Catalytic discoloration spectrophotometry for determination of trace chromium(VI) in waste water

A new catalytic discoloration spectrophotometry for determination of trace chromium(Ⅵ) was established,which was based on the catalytic effect of trace chromium(Ⅵ) on the oxidative discoloration of ethyl violet (EV) by hydrogen peroxide in a sulfuric acid medium with a pH3.The results showed that the maximum absorption wavelength of the system was 590 nm and the detection limit was 1.01×10-4 mg/L.The Beer′s law was obeyed in a concentration range of 0.05～0.60 mg/L for chromium(Ⅵ).In the presence of sodium fluoride and thiourea,most of common ions do not interfere with the determination of chromium(Ⅵ).This proposed method has been applied to the determination of trace chromium(Ⅵ) in waste water,and the test results are in good agreement with those provided by the titration method with a precision of 4.5% RSD(n=12).