Application of an enzyme immunoassay for the detection of mecoprop in a groundwater screening procedure

A competitive solid-phase enzyme immunoassay based on rabbit polyclonal antibodies was tested for its reliability. This assay, used for the detection of the phenoxycarboxylic acid mecoprop [2-(4-chloro-2-methylphenoxy-)propionic acid], has already been characterized in terms of middle of the test (0.36 mug/L at 50% B/B-0) and detection limit (0.06 mug/L at 80% B/B-0) by Weber (Acta hydrochim. hydrobiol. 22, 53-59 (1994)). For the reliability test, a small number from a batch of one hundred groundwater samples were spiked. The analyst was neither aware of which nor of how many samples were spiked. The spiked samples were all detected as positive. There were no false negative results. From these findings, values of I were obtained for the diagnostic sensitivity and for the diagnostic specificity. Based on these results, the mecoprop contents of 228 groundwater samples from various waterlevel gauges of a test field were determined. The test site had previously been treated repeatedly with this herbicide. Confirmation of the enzyme immunoassay results was carried out by GUMS. This showed that the enzyme immunoassay gave one false positive result only. All other results from immunoassay and GC/MS showed good correlation.