Catalytic fading spectrophotometry for the determination of trace molybdenum(VI) in fly ash

A new catalytic spectrophotometric method was established for the determination of trace molybdenum(Ⅵ),based on the catalytic effect of trace molybdenum(Ⅵ) on the oxidative discolouration of ethyl violet(EV) by hydrogen peroxide in the medium of 0.01 mol/L sulfuric acid.The effects of reaction medium,reagent dosage,reaction temperature,reaction time and interference ions on the determination had been discussed,and the optimal reaction conditions had been estabilished.The results showed that the maximum absorption wavelength of the system was 590 nm and the detection limit was 0.11 μg/L.Beer's law was obeyed in the range of 0-500 μg/L for molybdenum(Ⅵ).The proposed method has been applied to the determination of trace molybdenum(Ⅵ) in fly ash,and the results were in good agreement with those obtained by spectrophotometric method with the relative standard deviation of smaller than 3 %(n=6).