Cloud Point and Solid Phase Extraction of Vanadium in Surface and Bottled Mineral Water Samples Using 8-Hydroxyquinoline as a Complexing Reagent
S. Khan, T.G. Kazi*, J.A. Baig, N.F. Kolachi, H.I. Afridi, S. Kumar, A.Q. Shah and G.A. Kandhro
National Center of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, Pakistan
Cloud point extraction (CPE) and solid phase extraction (SPE) methods were developed for the determination of µg l-1 of vanadium ions in surface, tap and bottled mineral water samples, based on the rapid reaction of vanadium(V) with 8-hydroxyquinoline (8-quinolinol) at pH 3-5. Both the sensitive extraction methods were successfully employed for the preconcentration of V in real samples. For CPE, V complexed with 8-quinolinol and then was entrapped in non-ionic surfactant Triton X-114, while for SPE, V was adsorbed on XAD -2 impregnated with 8-quinolinol. The experimental conditions for SPE (pH, eluent, and contact time between the liquid sample and the resin) and CPE (pH of sample solution, concentration of 8-quinolinol and Triton X-114, equilibration temperature and time period for shaking) were investigated in detail. The validity of SPE/CPE of V was checked by certified reference material of water (SRM-1643e). The extracted surfactant-rich phase (200 µl) was mixed with 200 µl of HNO3 in ethanol and this final volume was injected into electrothermal atomic absorption spectrometry with different modifiers. Under these conditions, the preconcentration of 25 ml sample solution allowed the raising of an enrichment factor of 100 and 10 folds for CPE and SPE, respectively. The concentration of V in surface water (river and lake), tap water and bottled mineral water samples was found to be in the range of 1.30-19.9, 1.05-5.25 and 0.67-1.21 µg l-1, respectively.
Keywords: Vanadium, Surface and bottled mineral water samples, 8-Quinolinol, XAD-2, Triton X-114, Cloud point extraction