Determination of cyanide by an indirect spectrophotometric method using formaldehyde and 3-methyl-2-benzothiazolinone hydrazone

A simple spectrophotometric method to determine cyanide based on the reaction between cyanide - formaldehyde-3-methyl-2-benzothiazolinone hydrazone is proposed. The method is useful for determining cyanide in the concentration range 0-0.2 ppm with a standard deviation of 3.5% for n = 10 at 0.06 ppm of CN- and the calculated molar absorptivity is 4.3 x 10(4) L mol(-1) cm(-1). Response of the proposed method for cyanide determination in the presence of potential interferents is evaluated. The method is practically free from the interference of thiocyanate in the presence of high concentration of nitrite and nitrate. The proposed method has been successfully applied to determine free and total cyanide in effluent samples and in soil sample taken from treated cyanide dump. The results are validated with the barbituric acid method and by standard addition.