Validation of a monoclonal enzyme immunoassay for the determination of carbofuran in fruits and vegetables

The N-methylcarbamate pesticide carbofuran is a very important insecticide used worldwide. In the present work, the validation of a monoclonal antibod y-based enzyme immunoassay (ELISA) to determine this compound in fruits and vegetables is described. The immunoassay is a competitive heterologous ELI SA in the antibody-coated format, with an I-50 value for standards in buffe r of 740 ng/L and with a dynamic range between 200 and 3100 ng/L. For recov ery studies, peppers, cucumbers, strawberries, tomatoes, potatoes, oranges, and apples were spiked with carbofuran at 10, 50, and 200 ppb. After liqui d extraction, analyses were performed by ELISA on extracts purified on soli d-phase extraction (SPE) columns and crude, nonpurified extracts. Depending on the crop, mean recoveries in the 43.9-90.7% range were obtained for pur ified samples and in the 90.1-121.6% range for crude extracts. The carbofur an immunoassay performance was further validated with respect to high-perfo rmance liquid chromatography (HPLC) with postcolumn derivatization and fluo rescence detection (EPA Method 531.1). Samples were spiked with carbofuran at several concentrations and analyzed as blind samples by ELISA and HPLC a fter SPE cleanup. The correlation between methods was very good (y, = 0.90x + 2.66, r(2) = 0.958, n. = 25), with HPLC being more precise than ELISA (m ean coefficients of variation of 4.1 and 11.5%, respectively). The immunoas say was then applied to the analysis of nonpurified extracts of the same sa mples. Results also compared very well with those obtained by HPLC on purif ied samples (y = 1.02x + 10.44, r(2) = 0.933, n. = 29). Therefore, the deve loped immunoassay is a suitable method for the quantitative and reliable de termination of carbofuran in fruits and vegetables even without sample clea nup, which saves time and money and considerably increases the sample throu ghput.