Development of an immunochromatographic assay for the rapid detection of chlorpyrifos-methyl in water samples

A rapid (less than 10 min), qualitative and semi-quantitative immunochromatography using colloidal gold-antibody probe was successfully developed and applied in determination of chlorpyrifos-methyl (a wide-spectrum organophosphorus pesticide) in water samples. The qualitative detection limit of chlorpyrifos-methyl was determined as 0.6 μg ml(-1) by using immunochromatography. In the semi-quantitative experiment, the detection results of chlorpyrifos-methyl were scanned by a membrane strip reader, and a detection curve representing the scanned data average was obtained. After conversion, it was observed that in the range of 50-12,150 ng ml(-1), the graph between logit(B/B(0)) and logarithm of concentration of chlorpyrifos-methyl was linear, from which, the regression equation (y =-2.5229 x +7.5951, R(2)=0.9889) and IC(50) value (1024.39 ng ml(-1)) was obtained, respectively. Meanwhile, the detection limit was calculated as 132.91 ng ml(-1) by the extrapolation of B(0)-2SD. In addition, the cross-reactivities were less than 1% with tested analog compounds and regarded as negligible. The recoveries obtained by standard chlorpyrifos-methyl addition to water samples were 102.5-107.6%. Overall, to our knowledge, this is the first report of qualitative and semi-quantitative detection of chlorpyrifos-methyl by immunochromatography.