Evaluation of a Rapid Quantitative Organic Extraction System for Determining the Concentration of PCB in Soils

摘要

The ORNL Analytical Chemistry Division has evaluated a unique commercial organic extraction system as a possible alternative method to EPA 3540 and EPA 3550 (1), for the rapid quantitative extraction of PCB from soils and sediments. The extraction system, tradenamed SOXTEC System HT, has been evaluated to determine whether equivalent extraction efficiency to the EPA methods in SW 846 can be achieved with significant reductions in extraction time and cost per analysis. The SOXTEC extraction utilizes the SW 846 cellulose thimble and hexane-acetone extractant, and generally follows the 3540 methodology, with two significant differences. These two differences are in the initial extraction stage, when the specimen-loaded thimble is immersed directly into the hot solvent. This ensures very rapid and intimate contact between the solvent and the specimen, resulting in rapid extraction of the PCB. The thimble is then elevated above the solvent and rinse-extracted as in Method 3540. The second difference is in the final stage, when the solvent is evaporated directly from the SOXTEC collection vessels, as would occur in the K/D step of Method 3540. The extracted specimens are then ready for measurement of the PCB concentrations by the electron-capture GC Method 8080 in SW 846. The initial evaluation was to determine optimum extraction parameters, using spikes of the 1254 and 1260 Aroclors in Fuller's earth. Our hypothesis was that extraction of dried PCB from the high porosity and surface area of the clay would be far more difficult than extraction of similar PCB Aroclors coated onto soil and mineral particles. This hypothesis was corrected, and illustrative data will be presented. (ERA citation 13:043566)