Dual-indicator reaction spectrophotometry for the determination of trace manganese with Mn(II)-brillant green-PAN catalytic system

A new dual-wavelength dual-indicator catalytic kinetic spectrophotometric method for the determination of manganese was studied.The method is based on the catalytic effect of trace activated manganese(Ⅱ) on the oxidation of brilliant green and 1-(2-pyridylazo)-2-naphthol by patassium periodate in Na2HPO4-KH2PO4 medium.The absorbance was measured at 630 nm and 430 nm.The difference of absorbance between catalytic and non-catalytic system was obtained.Manganese(Ⅱ) concentration was linear with the sum of the absorbance difference.The linear range for the determination of manganese is 0.000 10-0.005 0 μg/mL and the detection limit is 2.4×10-11 g/mL.This method has been successively applied in the determination of trace manganese in water,giving the addition standard recoveries from 96.9% to 101.6% and the RSD up to 2.0%.