DETERMINATION OF CYANIDE BY ION CHROMATOGRAPHY WITH CONDUCTIVITY MEASUREMENT

A highly sensitive analytical method for cyanide was developed by using a conductivity detector in ion chromatography with an alkaline eluent. Dimethylethanolamine (DMEA) as the alkali and formic acid (FA) as the counter ion were good choices in terms of low background conductivity. To shorten the retention time of multi-valence anions such as sulfate and phosphate ion, triethylenetetramine-N,N,N',N'',N''',N'''-hexaacetic acid hexasodium salt (TTHA) was also contained in the eluent. The eluent finally chosen was 20 mM DMEA-1.43 mM FA-20 nM TTHA-0.03 mM borax (pH 10.5). Under these conditions, chloride, cyanide, nitrate, carbonate, phosphate and sulfate were well-separated within 20 min. The detection limit for cyanide was 50 ng/ml. Applications to an environmental sample (river water) and a natural food (apricot) are demonstrated.