DEVELOPMENT OF A MAGNETIC PARTICLE-BASED AUTOMATED CHEMILUMINESCENT IMMUNOASSAY FOR TRIASULFURON

A fully automated immunoassay with high sample throughput for the quantitative analysis of triasulfuron in soil has been developed. The competitive assay was run on the Ciba-Corning ACS: 180 benchtop immunoassay analyzer and used a combination of hapten-bound paramagnetic particles and acridinium ester-labeled monoclonal antibody. Different solid-phase antigens for assay optimization were compared. Three consisted of protein-hapten conjugates covalently linked to primary amine-coated particles, and one corresponded to the chloroethoxy phenylsulfonylurea moiety of triasulfuron with an extended aminopentyl spacer specially designed to improve assay sensitivity and to allow a single step coupling of the hapten to the particles without protein carrier. In the latter assay format, the limits of detection of triasulfuron were 0.02 mu g/L in aqueous media and 0.05 mu g/kg in soil. Specificity studies indicated that among several structurally related compounds, cinosulfuron showed 250% cross-reactivity while all other compounds studied showed <3.5%. Quantitative determinations of triasulfuron in soil samples obtained from a field trial were measured by automated immunoassay. They compared favorably with HPLC measurements (correlation coefficient of 0.96). The intra- and interassay coefficients of variation were less than 5 and 11%, respectively.