Application of Immunoassays to Studies of the Environmental Fate of Endosulfan

Abstract

A comprehensive validation of three endosulfan immunoassays (two microwell assays and a tube assay) using field samples was conducted as part of a study on the environmental fate of endosulfan applied to Australian cotton fields. The validation included an initial examination of the relationship between tube and microwell immunoassays and then correlations between immunoassay data and gas−liquid chromatography (GLC) analyses for several thousand water (in a format with a detection limit of 0.2 μg L-1) and soil samples and hundreds of aerial drift samples. In all cases, the immunoassay data proved to be closely correlated with GLC analyses, indicating that these immunoassays provide a reliable quantification of endosulfan. Validation of immunoassay methods against GLC by providing reliable correlations was an important result, but in this study immunoassay also was useful in the research program for improving protocols for sampling and analysis by GLC. This was possible because of the demonstrated advantages of immunoassay for greater speed and higher sample throughput with less complicated sample preparation, which allows many more samples to be analyzed and a more comprehensive study of field processes such as rain simulation. The ability of immunoassay to provide a summation of the three toxic forms of endosulfan (α, β, and sulfate) was exploited. It is concluded that this immunoassay for endosulfan is quantitative using soil, water, and aerial drift samples and that it would allow the possibility of decision making at field sites, improving environmental management of endosulfan residues. Keywords: Immunoassay; endosulfan; gas chromatography; application; dissipation studies; soil; water; drift