Detection of chemical residues in tangerine juices by a duplex immunoassay.

A rapid duplex ELISA for the simultaneous determination of two of the most widely used organophosphorous insecticides in tangerine juices is described. To accomplish this aim, two individual enzyme-linked immunosorbent assays for chlorpyrifos and fenthion pesticides were integrated into one ELISA test. The strategy uses 96-well plates with specific wells coated with the corresponding haptenized conjugate. The optimized duplex ELISA was accomplished within 40 min achieving a detection limit of 0.20±0.04 µg/L and 0.50±0.06 µg/L, for chlorpyrifos and fenthion, respectively in tangerine juice samples. The determination of residues of both pesticides was carried out by simple sample dilution, without any extra sample clean-up procedure. Results of testing precision, stability, and selectivity demonstrated that the assay provided reliable analytical performances for the simultaneous determination of residues of chlorpyrifos and fenthion in fruit juice samples below the established European maximum residue limits (MRL). In addition, the accuracy and reliability of this duplex bioanalytical method is demonstrated by analyzing blind spiked juice samples and the results, correlated well with those achieved using a well-established GC/MS method (recoveries between 95% and 106%).