A simple cloud point extraction-spectrophotometric method for total vanadium determination using 4-(2-thiazolylazo)resorcinol and H2O2

A cloud point extraction-chromogenic system for vanadium determination containing 4-(2-thiazolylazo)resorcinol (TAR), H 2 O 2 , H 2 SO 4 , and Triton X-100 was investigated. Optimal conditions for the formation and extraction of a 1:2:1 (V V :O 2 2− :TAR) ternary complex with an absorption maximum at 569 nm were found: concentration of TAR (4 × 10 −5 mol dm −3 ), concentration of H 2 O 2 (1.2 × 10 −4 mol dm −3 ), pH (ca 2), mass fraction of the surfactant (3.6%), and incubation time (40 min). The molar absorptivity ( ε 569 ), Sandell’s sensitivity (SS), limit of detection (LOD) and linear working range (LWR) were 7.4 × 10 4 dm 3 mol −1 cm −1 , 0.69 ng cm −2 , 1.7 ng cm −3 and 6–510 ng cm −3 , respectively. The effect of foreign ions was studied. The developed procedure was applied for the spectrophotometric determination of the total vanadium content in spent silica-supported catalysts and a vanadium-containing dietary supplement. Graphic abstract