Correlation study of enzyme-linked immunosorbent assay and high-performance liquid chromatography/tandem mass spectrometry for the determination of N-methylcarbamate insecticides in baby food

In this work, a correlation study of monoclonal antibody-based enzyme-linked immunosorbent assays (ELISAs) and a liquid chromatography–electrospray mass spectrometric (HPLC/ESI/MS/MS) method for the determination of N-methylcarbamate insecticides carbofuran, carbaryl and methiocarb in fruit baby food is presented. The comparison of performance characteristics of the two methods was carried out by simultaneous analysis of apple–strawberry baby food (GPC purified) extracts spiked with N-methylcarbamates at six different concentration levels. Results obtained by ELISA correlated well with those obtained by LC/MS/MS, both in terms of trueness and precision. Recoveries, i.e. the ratio of the determined concentration to the known spiked concentration, were in the 60–100% range for ELISA and in the 73–104% range by LC/MS/MS with the RSDs from seven replicate analyses 3.6–23.3 and 1.7–8.2%, respectively. The influence of sample pre-treatment on the analytical performance of immunoassay method was also assessed. Using ELISA recoveries close to 90% were obtained even in crude non-purified baby food extracts. The limits of detection (LODs) by ELISA were 0.3, 0.04 and 0.02 g/kg−1 for carbofuran, carbaryl and methiocarb, respectively, whereas using LC/MS/MS 1 g/kg was the detection limit for all three insecticides. The results clearly indicate that the developed ELISA is suitable for the fast, quantitative and reliable determination of carbaryl, carbofuran and methiocarb in baby food even for the analysis of crude non-purified extracts. © 2003 Elsevier B.V. All rights reserved.