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Immunoassay for carbamothioate detection and application to enhanced pesticide degradation
Abstract
Simple, inexpensive immunoassays have been developed for rapid detection of pesticide residues in soil and water. An indirect enzyme-linked immunosorbent assay (ELISA) for EPTC was developed that may be useful for predicting enhanced carbamothioate herbicide degradation in adapted soils. A modified radioimmunoassay (RIA) procedure was developed to detect antibodies specific for EPTC and establish appropriate antibody dilutions for optimum ELISA sensitivity. Antibodies from a rabbit injected with a butylate-analog protein conjugate were used in the RIA. The RIA detection range was 100 to 1000 ng mL$\sp{-1}$ and EPTC recovery from fortified soil samples was $>$96% when EPTC was extracted with 90:10 (v/v) of acetonitrile:water. An indirect ELISA subsequently was developed with an EPTC detection range of 10-1280 ng mL$\sp{-1}$ in a 1:3 aqueous dilution of the 90:10 soil extract. Although ELISA detection of residual EPTC was less quantitative and more variable than conventional gas chromatography, the assay could provide a rapid, cost-effective method for screening soils to determine enhanced carbamothioate degradation. The ELISA was superior to phosphodiesterase, rhodanese and urease soil enzyme assays and a fluorescein diacetate assay in detection of enhanced carbamothioate degradation. Inhibition of phosphodiesterase did not prevent rapid EPTC degradation in adapted soils but EPTC degradation was slowed in adapted soils containing rhodanese and urease inhibitors. Rhodanese and urease may be involved in enhanced carbamothioate degradation or inhibitors of the enzymes may be affecting other processes critical to enhanced carbamothioate degradation. Differences in soil enzyme activity may be transient and measurable only for a short time after herbicide application. Alternatively, structurally altered enzymes, not discernible by standard soil enzyme assays, may be involved in enhanced carbamothioate degradation. In a separate study, a commercial cholinesterase-inhibitor detection kit was accurate for the residues of the insecticide carbofuran in water samples as confirmed by gas chromatography.
Subject Area
Agronomy
Recommended Citation
Hutchinson, Pamela J, "Immunoassay for carbamothioate detection and application to enhanced pesticide degradation" (1991). ETD collection for University of Nebraska-Lincoln. AAI9211471.
https://digitalcommons.unl.edu/dissertations/AAI9211471