Development of an Enzyme-Linked Immunosorbent Assay for the Detection of Glyphosate

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Abstract
A competitive indirect enzyme-linked immunosorbent assay (CI-ELISA) was developed to quantitate the herbicide glyphosate [N-(phosphonomethyl)glycine] in water. The ELISA has a detection limit of 7.6 μg mL-1 and a linear working range of 10−1000 μg mL-1 with an IC50 value of 154 μg mL-1. The glyphosate polyclonal antisera did not cross-react with a number of other herbicides tested but did cross-react with the glyphosate metabolite aminomethylphosphonic acid and a structurally related herbicide, glyphosine [(N,N-bis(phosphonomethyl)glycine]. The assay was used to estimate, quantitatively with accuracy and precision, glyphosate concentrations in water samples. Water samples were analyzed directly, and no sample preparation was required. To improve detection limits, water samples were concentrated prior to analysis, resulting in the increase of the detection limits by 100-fold. After the sample preconcentration step, the detection limit improved to 0.076 μg mL-1 with an IC50 value of 1.54 μg mL-1, and a linear working range was 0.1−10 μg mL-1. Glyphosate concentrations determined by ELISA correlated well with those determined by high-pressure liquid chromatography (r2 = 0.99). This assay contributes to reducing the costs associated with conventional residue analysis techniques for the quantitation of glyphosate in water. Keywords: Glyphosate; ELISA; phosphonomethylglycine; AMPA; herbicide; residue; HPLC; postcolumn derivatization; analysis; immunoassay

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