Kinetic spectrophotometric determination of vanadium in steels based on the catalytic oxidation of thionine by potassium bromate

A sensitive and selective kinetic spectrophotometric method for the determination of V(V) was developed based on the catalytic oxidation of thionine by KBrO3 in 0.6 mol·L−1 H3PO4 medium. The linear calibration range and detection limit at 25°C were 0-0.5 μg·mL−1 and 0.01 μg·mL−1, respectively. In the presence of NaF and urea, most of the common ions did not interfere with the determination of V(V). The proposed method was applied for the determination of vanadium in steels and satisfactory results were obtained.