An inexpensive and fast vanadium [(IV), (V)] speciation method was performed by using optical chemical sensor that incorporates lipophilized calmagite (Cal) with cetyl pyridinium chloride (CPC) as a suitable ligand on triacetylcellulose membrane in aqueous solutions prior to UV-Vis spectrometric determination. Absorbance decrease of the optode in pH 6 at 490 nm depended on the V(V) ion concentration. The V(IV) content was found after oxidation to V(V) at the mentioned conditions. Two aliquots of sample were used for speciative determination of V(V) and V(V) + V(IV) mixture. With the optimized proposed sensor V(V) and V(IV) can be assayed with detection limits of 0.002 and 0.003 nmol L−1, respectively. The optode was tested by analysing several mixtures containing different ratios of V(V) + V(IV) and was found to be highly reproducible. The validity of the method was checked via spiked water samples with total relative standard error less than 4%.
vanadium; speciation; calmagite; ion pair; optode
