Development of a high sensitivity photometric procedure for the determination of vanadium in mineral and fresh waters employing a downsized multicommuted flow analysis approach
This article focuses on the development of an analytical procedure for the photometric determination of vanadium in fresh and mineral waters, implemented employing a downsized multicommuted flow analysis approach. A flow system module using solenoid mini-pumps for fluid propelling and a light emitting diode (LED) based photometer were handled employing a microcontroller (PIC18F). Aiming to improve sensitivity, the flow analysis module and the photometer were designed to allow the coupling of a flow cell with an optical pathlength of 150 mm. The photometric procedure was based on the reaction of V(IV) with eriochrome cyanine R, which formed a compound that presented maximum absorption at 560 nm. Samples of river water and mineral water were processed with the intention to assess the effectiveness of both equipment setup and analytical procedure. The proposed setup presented good overall performance including a linear response (r = 0.997) comprising the concentration range of 0.02 to 1.50 μg mL−1 vanadium; reagent consumption of 11.6 μg eriochrome cyanine R and 8.6 mg ascorbic acid per determination; and a detection limit of 13 μg L−1 vanadium. Other useful features including a relative standard deviation of 0.87% (n = 10), a sampling throughput of 47 determination per hour and a waste generation of 2.4 mL per determination were also achieved.