Determination of chlorpyrifos in fruits and vegetables by ELISA and confirmation by GC-AED

A commercial polyclonal plate ELISA was validated for the analysis of chlorpyrifos in fruits and vegetables. Produce was extracted by high speed homogenization IO g of a homogeneous subsample in 20 mi of methanol for 3 min followed by clean-up with C-18 Sep-Paks. All samples and standards were analyzed in 10% final methanol concentration. Reproducibility studies yielded per cent coefficients of variation (%CVs) from 2.1 to 20. Fruits and vegetables fortified at five different levels demonstrated percent recoveries ranging from 77 to 92 (%CVs of 4.0 to 14) for chlorpyrifos. A comparison of the analysis of 35 positive chlorpyrifos samples between ELISA and a gas chromatography-atomic emission detector method indicated good agreement with a correlation coefficient of 0.967 and a slope of 0.9583.