Photokinetic voltammetric method for the determination of thiocyanate

Thiocyanate traces have a strong inhibitory effect on the oxidation of Neutral Red by potassium bromate under UV irradiation in diluted phosphoric acid. Neutral Red exhibits a sensitive second derivative oscillopolarographic wave at -0.6 V(vs. SCE) in diluted phosphoric acid and sodium acetate solution. The oscillopolarographic behavior of Neutral Red was selected as indicator component for its photo-activated oxidation. The photochemical reaction rate equation was determined. A detection limit of 0.3 ng mL(-1) (3sigma/k) and a linear calibration curve from 2.0-48.0 ng mL(-1) thiocyanate were obtained. The method was applied to the determination of thiocyanate in urine, saliva and serum with satisfactory results.