Complementation of direct-injection high-performance liquid chromatography and enzyme-linked immunosorbent assay for the analysis of thiabendazole in fruit juices and concentrates.

The fungicide thiabendazole was quantified in fruit juices and their concentrates (bulk and store bought) without clean-up by simply injecting 50 microliters of dissolved sample into an HPLC. This novel method used a mobile phase consisting of acetonitrile-methanol-water-ethanolamine (37:11:52:0.02) and was passed through a C18 column at 1 ml/min. Detection was accomplished by fluorescence at 305 nm excitation and 345 nm emission. Using peak height thiabendazole was linear from 0.032 to 2.05 ng injected. The limit of quantitation was 5 ppb for juices and store concentrates (2.0 ppb for the limit of detection), 10 ppb for bulk apple concentrates and 25 ppb for other bulk concentrates (5 and 10 ppb, respectively for the limit of detection). Intra- and interassay percent relative standard deviations for standards and samples were mostly below 7% with none above 9%. Eighty-four juices and concentrates out of 200 analyzed were found to contain thiabendazole (2-2560 ppb) by HPLC and all were shown to be thiabendazole positive by enzyme-linked immunosorbent assay (ELISA). The HPLC vs. ELISA correlation coefficient was 0.984.