A simple and rapid method for the determination of thiocyanate in serum

Studies were performed to evaluate ultrafiltration as a means for isolating thiocyanate from serum prior to its colorimetric determination as a ferric chloride complex. Recovery of thiocyanate from serum was enhanced by addition of alkali prior to preparation of the ultrafiltrate, and averaged 96.8%. The reproducibility (CV) of test was 2.3%, within-day; and 3.3%, between-day. The colorimetric reaction was linear to 100 micrograms/mL. The method was tested by determining thiocyanate concentrations in samples collected from smoking and nonsmoking individuals. Thiocyanate concentrations in patient samples, collected after IV-infusion of nitroprusside, were scattered around those of the general population, and ranged from 0.3 to 20 micrograms/mL.