Solid phase extraction and spectrophotometric determination of vanadium

A sensitive, selective and rapid method has been developed for the determination mug/L level of vanadium based on the rapid reaction of V(V) with 2-(2-quinolylazo)-5-dimethylaminophenol (QADMAP) and the solid phase extraction of the colored chelate with C-18 cartridge. QADMAP reacts with V(V) in the presence of citric acid-sodium hydroxide buffer solution (pH=3.5) and cetyl trimethylammonium bromide (CTMAB) medium to form a violet chelate of a molar ratio 1:2 (V:QADMAP). This chelate is enriched by solid phase extraction with C-18 cartridge and the enrichment factor of 50 was obtained by elution of the chelate from the cartridge with ethanol. Molar absorptivity of the chelate has been found to be 1.22 x 10(5) L.mol(-1).cm(-1) at 585 nm. Beer's law is obeyed in the range of 0.01-0.6 mug/mL. The detection limit is 0.04 mug/L in original samples. This method has also been applied to the determination of V(V) in water and biological samples. The relative standard deviations are 1.8-2.5%, and the recoveries are 96-103%.