Evaluation of a Commercially Available Enzyme‐Linked Immunosorbent Assay and a Liquid Chromatography–Tandem Mass Spectrometric Method for the Analysis of Glyphosate in Wheat, Oats, Barley, Malt, and Lentils

Abstract

An accurate and precise ultra‐high performance liquid chromatography with tandem mass spectrometry (UHPLC‐MS/MS) method was validated for the analysis of glyphosate and its main transformation product (aminomethylphosphonic acid) in barley, malt, wheat, oats, and lentils. The validation data demonstrated good performance of the method. This UHPLC‐MS/MS method was also used to evaluate the performance of a commercially available enzyme‐linked immunosorbent assay (ELISA) test kit. For all of the grain matrices examined, the ELISA showed poor accuracy and precision at its stated lower working limit of 0.075 mg/kg; however, performance was acceptable at 0.30 mg/kg, as well as higher concentrations relevant to established maximum residue limits. At these relevant concentrations, the ELISA also produced results higher than the UHPLC‐MS/MS method. Although results from the two methods were linearly correlated, differences in the result values from the two methods differed among the grains studied and ranged from +1% for oats to +40% for glyphosate concentrations in barley. ELISA is a useful tool that is complemented by the comprehensive and sensitive UHPLC‐MS/MS method.