A sensitive, selective and rapid method has been developed for the determination micrograms per liter level of vanadium ion based on the rapid reaction of vanadium(V) with 2,3-dichloro-6-(2,7-dihydroxy-1-naphthylazo)quinoxaline (DCDHNAQ) and the solid phase extraction of the colored complex with C18 cartridge. The DCDHNAQ reacts with V(V) in the presence of citric acid-sodium hydroxide buffer solution (pH 3.3) and benzyldimethyl tetradecylammonium chloride (zephiramine) medium to form a violet complex of a molar ratio 1:2 [V(V) to DCDHNAQ]. This complex was enriched by solid phase extraction with C18 cartridge and the enrichment factor of 100 was obtained by elution of the complex from the cartridge with acetonitrile. The molar absorptivity and Sandell sensitivity of the complex are 2.45x10(5) L mol(-1) cm(-1) and 0.0208 ng cm(-2) at 573 nm in the measured solution. Beer's law is obeyed in the range of 0.01-0.45 microg mL(-1), whereas Ringbom optimum concentration ranges found to be 0.025-0.425 microg mL(-1). The detection and quantification limits are 3.2 and 9.9 microg L(-1), respectively in the original samples. This method was applied to the determination of vanadium(V) in steel, soil, water and biological samples with good results.
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