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

A competitive-indirect enzyme-linked immunosorbent assay (CI-ELISA) was dev eloped to quantify chlorimuron-ethyl in soil. The linear working range of t he 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 quantific ation 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 eff ects of coextractants (matrix effects) from soil on the accuracy and precis ion of the ELISA, immunoaffinity chromatography (LAC) was used to purify ch lorimuron-ethyl from soil extracts prior to analysis. The immunoaffinity co lumns, which had a total binding capacity of 1350 ng of chlorimuron-ethyl m L(-1) of immunosorbent, were prepared by binding anti-chlorimuron-ethyl ant ibodies to protein G Sepharose 4B. Although the matrix effects were largely removed using the affinity column, they could be completely removed by fir st passing the extract through a column containing epoxy-coupled 1,6-diamin ohexane (EAH) Sepharose 4B to remove organic acids prior to IAC. Assay sens itivity was increased 100-fold using IAC to purify and simultaneously conce ntrate chlorimuron-ethyl from soil extracts, The purification strategy (EAH followed by IAC chromatography) removed matrix effects from all three;Soil s and allowed for the accurate quantitation of chlorimuron-ethyl in soil ex tracts.