Electrothermal atomic absorption spectrometric determination of vanadium(V) in soil after leaching with Na2CO3

Vanadium(V) is a potentially dangerous chemical pollutant, which coexists in the natural environment with V(IV) species. A method of selectively leaching V(V) species from soil is presented in this work, wherein samples are treated with 0.1 M Na2CO3. The amount of V(V) species "liberated" is proportional to the concentration of CO32- ions; 0.1 M Na2CO3 was found to be optimum. It was also shown that V(V) compounds are leached from soil in the presence of CO2. The sum of V(V) and V(IV) in all soil samples was found to be in good agreement with the total content of vanadium in all soil samples after HF–H2SO4–HClO4 digestion. The limit of detection for determination of vanadium is soil by electrothemal atomic absorption spectrometry was found to be 0.5 (mu)g g-1. The method was applied to the determination of V(V) in Certified Reference Material Marine Sediments MESS-3 and PACS-2 (National Research Council of Canada). Of a total vanadium content of 243 and 133 (mu)g g^-1, 15 and 8 (mu)g g^-1 is present as V(V) species in CRM MESS-3 and PACS-2, respectively. Results of V(IV) and V(V) determination in soils, taken near a vanadium mine in the North West Province of South Africa show that the concentration of V(V) species in some samples is relatively high, up to 2700 (mu)g g^-1, and varies from 0.6 to 50.8% of the total amount of vanadium.