Determination of paraquat residues in soil by an enzyme linked immunosorbent assay

Abstract

A rapid, convenient and accurate method, based upon an enzyme linked immunosorbent assay (ELISA), is described for the determination of paraquat residues in soil. Polystyrene plates, coated with paraquat-keyhole limpet haemocyanin (KLH) conjugate, are incubated with the test samples and a known amount of monoclonal antibody. Residual antibody that has not reacted with free paraquat in the sample combines with paraquat-KLH on the plate. The determination of the fixed antibody is achieved by the addition of peroxidase labelled rabbit anti-mouse immunoglobulin G followed by reaction with a chromogenic substrate. The enzyme activity of the solid phase is determined from the absorbance measurements, which are inversely proportional to the concentration of paraquat. The method shows high specificity and correlates well with the traditional ion exchange-spectrophotometric method for the determination of paraquat.