Vanadium in Italian waters: monitoring and speciation of V(IV) and V(V)

In this work, a highly sensitive method was developed to separate vanadium (IV) from vanadium (V), which are both contained in water at trace levels. A suitable strong anionic exchange column (SAX) loaded with disodium ethyle ndiaminetetraacetic acid (Na(2)EDTA) was used to trap both vanadium species dissolved in 10-100 ml of water at pH 3. The vanadyl ion was selectively e luted by means of 15 ml of an aqueous solution containing Na(2)EDTA, tetrab utylammonium hydroxide (TBA(+)OH(-)), and isopropanol (Pr-i-OH) and was sub sequently determined by atomic absorption spectroscopy with electrothermal atomization. The concentration of vanadate ion was calculated by subtractin g the vanadyl concentration from the total concentration of vanadium. The o ptimal conditions for a selective elution were evaluated. The recovery of v anadium (IV) was 95% or better. The proposed method provides a simple proce dure for the speciation of vanadium in aqueous matrices. The collection of the two forms could easily be carried out at the sampling site. Therefore,t he risk of changing the concentration ratio between vanadium species was wi dely reduced. The detection limits were 1 mug/l for both species, when a 10 -ml sample was eluted through the column. The method was applied successful ly to vanadium speciation on different kinds of Italian volcanic water: Mou nt Etna (Sicily), Lake Bracciano and Castelli Romani (Latium). (C) 2000 Els evier Science B.V. All rights reserved.