Laboratory water purification systems get no respect. They’re used every day, but few lab workers realize— beyond opening the spigot— how they operate.
“The level of knowledge in the average lab about lab water is not very high,” says Julie Akana, Ph.D., product manager for water purification products at Thermo Fisher Scientific (Ashville, NC).
Pure water is classified, in order of decreasing purity, as Type 1, Type 2, and Type 3. Culture media, clinical laboratory analyzers, and buffer preparation get by nicely with Type 2 water, which also serves as feedstock for Type 1 purification systems. Labs use Type 3 “pure” water for labware washing and rinsing and for heating and cooling devices in which mineral deposits from circulating water are a problem.
Common techniques for water purification include distillation, filtration, deionization, electrodeionization, reverse osmosis, adsorption, and ultraviolet oxidation. Distillation is the oldest method and the broadest in terms of impurity removal, but even the best stills produce “only” Type 2 water, and reverse osmosis systems, Type 3. Stills (including double- and triple-stills) are still quite common because of their simplicity and the fact they require no consumables.
Nick Papp, president of Aqua Solutions (Jasper, GA), describes distillation as “dead but refusing to get buried.” Distillation includes high energy costs and maintenance and rapid degradation of the product. Most single purification methods excel at one type of removal, e.g., ions, organics, or particles, and individually produce water intermediate between Type 1 and high-end Type 2. Ultrapure water systems combine several of these techniques.
For example, in a high-end ultrapure water system, tap water feeds through a reverse osmosis membrane, then into deionization cartridges, an ultraviolet cell to destroy bacteria and oxidize organics, an activated carbon cartridge to remove the organic by-products of the UV step, and an ultrafiltration membrane to remove pyrogens and nucleases.
Because of budget cuts, institutions are avoiding centralized, sharedresource water purification systems. The paradox is that such systems are probably the most cost-effective, albeit capital-intensive. As a result, business is booming for smaller units suitable for a single lab or group.
“Trends in pure water systems are driven by the capability of analytical instrumentation to detect lower and lower levels of contaminants,” observes Papp. “We’ve essentially gone from part-per-million detection to part-per-billion, so more people are demanding purer water.”
Users, he says, should pay special attention to what they’re using the water for and what species might interfere with their analyses.
Estelle Riche, Ph.D., an applications scientist at EMD Millipore (Billerica, MA) warns about “emerging contaminants” in tap water and their potential impact on ultra-pure water used in laboratories. Those include common prescription and over-the-counter pharmaceuticals, caffeine, herbicides, pesticides, flame retardants, and components of personal- care products.
Given the sensitivity of modern analytical instrumentation, Dr. Riche wonders, “Are these contaminants making their way from the tap into the high purity water used in the laboratory?”
The lesson here is to monitor water, even ultrapure water, for as many contaminants as is practical, and not take conductivity readings as the final arbiter of purity.
- Features a PLC-based controller and highresolution 3.5” HMI, 2-color display
- Provides the user with four customizable easyto- program batch commands
- Provides up to 3.7 liters per minute of 18.2 megohm, 0.2 micron filtered water using a multi-pass ultraviolet system to irradiate water
- Includes a UV-protected dispensing port
Aries Filter Works
- Features a timed dispense mode for walk-away unattended operation
- Yields low levels of organic carbon concentrations for maximum lab water purity
- Pure lab water delivered at a desalination and virus elimination rate of ≥99%
- Activated Carbon Filters add an extra layer of filtration to remove turbidity and chlorine that may damage filter membranes
WaterPro® PS Polishing Stations
- Deliver up to 1.8 liters/minute of Type I water
- Control panel buttons and LED display allow the user to program the system to dispense water for a set period of time from 1 to 99 minutes
- Each model includes a built-in water quality alarm that flashes actual water quality in megohm-cm to alert the user when water quality falls below a set point
Elix® Gulfstream Clinical
- Provides up to 100 liters per hour and 2,000 liters per day of clinical laboratory reagent water (CLRW)
- Features Elix electrodeionization technology to extend purification cartridge life
- Includes reverse osmosis cartridges
- Meets stringent standards of the Clinical and Laboratory Standards Institute (CLSI®) for CLRW