Micellar sensitized catalytic kinetic spectrophotometry for highly accurate and reproducible determination of V(IV) and V(V).

A highly accurate and reproducible micellar sensitized kinetic method was proposed for determination of V(VI). The method is based on its catalytic effect on the oxidation of Coomassie brilliant blue R 250 (CBB) by bromate at pH 2.0. The reaction was monitored spectrophotometrically by measuring absorbance change with a fixed-time method of 5 min at 594 and 552 nm with and without surfactant. The variables influencing the calibration sensitivity were extensively investigated, and the optimal conditions were established. The linear calibration range was 10-1,600 μg·L with a relative SD ranging from 0.35 % to 3.35 % (for five replicate measurements of 75, 500, 1,000, and 1,500 μg·L) and a detection limit of 3.8 μg·L. The selectivity was also investigated, and greatly enhanced by suitable masking agents. The method was successfully applied to the analysis of V(IV) in presence of excess V(V) up to 25 fold in environmental waters with the recoveries of 100.0 %-102.8 % for V(IV) and 95.7 %-99.7 % for total V. Its accuracy was validated by analysis of certified reference material via the present kinetic method and standard flame atomic absorption spectrometric method after extractive preconcentration with good agreement between certified and found values. [ABSTRACT FROM AUTHOR]