SPECTROFLUORIMETRIC DETERMINATION OF MANGANESE AT THE NANOGRAM LEVEL BY CATALYTIC OXIDATION OF 2-HYDROXY-1NAPHTHALDEHYDE SALICYLOYLHYDRAZONE BY HYDROGEN PEROXIDE

A new fluorescent reagent, 2-hydroxy-1-naphthaldehyde salicyloylhydrazone (HNSH), was synthesized and its ionization constants were established spectrophotometrically. The fluorescent reaction of this reagent with hydrogen peroxide, catalysed by Mn(II), was studied. Based on this oxidation reaction, a spectrofluorimetric method was developed for the determination of manganese in a water-ethanol (5.5+4.5, v/v) medium at pH 10.90. Under these conditions, the oxidation reaction was followed by measuring the change rate of fluorescence (?ex = 300 and ?em = 408 nm). The linear range of the method is from 0.0 to 50 ng ml-1 with a precision of ±1.0% and the 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 hair, wheat powder, lake water and tap water.