RESUMEN
With regard to routine analyses in market control, the authors recommend two methods (according to the expected amounts of active principle) for the determination of thiabendazole residues on citrus fruits and bananas. The ultraviolet spectrophotometric method is preferable in determining thiabendazole contents of more than 1 p.p.m., if the cleaning operations described are respected. For the detection of thiabendazole and for the determination of amounts of less than 1 p.p.m. (the tolerance limit being 0.2 p.p.m. for pomes, berries, stone fruits, kernel fruits and also for potatoes) the thin-layer chromatographic method seems likewise to be suited (also in considering that it is semi-quantitative by nature); especially since the spectrophotometric method yields values by 0.2 p.p.m. too high (due to the measurement of residual absorption of vegetable constituents). The authors are of opinion that such an error must be considered to be too high for contents lower than 1 p.p.m.
