FEBRUARY 2004 TODAYS CHEMIST AT WORK 692004 AMERICAN CHEMICAL SOCIETY

PRODUCTPROFILE

The quest for purewater chemistry

For centuries, peoplehave sought pure water.As early as 1450 B.C.E.,Egyptian hieroglyphs docu-ment the clarification ofwater using alum, whichcauses suspended particles tosettle out. From the 1700s,when filtration was primarilyused as a means of removingparticles from water, to thelate 1880s, when Pasteursgerm theory of diseaseexplained how microscopicorganisms could transmitdisease through water, to the21st century, ridding waterof harmful substances hasbeen a focus of society.

Today, water is purified bynumerous processes, such ascarbon adsorption, deioniza-tion, ultrafiltration, reverseosmosis (RO), ion exchange,UV irradiation, and distilla-tion, to remove or neutral-ize impurities so it can beused in industrial applica-tions as well as for humanconsumption (see Table 1).

Distillation, probably theoldest purifying technique,has long been the method ofchoice of the environmentalindustry. Considered to bethe most effective method ofpurification for the removalof inorganic, radioactive, andbiological contaminants,distillation removes a greaternumber of impurities thanany other method. Whilethere are several separationtechniques, distillationcontinues to be a workhorsein the chemical industrybecause of its cost-effective-

ness and ability to producehigh-purity products.

For example, the 611 DIof Sartoriuss Arium line oflaboratory water purificationsystems features a distillationcarbon-resin system thatproduces ultrapure waterwith a resistivity up to18.2 Mcm and totalorganic carbon (TOC) ofless than 4 ppb.

Likewise, RO systemshave been enhanced by im-provements and advances inmembrane technology thathave made it possible to in-crease membrane longevitywith proper use. RO is aneffective, relatively economi-cal solution that removes9099% of all contaminants,especially from brackishwater.

Labconcos WaterPropoint-of-use pure-watersystems can be used incombination with RO setups,

thus extending the life of themembrane. Also, the Water-Pro Polishing Station ensuresboth bacteria-free water andlow TOC levels by using anoptional dual UV reactor.

Similarly, Barnstead hasrecently launched a new

purifier, theEASYpure IIRF/UV Reser-voir Feed Ultra-violet WaterPurificationSystem, whichfeatures anoutput of1 L/min ofwater withresistivity of up to 18.2Mcm andTOC levelsbelow 3 ppb.Applications for this ROsystem include

HPLC and GC-MS for critical organic deter-minant analysis. The seem-ingly endless choice ofproduction devices offerslaboratories convenienceas well as portability.

In ultrafiltration, micro-porous membrane filters actas sieves to separate dissolvedmolecules based on their size.Millipores new Pyrogard Dpoint-of-use ultrafilter phar-maceutical-grade 13 kDmembrane, coupled withMillipore ultrapure-purifica-tion systems and Simplicitysystems, features filtrationmembranes with flow ratesof 600 mL/min on a Milli-Qsystem and 200 mL/min ona Simplicity water purifica-tion system. This utilityaffords scientists the abilityto remove fine particulatebacterial, pyrogen, and nucle-ase contaminants.

K E Y T E R M S : LC, sampleprep, pharmaceutical

Water Purification

Milli-Q consumables. (Image courtesy of Millipore.)

The Sartorius Arium 611 series. (Image courtesy of Sartorius Corp.)

70 TODAYS CHEMIST AT WORK FEBRUARY 2004 www.tcawonline.org

PRODUCT PROFILE

Palls membrane cassettesoffer ultrafiltration andmicrofiltration tangentialflow filtration capabilities.The membranes feature 40%larger feed and retentateports. The larger fluid portdesign promotes a moreuniform transmembrane

pressure profile across thefeed/retentate channels aswell as improved fluid distri-bution and efficient sanitiza-tion of the cassette system.

Likewise, Whatmanshigh-purity cartridge filterdevices offer prefiltrationthrough final filtration

performance. The validatedQMC, QTEC, and VTECpharmaceutical filters help toeliminate bacteria by meetingor exceeding toxicity, endo-toxin, oxidizable, and cytoxi-city requirements.

UV irradiation using amercury lamp as a means of

sanitizing has long been usedas a germicidal treatment forwater. Recent advances intechnology include lampsthat generate both 185- and254-nm UV light.

The introduction of ColeParmers combination filter-UV sterilizer provides scientistsfiltration and sterilization inone unit. The disposable filtra-tion device can be used inbiopharmaceutical and phar-maceutical applications. Itremoves soil, sediment, andchemicals using a 0.5-m porefilter while the UV systemsimultaneously kills 99.9%of bacteria.

Recently, Whatman intro-duced its Polycap GW Cap-sule, which is housed inpolypropylene material fordurability and has been testedusing the EPA Test Method3005 protocols. The capsulehas a large filter surface areaoptimized to provide 600 cm2

of effective filter area to ensurerapid collection of samples. It also has low metal extract-ables and comes with acertification.

Many of the water purifi-cation methods used today inthe chemical, pharmaceuti-cal, biotechnology, and envi-ronmental industries includetechniques that have beenused for years. But becauseeach purification methodremoves a specific type ofcontaminant, a well-designedsystem that uses a combina-tion of purification technolo-gies is critical to achievingfinal water quality. Withproper treatment, the combi-nation of these technologiescan produce virtually micro-bial-, ionic-, and organic-freepure water.

Further ReadingBaker, M. N. The Quest for Pure Water;

American Water Works Association:New York, 1981.

Kimberly S. Cleaves

Company Website Product Mechanism

Barnstead www.barnsteadthermolyne.com DIamond RO Deionization, reverse osmosis

EASYpure II RF/UV Ultraviolet

MEGA-PURE Glass Stills Distillation

NANOpure DIamond Deionization, ultraviolet,

ultrafiltration

Cole Parmer www.coleparmer.com High-capacity UV sterilizers Ultraviolet

Ion-X-Changer filter cartridges Deionization

Laboratory Water Still Distillation

Labconco www.labconco.com WaterPro PS General Chemistry Deionization

WaterPro PS UF Deionization, ultrafiltration,

ultraviolet

WaterPro RO Stations Reverse osmosis

WaterPro Softeners Softening

Meissner www.meissner.com STyLUX PES membrane filter Deionization

Millipore www.millipore.com Elix Deionization, reverse

osmosis, ultraviolet

Pyrogard D Ultrafiltration

RiOs Water Purification Reverse osmosis

Synergy Ultrapure Ultraviolet

Pall www.pall.com Centrasette Ultrafiltration

Disc Tube Module System Reverse osmosis

Ultipor Filter Deionization

Sartorius www.sartorius.com Arium 611 VF Deionization, ultrafiltration,

ultraviolet

Arium 611 UF Deionization, ultrafiltration

Arium 611 UV Deionization, ultraviolet

Arium 611 DI Deionization

Whatman www.whatman.com Polycap GW Capsule Other

US Filter www.usfilter.com Memcor Ultrafiltration

VCD Series Ultraviolet

Vantage Series RO systems Reverse osmosis

Wastewater Ion Exchange Deionization

For a more extensive list, visit www.labguideonline.com.

Table 1. Selected Water Purification Technologies and Systems