Determination of metolachlor in water and soil by a rapid magnetic particle-based ELISA

A competitive enzyme-linked immunosorbent assay (ELISA) for the quantitation of metolachlor in water and soil was developed using a magnetic particle-based solid phase. Metolachlor was covalently attached to bovine serum albumin carrier through the chloroacetamide moiety and the resulting herbicide-protein immunogen used in rabbits to produce polyclonal antibodies specific for metolachlor. The polyclonal antibodies are covalently attached to amine-terminated superparamagnetic particles and used as the solid phase in a rapid and sensitive immunoassay. This ELISA has a limit of detection of 0.05 ppb (parts per billion, nanograms per milliliter) in water and 3.0 ppb in soil. The ELISA compares favorably with GC measurements when water samples are analyzed (r = 0.976). Recoveries from fortified soils averaged 83% and 90% using 30-min and 24-h extractions with methanol/water (75:25 v/v), respectively