Sensitive and selective indirect kinetic spectrophotometric determination of manganese in agricultural samples

Abstract

A method for the indirect kinetic determination of manganese based on its inhibitory effect on the copper(II)-catalysed oxidation of 3-hydroxybenzaldehyde azine by potassium peroxydisulphate in an ethanol-ammonia medium is reported. The reaction is monitored spectrophotometrically at 465 nm (absorption maximum of the oxidation product formed). The calibration graph is linear in the range 0.5–5.0 ng ml^–1 of manganese(II), with a relative standard deviation of 1.5% and a detection limit of 0.13 ng ml^–1. The proposed method is selective and is useful for the determination of manganese in agricultural samples such as soils and wines.