ity Assurance Program; and Joan Barnes, also of the Office of Solid Waste, presented an overview of the Superfund Analytical Services Program. During the remainder of the symposium, researchers from EPA, academia, and industry made presentations aimed at helping practicing environmental analysts solve problems encountered in their work. New sample preparation methods such as microwave digestion and supercritical fluid extraction (SFE) are joining the triedand-true standard digestion and extraction methods, and new instrumental methods such as ICP/MS, LC/MS, and SFC are being used more frequently to complement the traditional LC, GC, and GC/MS methods. Microwave digestion and SFE are advantageous for sample preparation in elemental and organic analysis, respectively. According to David Binstock of the Research Triangle Institute (Research Triangle Park, NC), techniques typically used for preparation of samples for trace elemental analysis are time-consuming and often involve the use of acid digestions and thermal decompositions that may lead to analyte losses, incomplete recoveries, or sample contamination. Microwave digestion, however, can result in significantly reduced preparation time without deterioration of either accuracy or precision. The increased use of supercritical fluids (SFs) for sample extraction is based on a combination of the properties of SFs and the increased availability of both off- and on-line equipment for SFE, said Viorica Lopez-Avila of Acurex Corp. (Mountain View, CA). Because the high-solute diffusivities of SFs compared with conventional solvents provide much higher extraction efficiencies, extraction conditions can be adjusted so that compounds can be separated according to their volatility and polarity. Very little organic solvent is needed for collection of extracted materials, and the SF can be completely separated from the extracted material in the release step by reducing the pressure to ambient pressure. A study of supercritical extraction of EPA priority pollutants from various matrices (i.e., sand, urban dust, coal, coal fly ash, and soil) indicates that SFE has the potential to be a useful technique for the environmental chemist. Several speakers discussed the use of inductively coupled plasma mass spectrometry (ICP/MS) for the determination of trace elements in water and solid waste. According to Thomas Hinners of the EPA Environmental Monitoring Systems Laboratory (Las
Vegas, NV), ICP/MS offers detection limits below a part per billion for multielement analysis with the convenience and speed of nebulizer sample introduction. An interlaboratory study comparing the analysis of nearly 36,000 water, fly ash, sediment, industrial sludge, and soil samples by atomic absorption spectroscopy, ICP-atomic emission spectroscopy (ICP-AES), and ICP/MS showed that analytical precision is more variable with ICP/MS than with ICP-AES for several elements, possibly because of the additional dilutions necessary for ICP/MS analysis. Preliminary results indicate that ICP/MS is suitable for determination of many elements, but they do not support using ICP/MS to determine potassium, selenium, silver, sodium, and vanadium in solid waste. For the determination of organics, LC/MS is becoming more popular because of its ability to separate and quantitate nonvolatile or thermally labile compounds that are not amenable to GC or GC/MS. LC/MS methods using both thermospray and the new particle beam LC/MS technology to characterize dyes, chlorinated herbicides and esters, carbamate pesticides, and other environmentally important compounds were described. As indicated by the symposium's title, a large part of the meeting was devoted to quality assurance and quality control issues, including the definition and classification of hazardous waste matrices, determination of detection limits, laboratory accreditation and audits, quality control in field sampling, multivariate analysis of QA/QC data, interlaboratory quality assurance, and the use of laboratory automation and laboratory information management systems. Finally, various field methods and sampling protocols, including several portable instruments for on-site determination of pollutants, were described. For example, Albert Robbat and George Xyrafas of Tufts University described a fieldable GC/MS for identification and quantitation of PCBs; and Marcus Wise, Michael Gurein, and Michelle Buchanan of Oak Ridge National Laboratory described a direct-sampling ion trap mass spectrometer that can be used for the rapid determination of volatile organics in water, soil, and air. Next year's symposium will again be held in Washington, DC, July 16-20, 1990, and promises to be even better than this year's, with stimulating technical presentations and the second annual EnvirACS Exposition. Sharon Boots Mary Warner
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ANALYTICAL CHEMISTRY, VOL. 61, NO. 18, SEPTEMBER 15, 1989 · 1049 A
