Abstract: A catalytic spectrophotometry for the determination of trace vanadium(V)based on its catalytic effect on discoloring reaction of oxidation of arsenazoⅢ(AsAⅢ)with potassium bichromate in a weak acid medium is described,and the addition of Triton X-100 can further increase the sensitivity of the reaction and its catalytic extent is linear with the content of V(V).The reaction rate is monitored spectrophotometrically by measuring the decrease in absorbance of AsAⅢat 550 nm after a fixed time(8 min).The calibration graph is linear in the range of 0.0～20.0μg/L vanadium(V)and the detection limit of the method is 0.15μg/L.Combined with ion-exchange resin separation.The method has been successfully applied to the determination of V(V) in food samples with the relative standard deviation of 1.18%～4.00% and the recovery of 97.5%～102.5%.The results are in good agreement with those provided by AAS method.The method has also been applied to the determination of V(V)in human hair,plant and tea samples,and the results are in agreement with certified values.

Key words: vanadium(Ⅴ), kinetic spectrophotometry, arsenazo Ⅲ, potassium bichromate