Development of an enzyme-linked immunosorbent assay for 3,5,6-trichloro-2-pyridinol .2. Assay optimization and application to environmental water samples

A monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA) for 3,5,6-trichloro-2-pyridinol (TCP), the major degradation product of chlorpyrifos, chlorpyrifos-methyl, and triclopyr pesticides, was optimized for the analysis of this hydrophilic compound in water. A direct ELISA format was chosen, and the concentration of immunoreagents was first selected to provide the highest sensitivity. Next, the influence of several physical (temperature, time) and chemical (pH, salt, detergent) conditions was studied. Under optimized conditions, the TCP concentration giving 50% reduction of the maximum ELISA signal (I-50) in the competitive standard curve was 0.62 nM (0.12 mu g/L), and the assay was very specific for TCP. Preliminary evaluation of assay performance in water samples showed the absence of significant matrix effects for the waters tested, whenever the ionic strength of samples was approximately adjusted to that of standards. The assay provides a limit of detection of 0.04 mu g/L and a working range of 0.09-0.91 mu g/L TCP and allows for a precise and accurate determination of this pesticide degradation product in water at levels as low as 0.1 mu g/L without sample cleanup.