SCIENCE & TECHNOLOGY
PUTTING SAFETY FIRST Accidents spark some researchers to switch to safer method of purifying organic solvents
switched four of the most popular solvents in his lab to the new systems. But even though the column-absorption systems clearly win the safety debate, not everyone has made the switch. Researchers at some colleges and universities, as well as some smaller chemical and pharmaceutical companies, have stuck with conventional solvent stills.
The dangers of the conventional chemistry professor William J. method for solvent purification spurred Evans at the University of Cali- chemistry professor Robert H. Grubbs of fornia, Irvine, caused $3.5 million California Institute of Technology to seek ONE BIG REASON is price. Researchers in damage and seriously burned a an alternative. In collaboration with Dow, must pony up approximately $4,000 to graduate student. The student was per- Grubbs published a method relying on ac- $5,000 per solvent to replace their stills forming a task that he had done hundreds tivated alumina and a copper catalyst to with the commercial systems. And alof times before—purifying an organic sol- remove moisture and oxygen from organ- though hundreds of liters of solvent can be purified per column, replacing the packvent using a reflux/distillation apparatus, or ic solvents [Organometallics, 15,1518 (1996)}. solvent still—when hot benzene escaped A number of firms, including Granada ing costs about $200 per column. "Monfrom the apparatus and ignited. Hills, Calif-based Anhydrous Engineering ey is the deciding factor for departments Although it may have been the most and Newburyport, Mass.-based Innova- making these decisions," Grubbs says. Despite the hefty price tag, replacing costly, the UC Irvine fire was not the first tive Technologies, now offer systems based solvent stills may save money over the long accident involving organic solvent purifi- on Grubbs's method. cation; many researchers have experienced Although the dangers of handling flam- term by cutting waste and energy confires, floods, or spills. "The potential for mable solvents remain, these safer systems sumption, according to a recent study at major disaster with solvent stills is quite operate at ambient temperatures and don't the University of Wisconsin, Madison. Unlike solvent stills, the new large," says Steven W Baldwin, systems don't need to be placed an organic chemistry professor inside safety hoods, which are at Duke University "I think we're costly to operate. operating on borrowed time." Wisconsin's chemistry deMany organic and organopartment built its own systems metallic reactions require solat a fraction of the cost of those vents that are free of water and, commercially available. Sharing sometimes, free ofoxygen. Clasthe systems could also defray sically, solvent purification is their cost. accomplished by refluxing the solvent in the presence of sodiBut should safety concerns um or potassium metal and outweigh the costs? "Since benzophenone in an inert atthere is a safer solution availmosphere. The reactive metal able, when there is a problem, removes moisture from the solthe university really opens itself vent, and the ketyl intermediate up to liability," Baldwin argues. that forms upon reaction of the SAFER Duke University graduate student Wayne Yount "Institutions should provide ketone and the metal helps to sop draws solvent from purification column. both a mandate and incentive" up any oxygen. The blue color of to make the switch, he says. benzophenone ketyl is used as an indicator require reactive metals. Instead, dry niFunding safety measures at universities that the solvent is ready for use. trogen or argon is used to force solvent has always been contentious. "Ideally, safeSome labs commonly require several over columns containing moisture-scav- ty is part of the infrastructure of doing liters of each of four or five different wa- enging activated alumina and oxygen-scav- business in the institution," says Stanley ter- and oxygen-free solvents per day To enging copper catalyst. Columns can be H. Pine, a professor emeritus of chemistry meet demand, many liters of each solvent scaled up or down as needed, but each must at California State University, Los Angeare allowed to reflux for long periods of be dedicated to a single solvent. A few sol- les, and a member ofthe investigation team vents —ether, tetrahydrofuran, and meth- for the UC Irvine fire. 'And, therefore, it time, much of it unattended. Having large quantities of flammable ylene chloride—are compatible with acti- should come from the top." Pine suggests solvent around the lab is a safety concern vated alumina but not with the copper that the university administration, the in and of itself, but dangers inherent in the catalyst. Oxygen must be removed from chemistry department, and individual rereflux/distillation solvent purification these solvents by purging them with dry searchers should share fiscal responsibility for the new systems. process exacerbate the hazard. The setup nitrogen or argon. The potential for serious injury and exrequires electrical equipment such as a The potential for accidents like the one heating mantle and a vacuum pump—ei- at UC Irvine has pushed many big univer- pensive damage demands researchers sether of which can create a spark. In addisities and companies to abandon solvent riously consider switching to the new systion, if even a small piece of reactive met- stills. The alternative systems are ubiqui- tems, Baldwin says. 'A single disaster would al escapes during purification or cleanup, tous at Massachusetts Institute of Tech- cost infinitely more than replacing the stills the moisture in the air can be sufficient to nology and Caltech. At the time of the ac- with what is now available."—AMANDA cident at UC Irvine, Evans had already YARNELL ignite the metal.
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