Abstract
High levels of vanadium have been reported in groundwater (< 0.05 – 5300 g L-1 V) from different parts of Argentina, yet no detailed study of vanadium speciation has been performed. A highly selective strong anion exchange – solid phase extraction (SAX-SPE) method was used (in-situ) for vanadium speciation analysis of groundwater samples from La Pampa - LP (General San Martin and Eduardo Castex) and Buenos Aires - BA (San German) provinces in Argentina. In this method both vanadyl (VIV) and vanadate (VV) were trapped by the complexation with disodium ethylenediaminetetraacetic acid on a pre-conditioned SAX cartridge. In the laboratory, vanadium species were separated at different eluent pH levels. VIV was eluted at pH 4 using methanol and tetrabutylammonium hydroxide. VV was eluted at pH 8 using dihydrogen ammonium phosphate. The eluted species were analysed by inductively coupled plasma mass spectrometry (ICP-MS). This method was validated using an inter-analytical method comparison with HPLC-ICP-MS. A Paired t-test revealed that there was no significant difference (probability, P < 0.05) between the two methods. VV was found to be predominate species in both sample collection areas (LP: 69 – 100%, BA: 33 – 89 % of species) over the range of 158.0 – 4748.0 g L-1 in LP and 88.5 – 504.0 g L-1 in BA. VIV was found at higher levels (29.0 - 301.0 g L-1) in Buenos Aires compared to General San Martin groundwater (4.4 – 161.0 g L-1). The results enhance the potential knowledge of the speciation of vanadium in terms of water quality and human health.