THE USE OF SUPERCRITICAL-FLUID EXTRACTION IN ENVIRONMENTAL-ANALYSIS

Different applications of supercritical-fluid extractions (SFE) in the field of environmental trace analysis are presented. A simple method for quantitative trapping of extracted compounds in off-line SFE is described in detail. With this device, compounds with a boiling point higher than 120-degrees-C could be trapped with recoveries of over 90% compared with external standard. Recovery studies of chlorinated pesticides (Lindane and pp'-DDT) and polychlorinated biphenyls (PCB's) in soil were performed at low ppb levels. On-line SFE-GC was used to measure the recoveries of PCB's from the adsorbents Tenax, Carbopack C, Spherosil XOA 200, Florisil and reversed phase C18 sorbent. It was shown that the adsorbents gave satisfactory blanks with SFE cleaning. Ten-minute extractions yielded quantitative recoveries (500 pg) of the PCB's. Carbopack cannot be used under supercritical conditions due to the instability of the material. High molecular artefacts were observed, when large volume of air was enriched on Tenax. A low volume sampling/SFE-unit for the analysis of aerosol particles is presented and aspects of fractionation of particulate organic matter and selective extraction of PAH's by stepwise SFE are discussed.