A novel indicator reaction for the catalytic determination of V(V) at ppb levels by the kinetic spectrophotometric method

Abstract

Abstract:A novel sensitive and relatively selective kinetic method is presented for the determination of V(V), based on its catalytic effect on the oxidation reaction of Ponceau Xylydine by potassium bromate in presence of 5-sulfosalicylic acid (SSA) as activator. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of Ponceau Xylydine at 640 nm between 0.5 to 7 min (the fixed time method) in H 3 PO 4 medium at 25 o C. The effect of various parameters such as concentrations of H 3 PO 4 , SSA, bromate and Ponceau Xylydine, temperature and ionic strength on the rate of net reaction were studied. The method is free from most interferences, especially from large amounts of V(IV). The decrease in absorbance is proportional to the concentration of V(V) over the entire concentration range tested (1-15 ng mL −1 ) with a detection limit of 0.46 ng mL -1 (according to statistical 3S blank /k criterion) and a coefficient of variation (CV) of 1.8% (for ten replicate measurement at 95% confidence level). The proposed method suffers few interferences such as Cr(VI) and Hg(II) ions. The method was successfully applied to the determination of V(V) in tap water, drinking water, bottled mineral water samples and a certified standard reference material such as SRM-1640 with satisfactory results. The vanadium contents of water samples were also determined by FAAS for a comparison. The recovery of spiked vanadium(V) was found to be quantitative and the reproducibility was satisfactory. It was observed that the results of the SRM 1640 were in good agreement with the certified value.

A kinetic spectrophotometric method for vanadium(v) determination in food samples using a Janus Green-bromate system

“…24,25 The published catalytic-spectrophotometric methods for the determination of vanadium(V) were reviewed and summarized in Table 1. 23, As given in Table 1, the developed method surpasses kinetic methods in the linear dynamic range 31,37,39,48 for vanadate determination.…”