Spectrophotometric determination of cyanide in aqueous samples after its conversion to thiocyanate and complexation to ferric-thiocyanate

Abstract

A simple spectrophotometric method is developed for the determination of traces of cyanide ion in water samples. Toxic cyanide was reacted with sulfur (S8) dissolved in acetone and converted to non-toxic thiocyanate which is more stable than cyanide also. This product was reacted to Fe (III) to form red ferric-thiocyanate complex. The complex absorption rate in the first two minutes of its formation is related to the cyanide concentration. By measuring the complex absorbance at 465 nm, the cyanide in the range of 2.0-16.0 μg/mL was determined with a detection limit of 1.7 μg/mL. Relative standard deviation (n = 6) for concentrations of 4.0 and 12.0 μg/mL of cyanide was obtained 4.2 % and 1.5 %, respectively. To avoid interferences from other cations and anions, it is possible to isolate cyanide with a system converting CN- to HCN. This method was successfully applied to determine cyanide in various water samples.

Keywords

• spectrophotometry
• cyanide
• thiocyanate
• sulfur
• ferric-thiocyanate