Quantification of alachlor in water by a novel magnetic particle-based ELISA

An enzyme-linked immunosorbent assay (ELISA) was developed for determination of the weedkiller, alachlor, in water, using a magnetic-particle solid phase. The water sample and alachlor labelled with horseradish peroxidase (HRP) were incubated for 30 minutes with the antibody-coupled solid phase, and a magnetic field was then applied to the solid phase to remove unbound HRP-alachlor and any interfering substances. The enzyme substrate (hydrogen peroxide) and a chromogen (3,3',5,5'-tetramethylbenzidine) were then added and incubated for 20 minutes. Acid was added to stop the reaction, and the coloured product was measured with a specially-designed, microprocessor-controlled photometer. Results from validation of the method on samples of groundwater are presented.