Spectrophotometric determination of thiocyanate following complexation with mercury(II) and N-phenylbenzohydroxamic acid
A simple solvent extraction and spectrophotometric method for the determination of trace amounts of thiocyanate is described. Thiocyanate is selectively separated from other ions by reaction with mercury(II). The excess of mercury(II) is determined using N-phenylbenzohydroxamic acid (PBHA) at pH 6.8 and the thiocyanate concentration calculated. Mercury(II) complexes rapidly with PBHA in ethanol and is further extracted into chloroform. Beer's law is obeyed for thiocyanate in the range 0–10 p.p.m. at 550 nm for a fixed amount, 20 p.p.m., of mercury(II). The method has been applied to the determination of thiocyanate in human blood serum, urine and some organoisothiocyanate samples.