get away with more than the indus- trial people can.

"It's going to become a more vexing problem that you simply won't be able to ignore," he adds.

Supercritical fluid extraction pro- cess technology got its start in Ger- many in the late 1970s as a result of the European Community's strong de- sire to phase out the use of toxic meth- ylene chloride, according to Marc Sims, an engineer who heads his own company in Emeryville, CA, involved with the design and construction of industrial SFE plants. This process was especially important in the pro- duction of beer.

In the past few years, food industry conglomerates in the U.S. have shown that SFE, a compression process that uses carbon dioxide to pull substances from solids, can be used to purge com- mercial products of certain ingredi- ents. Philip Morris USA, for example, uses the process to take nicotine out of cigarettes. General Foods decaf- feinates coffee beans with SFE. Brew- eries treat hops with SFE to improve the flavor of their products.

"In addition to the extraction of cof- fee, tobacco, and hops, there is a ma- jor market for the SFE production of extracts used in food flavoring, such as vanilla and ginger," says Sims. "Ex- traction with CO, provides the most

to say that SFE bene- eing explored in the

Antibiotics and steroids are areas of intense research. However, as polarity of the material increases, its solubility decreases dramatically, making it dif- ficult to extract. Specific achievements in this area remain highly confidential because it is so important that compa- nies maintain their competitive ad- vantage,

Now researchers at several U.S. regulatory agencies are d;emonskating that SFE can be used effectively in place of Soxhlet and other organic sol- vent extractions. The-USDA is betting that SFE can take toxic solvents out of the millions of routine extractions that are run in U.S. labs every-gear- extractions that leave behind a'torrent of toxic waste.

More important, now that the tech- nology is available, government regu- lators may soon require research and testing labs to replace their existing extraction systems with techniques

if any, organic sol-

ikelihood is a home- made SFE pilot plant tucked away in the basement of USDA's Northern Regional Research Center, Peoria, IL.

Surrounded by 1.5-ft-thick walls of reinforced concrete, this plumber's nightmare of stainless steel pipes, cy- lindrical chambers, flanges, and

I

sign run a&ok. Every so often, the apparatus shatters the relative silence of the agricultural research lab by re- leasing a breath of carbon dioxide from an'extraction cell-a metal lung rated at 28,000 psi-while a substance resembling baby food dribbles into a collection flask undemeath.

The extracted sample, destined for analysis in a nearby gas chromato- graph, could be almost anything. USDA researchers have loaded Mc- Donald's Quarter Pounders, potatoes, lunch meat, peanut butter, and boiled spinach into the pilot plant to study pestidde amounts in the nation's food

The sample chamber is pressurized with CO, gas to 10,000 psi and heated to 80 C (176 F). These conditions make carbon dioxide unstable. In other words, it becomes a supercritical fluid.

A small change in the pressure of a supercritical fluid causes a big change in its density. The solvent strength of the fluid also changes with changing density. As a result, the su- percritical fluid easily performs the work of many solvents, flowing through a tissue sample and removing specific elements, such as pesticides,

supply.

iupercrit ical fluid ex trac tor from Dionex C o y . is typical of new SFEs. I t offers nultiple cell capability, extraction pressures of up to 10,000 psi, and a unique plug- ?esistant collection technique. Eight cells can be extracted simultaneously.

. ._...

. . .

'I don't think there's any joking about it. Regulators are going to crack down,' says an SFE expert.

have been used successfully as super- critical fluids. However, none offer the superior benefits of C0,-safety, cost, availability, and odorlessness.

SFE can be selective. By adjusting such variables as pressure and tem- perature, SFE can selectively extract materials of. terest from complex ma-

or p ex orm class fractionations. to Jerry King, the USDA chemist designed and built the pilot

lant, the most important thing about !LE is the elimination of toxic organic solvents. While Soxhlet extractors rely, on toxic methylene chloride and ace- tone to separate trace a tiades and other conta samples, supercritical fl use only harmless CO,.

Each supercritical fluid extraction takes about 30 min to perform at a material cost of 10 cents. Soxhlet extraction, on the other hand, may take one hour or more, and its mate- rial cost may be as high as $3.

But Soxhlet extraction's

cide intake, Hopper must find an eco- nomical way to screen the nearly 1,200 Sam les of food he receives each year P rom restaurants and gro- cery stores across the country.

In an average year, the study- which has been performed annually since 1961-will consume the equiva-

solvent as a result of extractions per- formed tion.

~f extractions with USDA's SFE equip- ment, he asked King to build a similar device for the Total Diet Study. Hop- per plans to begin phasing out Soxhlet extraction as soon as the SFE equip- ment is in place.

"As a research chemist, I saw there was a need to try to eliminate sol- vents, and SFE looked like a technol- ogy that might work," Hopper says. "Most analytical chemists are aware of solvent hazards, but at this time,

lent of three 55-gal drums of organic

most significant single drawback is not time or cost. It's the amount of toxic organic solvent you need to use.

The technique requires 450 ml of mixed ether sol- vent to flush contaminants from a single 50-g sample of material. If the sample material contains no fat, which is easy to flush out, the researcher using Soxh- let extraction will need nearly 750 ml of methylene chloride.

Only a fraction of the sol- vent is actually consumed by this process. So a toxic liquid that must be safely packaged and shipped to a designated hazardous waste disposal facility is left behind. At an approximate cost of $250 per 55-gal drum of chlorinated sol- vent, the disposal cost alone is 90 cents per sample.

Marvin Hopper, a re- search chemist at FDA'sJTo- tal Diet Research Center, Kansas City, MO, has a par- ticular stake in King's SFE project. As coordinator of FDA's Total Diet Study, which monitors the average American's annual pesti-

42 R&D Magazine, March 1991

Soxhlet is the only way to d o the job, so that's what they use."

