Complementation of GC-AED and ELISA for the Determination of Diazinon and Chlorpyrifos in Fruits and Vegetables

Abstract

Enzyme-linked immunosorbent assay (ELISA) was employed to screen produce samples for diazinon and chlorpyrifos levels. All positive samples were analyzed for these organophosphate insecticides with a newly developed gas chromatographic atomic emission detection (GC-AED) method. Produce was extracted in methanol by Polytron homogenization and cleaned up and concentrated using Sep-Pak C18 cartridges. Fortification and reproducibility studies were performed using apples, blueberries, green beans, lettuce, and tomatoes that were free of detectable levels diazinon and chlorpyrifos. Percent coefficient of variation (%CV) from the reproducibility studies ranged from 1.9 to 17 for chlorpyrifos and 1.9 to 11 for diazinon. Spiking studies demonstrated percent recoveries of 78 to 114% (%CV 3.1 to 13%) for diazinon and 82 to 123 (%CV 1.5 to 12) for chlorpyrifos. Of the 278 fruit and vegetable samples screened for both organophosphate insecticides, 59 were found to have detectable levels of diazinon and 35 samples were found to contain detectable amounts of chlorpyrifos. A correlation study between ELISA and GC-AED demonstrated that the correlation coefficient was 0.987 for diazinon and 0.967 for chlorpyrifos.