Simplified Colorimetric Determination of Thiocyanate in Biological Fluids, and Its Application to Investigation of the Toxic Amblyopias

Abstract

A colorimetric procedure for determination of small amounts of cyanide and thiocyanate, involving the synthesis of a pyridine dyestuff by the reaction of pyridine and an aromatic amine, has been simplified for the estimation of thiocyanate alone in biological fluids. Replacement of benzidine with p-phenylenediamine in the colorimetric reaction has both improved the precision of the analytical procedure and avoided a carcinogenic hazard. This method has been used to follow the decrease in plasma thiocyanate associated with abstinence from cigarette smoking, and its subsequent increase upon resumption. It has also been used to measure the plasma and urinary thiocyanate concentrations of patients suffering from the particular toxic amblyopias—tobacco amblyopia and Leber’s hereditary optic atrophy— believed to be associated with cyanide toxicity, and to follow the increased thiocyanate concentrations that accompany significant improvements in the patients’ vision brought about by various treatments.