Development of a sensitivity enhanced multiplexed fluorescence covalent microbead immunosorbent assay (FCMIA) for the measurement of glyphosate, atrazine and metolachlor mercapturate in water and urine

Body burdens from exposures to pesticides may be estimated from urinary analyses of pesticide parent/metabolite concentrations. Pesticide applicators and others are often exposed to numerous unrelated pesticides, either sequentially or simultaneously. Classically, body burdens of pesticides are analyzed using chemical/instrumental analysis (CIM) or enzyme immunoassays (EIAs). Both of these technologies can usually be used to quantitate one analyte (or closely related groups of analytes) per analysis. Alternatively, multiple analytes can be measured simultaneously using a multiplexed fluorescence covalent microbead immunoassay (FCMIA). We developed a multiplexed FCMIA to simultaneously measure glyphosate (Gly), atrazine (Atz), and metolachlor mercapturate (MM) in water and urine. The assay had least detectable doses (LDDs) in water/diluted urine of 0.11/0.09 ng/ml (Gly, water/urine LDD), 0.10/0.07 ng/ml (Atz) and 0.09/0.03 ng/ml (MM). The sensitivity for the measurement of Gly was enhanced by derivatization. All assays gave linear responses from the LDDs for each respective pesticide to 300 ng/ml. There was no cross-reactivity between the three analytes. Using a 96-well microplate and an autosampler, as many as 288 separate analyses can be completed in approximately 120 min with precision, sensitivity, and specificity equivalent to, if not better, than that found when these same analytes are measured by CIM or EIA.