棓花青褪色光度法测定电镀废水中的铬(Ⅵ)

在硫磷混酸介质 ,10 0℃恒温水浴中 ,铬 (Ⅵ )能氧化花青显著褪色 ,据此建立了测定铬 (Ⅵ )的新方法。铬(Ⅵ )的浓度在 0～ 1 0 4μg mL范围内符合比耳定律 ,表观摩尔吸光系数为 1 90× 10 4L mol·cm。此法用于测定电镀废水中铬 (Ⅵ )的含量 ,结果令人满意     

Catalytic determination of ultratrace chromium based on gallocyanine‐hydrogen peroxide indicator reaction

A highly sensitive catalytic procedure for the determination of ultratrace chromium(VI) was developed based on its catalytic effect on the oxidation of gallocyanine by hydrogen peroxide in hexamine‐hydrochloric acid buffer solution. The reaction was followed spectrophotometrically by measuring the rate of change in the absorbance at 620 nm. The apparent active energy of the catalytic reaction is 6.84 kJ . mol^‐1. The calibration graph is linear for 0–150 ng.ml^‐1, and the detection limit is 0.8 ng.ml^‐1. Most foreign ions have no interfering effect on the determination of chromium(VI) except for Al³⁺, Cu²⁺, Fe³⁺and Fe²⁺. The interference of Al³⁺ is eliminated by masking with F^‐, and those of Cu²⁺, Fe³⁺ and Fe²⁺ are eliminated by adding appropriate amount of EDTA. The present procedure had been used for the determination of trace chromium(VI) in lake water, mine water and electroplating wastewater, and the results were satisfactory.