Immunoaffinity purification of chlorimuron-ethyl from soil extracts prior to quantitation by enzyme-linked...

A competitive-indirect enzyme-linked immunosorbent assay (CI-ELISA) was developed to quantify chlorimuron-ethyl in soil. The linear working range of the assay was from 1 to 1000 ng mL(-)(1). The assay had an I(50) value of 54 ng mL(-)(1), with a limit of detection of 2 ng mL(-)(1) and a limit of quantification of 27 ng mL(-)(1). Three soils were extracted using a carbonate buffer (pH 9.0) and the extracts spiked with chlorimuron-ethyl. Because of the effects of coextractants (matrix effects) from soil on the accuracy and precision of the ELISA, immunoaffinity chromatography (IAC) was used to purify chlorimuron-ethyl from soil extracts prior to analysis. The immunoaffinity columns, which had a total binding capacity of 1350 ng of chlorimuron-ethyl mL(-)(1) of immunosorbent, were prepared by binding anti-chlorimuron-ethyl antibodies to protein G Sepharose 4B. Although the matrix effects were largely removed using the affinity column, they could be completely removed by first passing the extract through a column containing epoxy-coupled 1,6-diaminohexane (EAH) Sepharose 4B to remove organic acids prior to IAC. Assay sensitivity was increased 100-fold using IAC to purify and simultaneously concentrate chlorimuron-ethyl from soil extracts. The purification strategy (EAH followed by IAC chromatography) removed matrix effects from all three soils and allowed for the accurate quantitation of chlorimuron-ethyl in soil extracts.