Determination of cyanide, thiocyanate, cyanate, hexavalent chromium, and metal cyanide complexes in various mixtures by ion chromatography with conductivity detection

ABSTRACT

The first aim of this study was to develop a selective, sensitive, and reliable method for direct simultaneous determination of cyanate, thiocyanate, and hexavalent chromium by ion chromatography (IC) with conductivity detection. The other target was to successfully determine cyanides by utilizing same chromatographic system. Yet, since cyanides can not be detected by the direct method, free cyanide ions were converted into cyanate with chloramine-T at alkaline pH. In addition, strongly complexed metal cyanides were converted into cyanate by using photo-oxidation following chloramine-T. Total cyanate ion obtained from developed methods were analyzed with IC. The chromatographic separations on anion exchange column were accomplished by optimized multistep gradient eluent program using NaOH as the eluent. Proposed method was applied for the simultaneous determination of cyanide and hexavalent chromium in electroplating bath solutions and in industrial wastewater. Cyanide and hexavalent chromium could be measured in the linear dynamic ranges of 0.6–961.5 and 0.9–118.5 µmol L⁻¹, respectively. The limit of detection and limit of quantification of cyanide were 0.18 and 0.61 µmol L⁻¹, and these values for chromium(VI) were 0.26 and 0.86 µmol L⁻¹, respectively.

GRAPHICAL ABSTRACT

KEYWORDS:

• Chromate
• cyanate
• cyanide
• ion chromatography
• metal cyanide complexes
• thiocyanate