DEVELOPMENT OF A SUPERCRITICAL-FLUID EXTRACTION METHOD FOR PCBS AND CHLOROBENZENES FROM SOILS AND SLUDGE-AMENDED SOILS

The use of supercritical fluid extraction (SFE) with carbon dioxide to extract a range of PCB congeners and chlorobenzenes from soils and sl udge amended soils has been investigated. The system was operated unde r conditions of constant pressure providing a fixed extraction volume. Extraction variables studied included; CO2 pressure, extraction tempe rature, and presence of methanol as an organic modifier. Nearly quanti tative recoveries of the PCBs were achieved using a variety of extract ion conditions. The recoveries of the chlorobenzenes were lower and th is was probably directly related to their higher volatility resulting in evaporative losses whilst trapping the compounds in the collection solvent. Modification of the trapping system could overcome this limit ation. SFE offers both time savings and a reduction in solvent usage c ompared to traditional extraction methods e.g. Soxhlet.