Development and validation of an ELISA for metolachlor mercapturate in urine Original Research Article

The National Institute for Occupational Safety and Health (NIOSH) has conducted an exposure assessment study of herbicide applicators exposed to numerous commercial acetanilide-containing products. An enzyme-linked immunosorbant assay (ELISA) was developed to measure the putative major human metabolite of one of these, metolachlor mercapturate (MM). Antibodies were obtained by immunizing rabbits with a keyhole limpet hemocyanin (KLH) MM conjugate and the sera used as a source of IgG antibodies for the ELISA development. The percent cross-reactivities for metolachlor (ME), acetochlor mercapturate (ACM), alachlor mercapturate (AM) and alachlor (AL) were 39 and 23, respectively. Cross-reactivity for alachlor mercapturate (AM) and alachlor (AL) are not given as 50% inhibition was not observed for the highest concentration tested. Percent inhibitions at 20 μg l−1 for MM, ME, ACM, AM and AL were 20, 29, 48, 72 and 90, respectively. The measured least detectable dose (LDD) of metolachlor mercapturate was 0.18 μg l−1. Inter-assay concordance was <15%. These data indicate that the MM ELISA developed in this study may be used to estimate body burdens of ME from urinary metabolites of herbicide applicators.