Determination of Procymidone in vegetables by a commercial competitive inhibition enzyme immunoassay

Abstract

An ELISA commercial kit was used to quantitate residues of Procymidone at very low levels (< 20 μg/kg) in pepper samples. Samples were extracted with ethyl acetate-sodium sulphate and an aliquot is evaporated to dryness and reconstituted in 10 ml of light petroleum. Sample clean up is accomplished by aspirating 2 ml of the light petroleum extract through a silica gel solid phase disposable cartridge. Following aspiration, the sample was eluted with 2 ml of ethyl ether-petroleum ether (1:1). The eluted fraction was evaporated and dissolved with sonication in 2 ml of water before immunoassay analysis. The limit of Procymidone detection was 0.6 μg/kg. The assay logarithmic response was linear from 5 to 80 μg/kg of Procymidone residue. Intra-assay percentage coefficients of variation (%C.V.) ranged from 3.5 to 18.0 and inter-assays %C.V.s varied from 8.0 to 16.0. Comparison studies between gas chromatography with electron capture detection and ELISA analyses showed an acceptable coincidence at levels of 8 μg/kg. However, lower levels of ca. 2 μg/kg were detectable by ELISA only. No cross-reactivity problems were found in the ELISA test associated with the presence of other dichloroaniline derivatives and other pesticides studied.