Liquid–liquid extraction and cloud point extraction for spectrophotometric determination of vanadium using 4-(2-pyridylazo)resorcinol

Abstract

AbstractLiquid-liquid extraction (LLE) and cloud point extraction (CPE) of vanadium(V) ternary complexes with 4-(2-pyridylazo)resorcinol (PAR) and 2,3,5-triphenyl-2H-tetrazolum chloride (TTC) were investigated. The optimal conditions for vanadium extraction and spectrophotometric determination were identified. The composition (V : PAR : TTC) of the extracted species was 1 : 2 : 3 (optimal conditions; LLE), 2 : 2 : 2 (low reagents concentrations; LLE), 1 : 1 : 1 (short heating time; CPE), and 1 : 1 : 1 + 1 : 1 : 0 (optimal extraction conditions; CPE). LLE, performed in the presence of 1,2-diaminocyclohexane-N,N,N’,N’-tetraacetic acid and NH4F as masking agents, afforded the sensitive, selective, precise, and inexpensive spectrophotometric determination of vanadium. The absorption maximum, molar absorptivity, limit of detection, and linear working range were 559 nm, 1.95 × 105 dm3 mol−1 cm−1, 0.7 ng cm−3, and 2.2-510 ng cm−3, respectively. The procedure thus developed was applied to the analysis of drinking waters and steels. The relative standard deviations for V(V) determination were below 9.4 % (4-6 × 10−7 mass %; water samples) and 2.12 % (1-3 mass %; steel samples).