Stability of organochlorine and organophosphorus pesticides when extracted from solid matrixes with microwave energy

• Published in: Journal of AOAC International Vol. 81; no. 6
• Main Authors: Lopez-Avila, V. (Midwest Research Institute, California Operations, Mountain View, CA.), Benedicto, J, Bauer, K.M
• Format: Journal Article
• Language: English
• Published: 01.11.1998
• Subjects: ANALISIS DEL SUELO; ANALYSE DE SOL; CHEMICAL COMPOSITION; COMPOSE ORGANOCHLORE; COMPOSE ORGANOPHOSPHORE; COMPOSICION QUIMICA; COMPOSITION CHIMIQUE; COMPUESTO ORGANICO DEL CLORO; COMPUESTO ORGANICO DEL FOSFORO; DEGRADACION; DEGRADATION; DETERMINATION; ESTABILIDAD; EXTRACCION; EXTRACTION; MEASUREMENT; MEDICION; MESURE; MICROWAVE TREATMENT; MICROWAVE-ASSISTED EXTRACTION; ORGANOCHLORINE COMPOUNDS; ORGANOPHOSPHORUS COMPOUNDS; PESTICIDE; PESTICIDES; PLAGUICIDAS; SOIL TESTING; STABILITE; STABILITY; TRAITEMENT AUX MICROONDES; TRATAMIENTO POR MICROONDAS
• ISSN: 1060-3271; 1944-7922
• DOI: 10.1093/jaoac/81.6.1224

A stability study of 44 organochlorine pesticides (OCPs) and 47 organophosphorus pesticides (OPPs) was conducted. Compounds were spiked into solvent only (hexane-acetone, 1 + 1; methylene chloride-acetone, 1 + 1; methyl tert-butyl ether [MTBE]; and toluene-methanol, 10 + 1), solvent/dry soil suspensions, and solvent/wet soil suspensions (20% water, w/w). Spiked matrixes were heated in closed vessels with microwave energy at 2 temperatures (50 degrees and 145 degree C) for 5 or 20 min. For comparison and for determination of nitrogen blowdown losses, spiked matrixes that had not been exposed to microwave energy were concentrated by using the blowdown technique and analyzed for each of the spiked compounds. For OCPs, temperature had the most significant effect on compound recovery, followed by matrix. All 3 pairwise comparisons of the 3 matrix types were statistically significant. The solvent factor was also significant, with average recoveries of 97.8% with methylene chloride-acetone, 96.3% with toluene-methanol, 92.8% with hexane-acetone, and 92.3% with MTBE. Of the 6 pairwise comparisons among the 4 solvents, all but 2--methylene chloride-acetone versus toluene-methanol and hexane acetone versus MTBE--were statistically significant. For OPPs, temperature also had the most significant effect on recovery, followed by matrix. All 3 pairwise comparisons of the 3 matrix types were statistically significant in the same order as for OCPs. The solvent factor was also significant, but average recoveries--89.5% with hexane acetone, 89.4% with methylene chloride acetone, and 81.5% with either MTBE or toluene-methanol--are in a slightly different order from that for OCPs. Of the 6 pairwise comparisons among the 4 solvents, all but 2--hexane acetone versus methylene chloride-acetone and MTBE versus toluene-methanol--were statistically significant. Compounds that appear to degrade under microwave-assisted extraction conditions include TEPP, phosphamidon, trichlorfon, naled, mono...