Simultaneous determination of fluorophores with overlapped spectra by sequential injection analysis coupled to variable angle scanning fluorescence spectrometry and multivariate linear regression algorithms

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 3 σ 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.