Flow-injection spectrophotometry of manganese by catalysis of the periodate oxidation of 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)

A sensitive flow-injection spectrophotometric procedure is proposed for the determination of manganese(II), based on its catalytic effect on the oxidation of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) with periodate. By monitoring the change in absorbance of the oxidation product of ABTS at 415 nm, manganese(II) in the range 0.05–1.0 ng ml⁻¹ can be determined with a sampling frequency of 30 h⁻¹. A relative standard deviation (R.S.D.) (n=10) is 1.6% at the 0.5 ng ml⁻¹ level. The proposed method suffers from few interferences and has been successfully applied to the determination of manganese in river, lake and seashore water samples.