Spectrofluorimetric determination of manganese at the nanogram level by catalytic oxidation of 2-hydroxy-1-naphthaldehyde salicyloylhydrazone by hydrogen peroxide

A new fluorescent reagent, 2-hydroxy-1-naphthaldehyde salicyloylhydrazone ( HNSH), was synthesized and its ionization constants were established spectr ophotometrically. The fluorescent reaction of this reagent with hydrogen pe roxide, catalysed by Mn(II), was studied. Based on this oxidation reaction, a spectrofluorimetric method was developed for the determination of mangan ese in a water-ethanol (5.5 + 4.5, v/v) medium at pH 10.90. Under these con ditions, the oxidation reaction was followed by measuring the change rate o f fluorescence (lambda ex = 300 and lambda em = 408 nm). The linear range o f the method is from 0.0 to 50 ng ml(-1) with a precision of +/- 1.0% and t he detection limit is 0.97 ng ml(-1) of manganese when a fixed-time method is used in the assay. Interferences of other ions were studied. The method has been successfully applied to the determination of manganese in human ha ir. wheat powder, lake water and tap water.