Evaluation of Soxtec Extraction Procedure for Extracting Organic Compounds from Soils and Sediments

Abstract

Abstract A study was carried out to evaluate the Soxtec extraction of 29 target compounds (7 nitroaromatic compounds, 3 haloethers, 7 chlorinated hydrocarbons, and 12 organochlorine pesticides) from spiked sandy clay loam and clay loam. The study also compared 2 solvent mixtures (hexane–acetone (1 + 1) and methylene chloride–acetone (1 + 1)) and investigated the effect on method recovery of 5 factors (matrix type, spike level, anhydrous sodium sulfate addition, total extraction time, and immersion/ extraction time ratio), their 2-way interactions, and a 3-way interaction (matrix × spike × time). Of the 5 factors investigated, matrix type, spike level, and total extraction time had a significant effect on method performance at the 5% significance level for 16 of the 29 target compounds (4 compounds were not recovered at all, and analysis of variance was not significant at the 5% significance level for 9 compounds). Anhydrous sodium sulfate addition and immersion/extraction time ratio had insignificant effects for all but one of the target compounds. This effect may have been a random occurrence. The data indicate that the 2 solvents performed equally well and 4 compounds were not recovered at all. These 4 compounds were apparently lost from the spiked matrix. Experiments were performed to determine compound recovery at each step in the extraction procedure. Limited experimental work was performed with 64 basic/neutral/acidic compounds spiked onto clay loam and with 3 standard reference materials certified for polynuclear aromatic hydrocarbons. From the 64 compounds spiked onto clay loam at 6 mg/kg, 20 had recoveries of greater than 75%, 22 had recoveries from 50 to 74%, 12 had recoveries from 25 to 49%, and 10 had recoveries of less than 25%.