Gas chromatography-mass spectrometric identification of cyanide using a nucleophilic substitution based derivatization with S-phenyl benzenethiosulfonate.

A novel, simple and efficient analytical method for GC-MS based identification of cyanide has been developed using a single step nucleophilic substitution based derivatization of cyanide in aqueous medium. The nucleophilic substitution reaction of cyanide with S-phenyl benzenethiosulfonate results in the formation of phenyl thiocyanate as a cyanide derivative and it was found that the relative response of the resultant cyanide derivative was much higher than that of the cyanide derivatives resulting from disulfide based derivatizing agents. The sample preparation protocol for the identification of cyanide in aqueous samples was also optimized with the new derivatizing agent. Derivatization followed by liquid-liquid extraction was employed for the preparation of aqueous samples containing cyanide salts. The resultant samples were subjected to GC-MS analysis for the identification of the cyanide derivative. Under optimized conditions, the detection and quantification limits for cyanide aqueous samples were found to be 0.075 μg mL-1 and 0.25 μg mL-1 respectively. The calibration curve had a linear relationship with y = 0.086x - 0.076 and r2 = 0.997 for the working range of 0.25 μg mL-1 to 50 μg mL-1. The intraday RSDs were between 2.24 and 8.17%, and the interday RSDs were between 2.22 and 12.85%. The method can also be successfully employed for the identification of hydrogen cyanide in aqueous medium. The applicability of the present method was demonstrated by analysing a real sample from apple seed extraction.