grounds for bacteria, yeast, and fungi. Maintenance consisting of replenishing and replacing water, and adding a biocide to inhibit microorganism growth is a minor but persistent issue. Bath-style heating devices employing oils, ionic fluids, and metal alloys are more common in chemistry and physics labs than in the life sciences. Other interesting alternative baths are bead baths, which use metal beads as the heat transmission fluid. Beads provide several advantages over water but are severely limited in their shaking capabilities.

Where water baths work only between that fluids freezing and boiling temperatures, bead baths operate from cryogenic temperatures (-80C) to 300C. Bead baths consume less than a third of the energy of water baths15 watt vs. 50 watt, a consideration if the devices are used constantly. Another environmental concern, disposing of gray wastewater containing biocides and minerals down the sink, is eliminated with bead heaters.

Anyone who has used a conventional water bath has had to deal with wet labware, a possible source of contamination for any type of experiment, but especially troublesome for biology. This issue disappears since metal beads are dry. Another problem with conventional baths is how to support the flask or vial while it sits in a bath of water or liquid nitrogen. Since metal is significantly denser than most labware, vials and tubes may be stood up among the beads with no chance of tipping over.

Beads also provide a measure of portability. Users can scoop out beads in a flask and keep their sample at the desired temperature while they transport it to another location in the lab, notes Rich Jarvis, technical manager at Lab Armor (San Antonio, TX). Samples may also be stored, submerged in a container of metal beads in refrigerators or freezers, and transported in insulated containers. No need to fill a bucket with ice or other coolant when moving samples, Jarvis says. Lab Armor sells beads suitable for use in conventional water baths, as well as bath containers and smaller units that replace heat blocks.

Bead baths can be used in applications that require low-speed agitation by using a standard laboratory rotator (such as a Lab-Line Maxi Rotator, a bead tray, and a general-use incubator.) In one configuration, samples are added to a tray placed atop a rotator inside a laboratory incubator and agitated at the desire temperature. Another option involves using warm beads in an insulated tray rotated on a bench top. In an incubator, the beads transfer thermal energy more efficiently than air alone, and the beads stay at the desired temperature even when the incubator door is opened and closed repeatedly.

Water Purification Systems
Tanuja Koppal

Water is perhaps the most utilized reagent in a laboratory and is often critical for an experiment. As instruments have become more sensitive and applications increasingly complex, the demand for high-purity water has also increased. A few years ago, parts per million (ppm) was a very small level of contamination, but now people are looking for parts-per-billion (ppb) or parts-per-trillion (ppt) levels of contamination, says Renaud Bardon, director for North American Sales Lab Water at Millipore Inc.

There are several types of contaminants in water, such as particulates, organics, inorganics, microorganisms and pyrogens. In the past, people were mainly concerned with ionic contaminants and measured ionic conductivity or resistivity as a way to determine water purity. Today people are more concerned with organic contaminants, particulates and microorganisms, such as bacteria and gases that are dissolved in water, says Bardon.

There are eight commonly used methods to purify water: distillation, deionization, reverse osmosis, activated carbon filtration, microporous filtration, ultrafiltration, ultraviolet oxidation and electrodialysis. The National Committee for Clinical Laboratory Standards (NCCLS) has specified three types of water: I, II and III, as well as special-purpose water, depending on their use. While Type I refers to water with minimal interference and maximum precision to be used for most analytical applications, type III water refers to that used for general washing. The special-purpose water refers to water that has been treated to remove specific contaminants

When selecting the right system for purifying laboratory water, several factors need to be considered. However, according to Bob Applequist, product manager at Labconco, the most important one is to fit the product to the application. You have to differentiate between the need for pure and ultrapure water. In most cases, the pure water generated from tap water can be used for most applications, while ultrapure water generated from a point-of-use system can be used for applications that have more specific and stringent purification needs. The first-step purification or the system that is used to convert tap water into pure water has to be very good and efficient, says Bardon. If you have that first step right, then converting that pure water into ultrapure water is going to be very easy and consistent.

When considering a water purification system, both the quality and the quantity of water have to be taken into account. You have to take into account instantaneous as well as daily water volume requirements, says Bardon. For labs that have variable demands on quality and quantity, flexibility and modularity become very important. The key then is to invest in a flexible system that will meet your needs today and can grow with the lab and change with the applications, says Matthew Hammond, global sales and marketing director for ELGA LabWater.

After choosing the right system, performing regular, preventative maintenance is equally important. The newer versions have built-in alarms and calibrators that warn customers if certain components are coming to the end of their life cycles. Sample the water routinely to make sure that it doesnt contain the impurities that will interfere with your analysis, says Hammond. The level of monitoring can be done daily, weekly or monthly, depending on the stringency of the application and the laboratory environment. Whatever system you buy, make sure its dynamic, so that the water can recirculate regularly, says Hammond. Water needs to be kept moving, as still water ends up building biofilms quicker. So look for a system that is easy to sanitize. If properly maintained and used, most water purification systems can last up to two decades

Finally, ensure that the pure water obtained is being used in the right way. I know of customers who will invest a large amount of money buying an ultrapure water purification system and then dispense that water into a plastic container before they use it, says Hammond. Its an unfortunate truth, but for most people, water is just a utility. Its the most pure reagent that is available at a relatively low cost, and so it often doesnt get the respect it deserves.