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Analytical chemistry.

Plasma Spectrometer Simplifies Trace Analysis

While plasma ionization and ion-trap mass spectrometry have been available for several years, a novel instrument developed by a research team at DOE's Pacific Northwest National Laboratory (PNNL), Richland, Wash., and Finnigan Corp., San Jose, Calif., consolidates the two technologies.

The Plasma Source Quistor (PSQ), which possesses both on-line and real-time chemistry capabilities, was developed for analyzing trace-element contamination, radioactive-waste disposal, and industrial-pollution cleanup. Its principal applications so far have been the determination of actinide isotopes in support of nuclear-proliferation monitoring and the determination of trace elements in semiconductor processes.

The PSQ frees users from troublesome interference problems and ion-repulsion effects.

The PNNL team: David Koppenaal, Charles Barinaga, and Gregory Eiden. Also on the team: Charles Douthitt of Finnigan.

Correcting for Specie Changes

Accurate bulk measurements of samples' elemental composition have become routine. These same techniques, however, don't work for many elements and molecules that react differently in various specie forms.

Until now, only a final concentration could determine an accurate measurement. But with Speciated Isotope Dilution (SID) Mass Spectrometry, developed by Skip Kingston of Duquesne University, Pittsburgh, researchers now have a tool that corrects for the conversion of one specie to another in environmental, biological, pharmaceutical, and industrial samples.

SID does this by spiking the sample with one or more separated isotopes that have been chemically converted to a single specie, equilibrated with the naturally occurring specie, and extracted from the sample with the specie of interest.

Discharge Detector Eliminates Radiation Source

All electron capture detectors (ECDs) such as those used in gas chromatography use a radioactive foil as their ionization source. Changing regulations regarding transfer and disposal of radioactive materials, however, have made such detectors prohibitively expensive - and in some countries even illegal.

An alternative is the Pulsed Discharge Electron Capture Detector (PCECD), developed by Stanley Stearns of Valco Instruments, Houston, and Wayne Wentworth of the Univ. of Houston.

The PCECD is a pulsed discharge helium photoionization detector, easily configured to work as an ECD. It is compact and easily installed on existing instrumentation. Elimination of radiation is achieved with no negative trade-offs - in fact, sensitivity, stability, and reproducibility are reportedly 5 to 10 times better than with radioactive ECDs.

Rad Disks Simplify Sample Prep

The yearly cost of radiochemical analyses involved in decontaminating Dept. of Energy sites now exceeds $300 million. To reduce these costs, researchers at DOE's Argonne (Ill.) National Laboratory, 3M, St. Paul, Minn., and IBC Advanced Technologies, American Fork, Utah, have jointly developed a simpler, more cost-effective way to analyze these radionuclides.

The result is Empore Rad Disks for the selective adsorption of radioisotopes in aqueous samples. Measuring 47 mm in diameter and only 500 [[micro]meter] in thickness, Empore Rad Disks fit into existing instrumentation. They are made of polytetrafluoroetnylene fibrils (about 10%) embedded with densely packed AnaLig particles (about 90%).

Sorption of target radioisotopes is very efficient: They are concentrated close to the surface of the disk, while nontarget radioisotopes simply pass through and remain in the flitrate.

Micro-GC Measures Multiple Pollutants

When existing instrumentation couldn't precisely measure fluctuating concentrations of volatile organic compounds (VOCs) and hazardous air pollutants (HAPs) at RJ Reynolds Tobacco Co.'s packaging division, Winston-Salem, N.C., researchers looked into developing a new environmental device.

The resulting Xenith 9000 GQA Gas Quanitification Analyzer uses gas chromatography to continuously separate, speciate, and quantify most pollutants at selected emission points. It works by diverting a small part of the gas stream into a heated sample line that's routed to an analyzer maintaining wetted components at 120 [degrees] C. A special valve sends the gas stream through a micro-GC small enough that as many as eight complete systems can fit in a standard-size cabinet.

With this multiple processing capability, the GQA, available commercially through Servomex, Norwood, Mass., can simultaneously analyze as many as 50 compounds in under 5 min - up to three times the number of other instruments.

Extractor Boosts Sample Prep

A fully automated sample-extraction system developed by a 13-member research team at Dionex, Salt Lake City and Sunnyvale, Calif., uses solvents at high temperatures and pressures to rapidly remove analytes from solid or semisolid matrices.

The ASE 200 Accelerated Solvent Extractor has substantially improved solvent use and extraction time compared to other sample-prep devices. Elevated temperatures and pressures let extractions take place in about 15 min using 15 ml of solvent per 10-g sample, versus several hours and several hundred milliliters of solvent for conventional analysis.

Soxhlet extraction, the veteran standard for judging extraction, is not nearly as efficient. The ASE 200 uses about a tenth the solvent of Soxhlet and is about 30 times faster.
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Title Annotation:R&D Universe of Innovations
Publication:R & D
Date:Sep 1, 1996
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