Comparison of Enzyme-Linked Immunoassay with Gas Chromatography/Mass Spectrometry for Analysis of the Cotton Herbicide Fluometuron

Abstract

The cotton herbicide fluometuron was assayed using an enzyme-linked immunosorbent assay (ELISA) of edge-of-field runoff samples collected during 1997. Results were compared with concentrations of fluometuron and a primary fluometuron metabolite, demethylfluometuron, measured by gas chromatography/mass spectrometry (GC/MS). ELISA data were obtained for almost 200 samples; GC/MS analyses were made on approximately 20% of these. Fluometuron concentrations, as determined by ELISA, ranged from undetected to 193 Îg/L (micrograms per liter). Fluometuron concentrations by GC/MS ranged from undetected to 127 Îg/L. In all cases in which fluometuron was detected by GC/MS, it was also detected by ELISA, and all fluometuron detections by ELISA were confirmed by GC/MS. Overall correlation of ELISA concentrations with GC/MS gave an Rî (R squared) value of approximately 0.79; a linear regression resulted in a slope greater than 1.0, indicating that fluometuron concentrations measured by ELISA were higher than those measured by GC/MS. This was likely caused by the presence of compounds that cross reacted with the ELISA antibodies. Products of fluometuron degradation and phenylurea herbicides, which were chemically similary to fluometuron, were investigated for contribution to concentrations measured by ELISA, but significant cross reactivity by these compounds was not indicated.

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Bastian, K.C., Thurman, E.M., and Rebich, R.A., 1998, Comparison of enzyme-linked immunoassay with gas chromotography/mass spectrometry for analysis of the cotton herbicide fluometuron, in Daniel, B.J., ed., Proceedings of the Twenty-Eighth Mississippi Water Resources Conference, April 7-8, 1998, Raymond, Mississippi: Mississippi State, Water Resources Research Institute, p. 45-55.

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