RESUMEN
In the present paper, oxalic acid was used to reduce V(V) ion to V(IV) ion, then its complex with V(IV) was formed. By this method, four valence states of vanadium ions had different characteristic absorption peaks in the UV-Visible range. Based on these characteristic absorption peaks, qualitative and quantitative spectrophotometric analysis methods for different valence states of vanadium in vanadium battery electrolyte were established. The results showed that the related coefficients of four standard curves of different valence states were greater than 0.999 0, linearity ranges were 0.326-2.445, 0.326 -2.445, 0.720-5.403, and 1.784-13.437 g x L(-1), respectively. The measurement of samples suggested that the spectrophotometric analysis method was suitable for analyzing the concentration of valence states of vanadium with the RSDs (n = 6) in the range of 0.594%-3.535%.