Water-Purification Systems Are An Essential Ingredient To Lab Success

Ordinary tap water contains a variety of impurities, including dissolved organics, inorganics, and gases; suspended particles; numerous microorganisms; and pyrogens, or endotoxins--the byproducts of bacterial degredation. Although the actual types and amounts of contaminants often vary with geographic location, seasonal cycles, and other factors, they are all considered by researchers to be detrimental to life-sciences investigations and must be eliminated. Six basic water-purification technologies--distillation, ion exchange, carbon adsorption, reverse osmosis, microporous membrane filtration, and ultrafiltration--represent the standard methods for removing impurities. However, because some of these procedures tend to remove only a single type of contaminant, an effective water purification system should consist of a combination of techniques to achieve the desired water quality, industry experts recommend. "If you look at the bulk flow of water, starting with tap water coming into the laboratory, about 90 to 99 percent of the particles, dissolved ions, organics, and bacteria should be removed in a pretreatment stage," says Byron Stewart, a product manager in the laboratory water division of Bedford, Mass.-based Millipore Corp. "This process could be reverse osmosis, distillation, or deionization." A polishing stage to remove trace levels of contaminants is required to produce the highest-quality, ultrapure water and is recommended as a final treatment for most life-sciences applications, taking the water to an ultrapure level of quality, he explains. These recommendations are apparently being followed by many life-sciences researchers. "We require really good lab water because our cells are very susceptible to any sort of contamination," notes Robert Stolen, a senior microbiologist at the Wisconsin Animal Health Laboratory, located in Madison. Stolen does a lot of viral work using living cell cultures as indicators for isolation and serum neutralization procedures. "If we saw any changes in our cell growth patterns, one of the first things we would check is our water supply," he points out. But Stolen says his final-stage polishing system is very effective in removing any contaminants that might be in the tap water line. It has a carbon filter that removes organics and gases, two deionizing cartridges to remove dissolved inorganics, and an ultrafilter that takes care of microorganisms, particulates, and pyrogens to yield Type I (18 megohm-cm) reagent-grade water. The unit, which delivers high-quality water at the rate of 2 liters per minute, also has a remote dispensing gun with a six-foot flexible tether. "This feature really makes it convenient to dispense water directly into our various carboys and flasks," he adds. Stolen's water supply actually causes him very little concern because his water-purification system is so effective in removing all of the unwanted impurities, he contends. "Even if the unit's critical LED monitor lights were to fail, our cells are such good indicators, they could tell us the quality of the effluent water," Stolen remarks. Stephen Foundling, an assistant professor at the Oklahoma Medical Research Foundation in Oklahoma City, also emphasizes the importance of water quality in his protein crystallography laboratory. "We must start with ultra-high-purity water, and add mixtures of salts and buffers in an analytical manner to achieve our crystallizations," he explains. To ensure that he receives only high-quality water, Foundling has installed in-line conductivity systems to continuously monitor water purity. Pure water is absolutely essential in Foudling's laboratory, where several AIDS- and cancer-related projects aimed at assisting immunosuppressed or immunocompromised patients are in progress. For example, he says, "We are actually growing the strains of Candida yeast that cause infections, and isolating the enzymes that are involved in breaking of down the skin barrier." He looks forward to the development of a rational drug-design program for specific drugs and ligands that will bind to these enzymes and prevent breaking the skin barrier. Rick Passanisi, a product manager at Barnstead/Thermolyne Corp., located in Dubuque, Iowa, points out a few other considerations in achieving high-purity water in the laboratory. "The presence of heavy-metal ions is very serious to life scientists because it could cause cells to mutate, or could severely retard their ability to replicate," he cautions. To avoid this problem, he recommends using water-purification systems with proper mixed-bed deionization cartridges to completely remove heavy-metal contamination. Passanisi also advises against the storage of high-quality water: "If the water is not properly treated and stored in appropriate vessels, it can grow bacteria. They will then go through their life cycle, releasing pyrogens and causing extensive problems for the user." Within the last five years, researchers have been seeking ways of excluding specific contaminants, such as proteins and organics, that interfere with their work. To meet these needs, a new system utilizes bundles of small-diameter hollow fibers, through which water is purified and collected from the fibers' inner walls. Scientists are achieving remarkable results with this system, including a tremendous reduction in pyrogens, effective removal of nucleases, and organic levels measuring only a few parts per billion. This technique is being used in many life-sciences applications, including recombinant DNA, polymerase chain reaction, in vitro fertilization, and the preparation of electrophoresis gels. "We cannot grow embryos in media made from water containing endotoxins," says Kathy Sharpe-Timms, the director of Assisted Reproduction Laboratories at the University of Missouri in Columbia. "It's extremely important for us to have high-quality water." Clearly, there is too great a risk for Sharpe-Timms to rely solely on the ability of her purification system to consistently dispense the quality of water she requires. In addition to closely monitoring the built-in indicators on the system, she and her staff perform a series of special bioassays for added quality assurance immediately prior to using the water for one of their human reproduction applications. "If there is a problem with the water, it will definitely show up in one of these tests," she states. Sharpe-Timms recognizes the benefit of the recirculation feature on her system. The high-quality water recirculates through the purification process on a regular basis, she says. "If there were a holding tank," she remarks, "I would always be concerned about what's growing inside." Understanding that filter longevity is critical to the operation of the water-purification system, Sharpe-Timms is very satisfied with the performance of her unit's filter system. "Although we may have to change the hollow-fiber filter every few months, the big set of filters, which represents the greatest expense after the purchase of the equipment, functions very well for up to a year," she says. Other researchers also acknowledge the service that the filters in their water system provide. "We have kept the same hollow-fiber filters in use for over six months and have never had a decrease in flow," notes Robert Meeker, a senior laboratory manager in the toxicology department at the Environmental and Occupational Health Sciences Institute in Piscataway, N.J. Because he works in molecular toxicology, Meeker requires high-purity water for his studies in determining how environmental chemicals affect genes and regulate DNA and RNA. He notes that not all water-purification systems maintain the same quality, and it's important to really check them out thoroughly. For example, he says, "I found that the central water-purification system in our building is loaded with bacteria and slime. By comparison, the inside of our lab system is squeaky clean." That may explain why people from nearby labs have been pilfering water from his supply for their own experiments, he speculates. The hollow-fiber technique is also being used to purify water for nutraceutical research in the prevention of age-related diseases. "Since water is a reagent in our diagnostic clinical-assay systems, it must be very high purity. We don't want it to be another variable in our investigations," says Robert Barry, research director at Boston-based Odyssey Therapeutics. Neutraceutical research involves naturally derived substances that have health-related benefits, he explains. A lot of people tend to forget that water is a formidable reagent, and could be a source of contamination, he notes. To make his point, Barry relates an incident in which a discrepancy in results occurred during a research project being conducted by two laboratories thousands of miles apart. After nine exhausting months of checking every chemical, reagent, and control, they finally discovered their problem: It was the water.

Water-Purification Systems Are An Essential Ingredient To Lab Success

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