Evaluation of analytical methods for determining pesticides in baby foods and adult duplicate-diet samples

Determination of pesticides in food is often complicated by the presence of fats and requires multiple clean-up steps before analysis. Cost-effective methods are needed for analyzing the large number of samples generated in l arge-scale exposure studies. We examined two extraction methods, supercriti cal fluid extraction (SFE) and accelerated solvent extraction (ASE), couple d with various clean-up techniques for the analysis of pesticides in baby f oods and exposure samples. The SFE-gas chromatogram/mass spectrometry (GC/M S) method did not provide quantitative recoveries(< 50%) of the pesticides spiked into fatty baby foods. This led to the evaluation of ASE-enzyme-link ed immunosorbent assay (ELISA) and ASE-GC/MS. Two solvents (acetonitrile (A CN) and ethyl acetate), three extraction temperatures (80, 100, and 120 deg reesC), and several different sample clean-up procedures were evaluated. A set of ASE conditions was developed that consisted of extracting baby food with ACN at 80 degreesC under 2000 psi pressure. An ENVI-Carb solid phase e xtraction (SPE) condition was also developed to clean the ACN extract. The clean-up fraction was analyzed by ELISA for chlorpyrifos and by GC/MS for m alathion, chlorpyrifos, and 4,4' -DDT. Duplicate-diet samples were analyzed for target pesticides by ASE-ELISA and by ASE-GC/MS. Concentrations of the se compounds ranged from <0.3 to 110 ppb. (C) 2001 Elsevier Science B.V. Al l rights reserved.