Use of a solid sensing zone implemented with unsegmented flow analysis for simultaneous determination of thiabendazole and warfarin

For the first time, a solid sensing zone implemented with unsegmented flow analysis is described for the simultaneous determination of two pesticides, thiabendazole and warfarin. The system works as a simple and rapid spectrofluorimetric biparameter sensor. The sensor is based on the retention of the analytes on the sensing solid zone (octadecyl silane C₁₈ gel) placed in the detection zone itself into a quartz flow-cell. A temporary sequentiation in the arrival of the analytes to the sensing zone is achieved by on line separation using a pre-column of the same gel placed just before the flow cell. Thiabendazole is determined the first (using methanol 30% (v/v) as carrier/elution solution) because it passes through the pre-column while warfarin is strongly retained in it. Then, warfarin is conveniently eluted from the pre-column (using methanol 50% (v/v) as carrier/elution solution) the intrinsic fluorescence peak height measured at an excitation wavelength of 309 nm and an emission wavelength of 368 nm is used as analytical signal. Using a low sample volume (40 μl), the analytical signal showed a very good linearity in the range 10-800 ng ml⁻¹ and 2-40 μg ml⁻¹ with detection limits of 2.35 ng ml⁻¹ and 0.54 μg ml⁻¹ for thiabendazole and warfarin, respectively. The sensor was satisfactorily applied to the determination of these two analytes in pesticides and pharmaceutical preparations.