Spectrophotometric Determination of Cyanide Based on Berthelot Reaction

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Abstract
The proposed spectrophotometric method for the determination of cyanide involves conversion of cyanide to cyanate using sodium hypochlorite followed by acid hydrolysis to form ammonium sulphate. The formed ammonium sulphate is determined based on Berthelot reaction using salicylic acid, sodium hypochlorite, and sodium nitroprusside. The λmax for the formed dye is at 648 nm and the calculated molar absorptivity is 1.8 × 104 L mol−1 cm−1. Beer's law is obeyed in the concentration range 0–5 µg and the relative standard deviation is 2.2% for n = 10 at 0.3 ppm of CN−. The developed method was applied for the determination of cyanide in the hypochlorite/H2O2 treated electroplating effluents and sludges. The results obtained in the developed method compares well with the pyridine–barbituric acid method and by recovery studies of added cyanide.