Abstract
Improved analytical methods are described for the determination of total cyanide after separation from thiocyanate (SCN–) and free cyanide [CN–+ HCN (aq)] after separation from hexacyanoferrate [Fe(CN)64– and Fe(CN)63–] and thiocyanate in water by means of a standard continuous-flow system. Separation of total cyanide from thiocyanate is achieved by illumination of samples with visible light, preventing transition of SCN– to CN–, prior to distillation. Separation of free cyanide from hexacyanoferrate and thiocyanate is performed by distillation of samples at pH 4 in a citrate buffer solution in the presence of Cu2+. Distillation under these conditions prevents decomposition of hexacyanoferrate and evaporation of thiocyanate as HSCN. Both methods combine the advantages of samples distillation with a high specificity for total and free cyanide, respectively.
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