Abstract: A study of the behavior of fuberidazole (FBZ) (2-(2-furyl)benzimidazole), and thiabendazole (TBZ) (2-(thiazol-4-yl)benzimidazoie) in a sequential injection system with a fluorimetric detector has been performed. Several variables such as pH, composition of buffers, volumes of sample and reagents, addition order, geometry of mixing coil and spectrofluorimetric parameters have been optimized. A pH 2 buffer solution was found to be optimal for both FBZ and TBZ. The calibration graphs are linear between 0.04 and 10 µg L-1 for FBZ and between 0.08 and 20 µg L-1 for TBZ with 3s detection limits of 0.012 and 0.02 µg L-1, respectively. The relative standard deviation (n = 10) was 0.3% for 1 µg L-1 of FBZ and 0.5% for 2 µg L-1 of TBZ. Resolution of the system was carried out by applying a multiple linear regression (MLR) calibration model. The method was applied to the determination of both fungicides added to natural waters. Recoveries between 96 and 106% were achieved.

Abstract: An automated and versatile sequential injection spectrofluorimetric procedure for the simultaneous determination of multicomponent mixtures in micellar medium without prior separation processes is reported. The methodology is based upon the segmentation of a sample slug between two different buffer zones in order to attain both an improvement of sensitivity and residual minimization for the whole species. Resolution of overlapping fluorescence profiles is achieved using a variable angle scanning technique coupled to multivariate least-squares regression (MLR) algorithms at both sample edges. The potentialities of the described methodology are illustrated with the spectrofluorimetric determination of four widespread pesticides with different acid-base properties; viz. carbaryl (CBL) (1-naphthyl-N-methylcarbamate), fuberidazole (FBZ) (2-(2-furyl)benzimidazole), thiabendazole (TBZ) (2-(4-thiazolyl)benzimidazole) and warfarin (W) (3-α-acetonylbenzyl)-4-hydroxycoumarin. Detection limits at the 3s level were 3.9, 0.02, 0.03 and 10 µg L-1 for CBL, FBZ, TBZ and W, respectively at the maximum sensitivity pH. Dynamic ranges of 13-720 µg L-1 CBL, 0.10-14 µg L-1 FBZ, 0.19-60 µg L-1 TBZ and 0.05-5 mg L-1 W were achieved. Relative standard deviations (n = 10) were 0.2% for 100 µg L-1 CBL and 2.4 µg L-1 FBZ, 0.7% for 8 µg L-1 TBZ and 1.0% for 1 mg L-1 W. The proposed automated methodology, which handles 17 samples/h, was validated and applied to spiked real water samples with very satisfactory results. (C) 2002 Elsevier Science B.V. All rights reserved.

Abstract: A stopped-flow sequential injection (SI) spectrofluorimetric procedure is presented for the simultaneous on-line determination of Carbaryl (CBL) (1-naphthyl-N-methylcarbamate), Fuberidazole (FBZ) (2-(2 -furyl)-benzimidazole), Thiabendazole (TBZ) (2-(4 -thiazolyl)-benzimidazole) and Warfarin (W) (3-α-acetonylbenzyl)-4-hydroxycoumarin) (Fig. 1) in micellar medium through the chemometric resolution of the recorded variable angle scanning (VAS) spectra.