COMPARISON OF SUPERCRITICAL FLUID EXTRACTION WITH CLASSICAL SONICATION AND SOXHLET EXTRACTIONS FOR SELECTED PESTICIDES

The supercritical fluid extraction of organophosphate and organochlorine pesticides from soils was investigated and compared to the classical sonication and soxhlet extractions. Four soils, sand, clay, top soil, and river sediment, were spiked with 12 organochlorine and organophosphate pesticides. These soils were extracted with supercritical CO2 modified with 3 % MeOH at a pressure of 350 atm and a temperature of 50-degrees-C. Overall average recoveries of the 12 pesticides were greater than 85 % for each of the soil matrices, and the overall average relative standard deviation (RSD) for all the pesticides and soils was 5.1 %. Secondly, a large batch of top soil was specially prepared and fortified with the same pesticides and repetively extracted using SFE (n = 9) and the classical sonication (n = 9) and soxhlet (n = 8) extractions. The recovery data and precision of each extraction method was evaluated statistically. It was found that overall average recoveries of the 12 pesticide compounds for the sonication, soxhlet, and supercritical fluid extractions were 94.7 %, 93.1 %, and 91.6 %, respectively. SFE demonstrated the best precision of the three extraction methods with the overall average relative standard deviation being 2.94 %. Lastly, native soils contaminated with organochlorine pesticides were repetitively extracted using SFE and the sonication extraction. Comparable precisions between SFE and the sonication method were demonstrated. Also SFE performed equally as well as the sonication extraction in recovering a number of organochlorine pesticides from the native soil samples.