Nonsuppressed Ion Chromatography of Cyanide Ion Using the Reaction with Polysulfide

Abstract

A sensitive method for microdetermination of cyanide ion was developed by nonsuppressed ion chromatography(IC) with UV and conductometric(CD) detection. Cyanide ion- is converted to thiocyanate ion by the reaction with polysulfide ion and the latter is quantitatively determined by nonsuppressed IC using the mixed solution-1.3 mmol⋅dm^-3 in potassium gluconate-5.8 mmol⋅dm^-3 in boric acid-1.3 mmol⋅dm^-3 in sodium tetraborate -12% in acetonitrile 3% in 1-butano1-0.5% in glycerol (pH 8.5)-: as an eluent. Sample solution for ion chromatography was prepared by adding polysulfide four times more than equivalents to cyanide ion, and digesting for 20 min at 90°C in a water bath. The calibration curve for cyanide ion with UV detection (220 rim, 0.04 aufs) was linear in the concentration range of 0.05-2.5 ppm, and also linear with CD detection in the range of 0.25-2.5 ppm. In the case of UVdetection, the relative error of less than 2.2% and relative standard deviation(%) of less than 4.7%were obtained in the concentration range of 0.05-2.5 ppm cyanide. Detection limits of cyanide ion with UV and CD detection were 0.01 ppm and 0.1 ppm, respectively. Five-fold molar excess of common anions such as chloride, bromide, iodide, nitrate, sulfate and thiosulfate, and equimolar amounts of metal cations such as silver, mercury(II), lead(II), zinc, aluminium and iron(III) did not interfere. Presence of iron(II) and copper(II) interfered the determination.