Speciation of vanadium(IV) and (V) in mineral water by anion exchange liquid chromatography-inductively coupled plasma mass spectrometry after EDTA complexation

HPLC with on-line ICP-MS was used for the determination of V(IV) and V(V) in natural mineral water. Cationic and anionic tetravalent and pentavalent vanadium species were converted into V-EDTA complexes, i.e. [VO(EDTA)](2-) and [VO(2)(EDTA)](3-), which could be effectively separated on a short anion exchange column in <6 min. Pre-column EDTA complexation also prevented species interconversion as a result of loss of CO(2) from samples and their exposure to atmospheric oxygen. A low-salt mobile phase (4 mM carbonate buffer and 5 mM EDTA-Na(2)) compatible with ICP-MS detection was used in chromatographic separations. The method was tested on real samples spanning one order of magnitude of V concentrations and encompassing a wide range of potential interfering ions and total dissolved solids, providing accurate and reproducible results. Mass balance budgets gave a mean value of 100% (range 96-107%). Recoveries from spiking experiments were in the range 98-103%. Precision as average intra-day repeatability was 1.2% and 0.9% for V(IV) and V(V), respectively. Average inter-day repeatability was 5.5% and 1.4% for V(IV) and V(V), respectively. Limits of detections were 0.16 mg L(-1) for V(IV) and 0.025 mg L(-1) for V(V). The interference arising by (35)Cl(16)O was resolved chromatographically. V(V) was found to largely predominate in PET-bottled mineral water samples. Species distribution was consistent with theoretical predictions based on thermodynamic equilibria of vanadium in water. Overall, a rapid, sensitive, on-line method is provided which can be readily employed for monitoring purposes.