Abstract
A fast and robust sequential injection analysis (SIA) methodology for routine determination of V(V) in environmental polluted waters is presented. The determination was based on the oxidation of dopamine (DP) by V(V) in acidic medium followed by coupling of the formed intermediary with 4-aminoantipyrine (4AAP) to yield a violet product (ë=565 nm). The operation mode of the SIA system allowed the implementation of a stopped flow procedure in which the reaction zone was stopped for 180 s in the reaction coil before reaching the   spectrophotometric detector, with the aim of increasing the sensitivity.Linear calibration plots were obtained for V(V) concentrations between 0.50 and 5.0 mg..-1. The developed methodology exhibits a good precision, with relative standard deviation (rsd) < 2.0% (n=15) and the detection limit was 0.39 mg..-1. The presented SIA methodology was applied to the determination of V(V) in 10 water samples and in a wastewaterreference certified sample. The determination of V(V) by the developed automatic procedure involved the consumption of 1.9 mg of 4AAP and2.9 mg of DP and the production of 2.35 m. of effluent.
Highlights
Vanadium is a metallic element widely distributed in nature that in vestigial amounts is an essential element for cell growth, and is important for the prevention of some heart diseases
All studies related to the optimisation of the physical and chemical parameters involved in the determination of V(V), in the sequential injection analysis (SIA) automatic system, as well as the results from V(V) determination in water and their validation, are described below
The SIA methodology developed for the determination of V(V) in water was based on a reaction presented by Kumar et al (2007) in which the reagent MBTH was changed by 4AAP
Summary
Vanadium is a metallic element widely distributed in nature that in vestigial amounts is an essential element for cell growth, and is important for the prevention of some heart diseases. To overcome some of these drawbacks some flow injection analysis (FIA) methodologies have been proposed for the determination of V(V) in environmental water samples Some of these methodologies involved the speciation (Yamane et al, 1998) and/or pre-concentration (Matsuoka et al, 1995; Yang et al, 1996; Wuilloud et al, 2001; Moyano et al, 2006) of V(V) and V(IV), but most of them are spectrophotometric procedures based on reactions in which V(V) is able to catalyse the oxidation of several compounds (Nakano et al, 1989; Ensafi and Kazemzadeh, 1996; Shiobara et al, 1999; Nakano et al, 2002). To prepare the SIA system for the analytical determinations a small preliminary procedure was performed in order to fill the connecting tubing with carrier solution and the inlets of the selection valve with the respective solutions. After the stop period the reaction zone was sent to the detector (Step 6) and a signal, of absorbance proportional to the concentration of V(V), was registered
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