Automatic integrated system for catalytic spectrophotometric determination of vanadium in water samples

Abstract

An automatic integrated system implementing a catalytic spectrophotometric method for vanadium determination is presented. Thus, a multisyringe flow injection system (MSFIA) was coupled to a monolithic flow microconduit, called chip (CHIP-MSFIA). All reagents and samples were simultaneously propelled into the chip to achieve complete mixing, heating, and measurement inside it. This catalytic spectrophotometric method is based on the oxidation of gallic acid with bromate catalyzed by V(V). The reaction was followed by measuring the absorbance change at 384 nm. The incorporation of the detection cell inside the thermostatic zone of the chip allows two kinetic–catalytic determination methods: initial rate and fixed time methods. A critical comparison between these two methods at a controlled temperature is presented. Under optimized conditions, the determination of V(V) was performed in the range 0.24–75 μg L⁻¹ achieving limits of detection of 0.33 and 0.24 μg L⁻¹ for fixed-time and initial rate methods, respectively. Relative standard deviations were between 1% and 4%. Finally, the initial rate method was successfully applied to determine the V(V) concentration in natural and waste water samples. Good recoveries were obtained varying from 94% to 102%. Results were compared with those obtained by the reference method (ICP-AES), in order to confirm the accuracy of the CHIP-MSFIA method. Additionally, a certified reference material was satisfactorily analyzed.