Kinetic spectrophotometric determination of vanadium (V) based on its inhibitory effect on the thionine ascorbic acid reaction

A simple and sensitive kinetic method for the determination of vanadium(V) based on its inhibitory effect on the reduction of thionine by ascorbic aci d at pH=5 is described. The reaction rate is monitored spectrophotometrical ly by measuring the decrease in absorbance of thionine at 598 nm after a fi xed time (10 min). The calibration graph is linear in the range of 10 - 120 ng ml(-1) of vanadium(V) and the detection limit is 6 ng ml(-1). The relat ive standard deviation (RSD) for 80 ng ml(-1) of V(V) was 0.96 % (n=10). Th e method was successfully applied to the determination of vanadium in a cer tified reference sample.