Submitted to: Journal of Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 8, 1999
Publication Date: N/A
Interpretive Summary: Extraction is often the most time consuming step in pesticide residue analysis. Exhaustive methods such as Soxhlet extraction require the use of long time cycles (8-24 hours). Alternative methods such as solvent-shake extraction are highly labor intensive because of the use of multiple extraction steps. The sample throughput of these methods is typically low, and the cost is high because of the requirement for intensive human handling. In addition, large amounts of solvents are often needed, and their purchase and waste disposal further add to the overall cost of sample analysis. In recent years, several new extraction techniques have appeared, one of which is accelerated solvent extraction, or ASE. ASE extraction is done with a small amount of solvent (<50 mL) and in a very short time (<20 min). The efficiency of ASE for extracting pesticide residues form soil has not been adequately evaluated. In this study, we optimized ASE conditions for extracting two of the most used herbicides, atrazine and alachlor, and compared ASE with Soxhlet and solvent- shake extractions. The efficiency of ASE was generally better than that for Soxhlet or shake extraction using methanol-water (4:1, v/v). ASE extraction also consumed considerably less solvent than the other two conventional methods.
Technical Abstract: Accelerated solvent extraction, or ASE, is a new extraction technique that is similar in principle to Soxhlet extraction, but the use of elevated temperature and pressure with ASE allows the extraction to be completed within a short time and with a small quantity of solvent. In this study, we investigated the effect of residue aging, solvent type, and ASE conditions on the recovery of atrazine and alachlor from different soils, and compared the efficiency of ASE with that of Soxhlet and solvent- shake extractions. With ASE, the use of dichloromethane-acetone (1:1, v/v) or methanol as solvent resulted in significantly greater pesticide recovery than hexane. After the residue was aged for >2 weeks, pesticide recovery was significantly influenced by the extraction temperature in ASE vessel, and the recovery increased to 130-140oC and then decreased. The efficiency of ASE was generally better than that for Soxhlet or shake extraction using methanol-water (4:1, v/v). ASE extraction also consumed considerably less solvent than the other two conventional methods.