An improved method for determination of thiocyanate in plasma and urine

An improved spectrophotometric method is described for the determination of thiocyanate in plasma and urine. Thiocyanate is adsorbed on a weak anion-exchange resin with strong affinity for chaotropic ions, and eluted with perchlorate. Thiocyanate is then chlorinated by hypochlorite and quantified according to the König (J Prakt Chem 1904; 69:105-37) reaction by use of isonicotinic acid and 1,3-dimethyl-barbituric acid. The method affords a simple, rapid and sensitive assay for thiocyanate and has a detection limit of 0.93 mumol/l. At thiocyanate concentrations of 107.1 and 167.4 mumol/l in plasma and urine the within-day CVs were 0.69% and 1.1% respectively, and the total imprecision measured for a period of 65 days was 0.98%. Analytical recoveries were quantitative both with urine and plasma samples.