Laboratories nationwide that rely on Soxhlet equipment for sample preparation consume millions of gal- lons of solvent each year to perform EPA-mandated compliance tests, says William Budde, director of chemical research for the U.S. Environmental Protection Agency's laboratory in Cincinnati.

reduce methylene chloride consump- tion in EPA tests by 95% by 1994.

The USDA has even bigger plans for SFE. Analytical chemists at the agency's Food Safety & Service (FSIS), which inspects all meat destined for consumption in the U.S., must screen nearly 100,000 samples every year for pesticides, steroids, and other contaminants. Each sample cur- rently undergoes Soxhlet extraction before analysis.

Four years ago, before solvent use came under fire by the EPA,

S,FE; which uses C 0 2 gas to extract substances from samples, ,& cheaper and cleaner than convenfional solvent-based extrac- tion methods. USDA researchers have shown that Soxhlet extrac- tion costs more than 16 times as much as SFE and generates large quantities of hazardous waste. SFE works as well as Soxhlet techniques and generates no toxic waste, the researchers say.

FSIS coordinato; Michael Hoffman commissioned King to build USDA's SFE pilot plant and screen meat samples for trace amounts of pesticides. As anticipated, King's apparatus and tech- niques worked flawlessly for pesticide extraction. Hoff- man predicts SFE could cut his agency's solvent use by at least 80%.

"At the moment, it's un- known what SFE's limita- tions are," he says.

Happily, analytical instru- ment manufacturers are be- ginning to respond to the needs of the laboratory tech- nician with commercial SFE systems.

Hewlett-Packard Co., Avondale, PA, and Suprex Corp., Pittsburgh, have SFE units that retail for about $30,000. Computer Chemi- cal Systems Inc., Avondale, PA, has models starting at $15,000. Isco Inc., Lincoln, NE, began shipping its first $15,500 SFE instruments last November, and Dionex Corp., Sunnyvale, CA, just introduced an SFE unit in January with a $29,500 price tag.

Specialty gas manufactur-

One EPA researcher wants the agency to reduce methylene chloride consump

ers have also responded to the needs of SFE in the laboratory, and are now developing a line of pre-purified car- bon dioxide products.

toxic solvent elimination, supercritical fluid extractors can process up to eight

In addition to the major be

the ability to conveniently add a co- solvent or modifier to the supercritical fluid on-line with a unique syringe pump style of delivery.

With the ability to precisely control the parameters of time, temperature, pressure, flow-rate, and modifier con- tent, the versatility of SFE is almost limitless.

In some instruments, the sample can be introduced via a portable con- tainer delivery system. Cartridges may be taken into the field, loaded with sample and transported back to the laboratory for sample extraction and analysis. Efforts are underway to offer disposable SampleFartridges for added convenience.

Since relatively large volumes -af a

For More Information 1 To receive additional information on commercially available SFE equip- ment, circle the appropriate numbers on the Reader Service Card. ,&

Space limitations preclude a'listing of all manufacturers of SFE systems and components. For this idorma- tion, see the R 6 D Magazine Product Source Guide under "Extraction, su- percritical fluid. "

Computer Chemical Systems 563 Dionex Corp. 564 Hewlett-Packard Co. 565 Isco Inc. 566 Suprex Corp. 567

sample matrix can be extracted, up to 50 ml of sample volume in some cases, acceptable sensitivities of less than 1 ppb have been achieved.

Ebmples of applications for SFE use include environmental analytes such as pollutants, PCBs, PAHs, and pesticides from soils, sediments, and sorbents. Polyethylene additives such as Tinuvin, Irganox, and Irgafos, as well as lubricants, mold release agents, and antistatic agents from pro- cessed polymers and fibers have been extracted. Even fragrances and surfac- tants in soaps and the active ingredi- ents in creams can be isolated.

But do these SFE benefits justify an expenditure of from $15,000 to $30,000? Let's look at the numbers. If we assume a savings of $2.90 per test, and an average workload of 150 extractions per week, a $15,000 in- strument would have a payback in

eight months. An expenditure of $30,000 could be repaid with savings in less than a year and a half, ignoring the financing costs involved.

What's down the road for SFE? The future growth in research and devel- opment appears to be wide open. And when the EPA mandates the elimina- tion of methylene chloride in the labo- ratory, together with the availabihty of convenient analytical instrumenta- tion and an unlimited supply of a safe, nontoxic, and inexpensive solvent, su- percritical fluid extraction should be- come very popular. R&D

READER RESPONSE PANEL Please rate your interest in this article by circling the appropriate number on the Reader Service Card. High 507 Medium 508 Low 509

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44 R&D Magazine, March 1991

Environmentally Safe Products, page 32

IN BRIEF 5 Argonne, Baxter combat viruses. EM waves help find tunnels. DOE to plug radioactive leaks.

13

17 ments continue growth in

20

STRY EVENTS 29

72

lution and the mixed reviews it is re- I . . o- ni ,. i. r . < 1

The International Magazine of Research and,Development I

Environmentally Safe Products: [t’s Not Easy Being Green 32 ;mart companies are realizing that to be succg+Fful in the 1990% rou must develop products with the environment in s“ mind.

SFE: Will It Solve Your Lab’s Solvent Waste Problems? 40 iupercritical fluid extraction, offers a nontotic alternative to monventional techniques. Will it work for you?

Shop Like a Pro For Your Image Analysis System 48 Zomputer image analysis systems are getting Here are today’s trends, plus a dozen shoppi

taminants N Shut Down Your Cryocooler 66