Essential “utilities” for analysis and operations
Every laboratory requires high-quality water. Many labs or their parent organizations maintain dedicated plants to transform municipal water into a product lab managers can trust for routine jobs such as glassware rinsing and formulation of non-critical solutions. To take that product to the next level requires a separate, additional process with all its associated duties.
As stills have given way to reverse osmosis, ultrafiltration, and ion exchange technology, water purification has become less laborintensive. Removal of ions, organics, sediment, and even molecular species has become so efficient that end users have become almost as concerned with monitoring or validating the quality of their water as with the purification process itself.
Users and technology factors
Julie Akana, Ph.D., product manager for water purification products at Thermo Fisher Scientific (Waltham, MA), defines water purification trends as user-centered and technology-based. On the tech side, users are interested in more direct monitoring of both product and feed water. With municipal feedstocks of sometimes dubious quality and universities losing funding for pre-treatment plants that feed into ultrapure water systems, lab managers need to be apprised of feedstock water quality. Feed water carrying a high ionic and sediment load significantly reduces the usable lifetime of water purification cartridges.
“Many schools are moving toward all-in-one solutions that take tap water and purify it all the way to ultrapure,” Dr. Akana tells Lab Manager Magazine.
Managers are becoming savvier with respect to total organic content (TOC) as well as sediment and mineral impurities. Some systems today employ an ultraviolet bulb that oxidizes organics, and many employ ultrafilters to remove pyrogens and nucleases. These functions usually come bundled with high-quality water systems, says Dr. Akana, but they also require a higher level of monitoring to achieve conductivity values of 18.2 MΩ•cm at 25°C at less than 5 ppb TOC—the characteristics of ultrapure water.
With pretreatment a differentiating factor, top water system vendors supply test kits or conduct testing to measure impurities that might overwhelm purification cartridges. Thermo Fisher Scientific sells particulate filters, activated carbon for organics, or ion exchange cartridges to remove high levels of certain salts. “We have a diverse bag of technologies to draw upon,” says Dr. Akana, “to customize systems for each user’s situation.”
With carbon monitoring becoming a significant part of water purification, users want assurance that their systems achieve less than 5 ppb of TOC. Thermo Fisher Scientific supplies a UV intensity monitor that sits next to the UV bulb to ensure that the bulb is always properly illuminated. Dr. Akana admits that this is “an expensive add-on” but worth it to ensure that TOC removal is adequate.
Smaller is greener
Shrinking laboratory space has been one driver behind miniaturization of lab equipment and instruments. Water systems have evolved into smaller footprints as well, and many systems today may be located on floors, walls, or in utility areas outside the lab proper. Many systems today have remote dispensing options that allow delivery of ultrapure water some distance from where it is generated. Such systems have alarms and monitors located not on the system but where operators can see them.
Maintaining such systems can be challenging, especially when cartridges are located below lab benches, on raised platforms, or in hallways surrounded by other equipment. Vendors have countered with larger resin cartridges that require less frequent changeout. Some suppliers have cartridge return programs as well, which offer the opportunity to refill an existing cartridge housing.
A related feature is environmentally conscious operation that purifies water with minimal power input and with a smaller carbon footprint. Although it uses electricity to regenerate the module, which avoids throwing an exhausted cartridge into the garbage, electrodeionization (EDI) is thought to be more environmentally friendly than ion exchange. EDI uses small quantities of ion exchange resin that are rapidly and continuously regenerated to their active form with an electrical current.
A difficult squeeze
Vendors say that water systems are becoming easier to maintain, but results vary.
Deborah Hoffer, quality systems manager at Rogosin Institute (Xenia, OH), uses a five-cartridge purification system that delivers pretty close to type 1 water. Her lab works on live cell encapsulation therapy for diabetes and cancer.
Ms. Hoffer’s requirements for purified water are minimal, as her lab purchases critical supplies such as media and buffers already formulated. Yet the quality must be very high since she works in a sterile environment.
Her water system from Millipore (now Siemens) “works as advertised,” but cartridge replacement is tough. “I have a very difficult time accessing them.” Three cartridges are in front of the unit and two are in back. “I have to use a plastic wrench to torque them down, and I’ve broken several.”
Ms. Hoffer’s situation is a bit unusual, as the water system resides in a cleanroom where space is limited.
“It would help if the cartridges could be located outside the cleanroom where they might be more accessible and not require gowning for performing routine service.” Consumables costs are another issue for her lab. Cartridges are replaced twice a year, and the 0.2-micron filter is replaced every week.
Only as strong as its weakest link
No matter how efficiently your purification system removes impurities, the final verdict on water purity is only as favorable as the “dirtiest” operation. According to Bob Applequist, product manager at Labconco (Kansas City, MO), the only way to ensure that purified water is sterile is to transfer it from the purification system to an enclosed container through a closed transfer system. “Ultrapure water should never come into contact with open air.” Aside from sterility, an improperly prepared receiving vessel can introduce enough ions to lower the resistivity by several orders of magnitude. Not every water application demands sterility or 18.2 MΩ•cm quality, but those that do require the utmost care.
Cell culture is one of those critical applications where sterility is mandatory. “Culture media absolutely must be free of bacteria, mold, and viruses, so the water system must deliver its product to a vessel inside a laminar flow system or directly into a sterilized, closed system,” says Mr. Applequist.
Culture labs might also consider an ultrafilter, which removes not just microbes but their cellular products as small as 1,000 daltons.
For additional resources on high-purity laboratory water systems, including useful articles and a list of manufacturers, visit www.labwrench.com/water-purification