Photokinetic voltammetric method for the determination of thiocyanate

Thiocyanate traces have a strong inhibitory effect on the oxidation of Neut ral Red by potassium bromate under UV irradiation in diluted phosphoric aci d. Neutral Red exhibits a sensitive second derivative oscillopolarographic wave at -0.6 V(vs. SCE) in diluted phosphoric acid and sodium acetate solut ion. The oscillopolarographic behavior of Neutral Red was selected as indic ator component for its photo-activated oxidation. The photochemical reactio n rate equation was determined. A detection limit of 0.3 ng mL(-1) (3 sigma /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 ur ine, saliva and serum with satisfactory results.