Application of a modified catalytic effect: determination of nanogram amounts of zinc in milk samples using a kinetic-fluorimetric method

Abstract

An indirect kinetic fluorimetric method for the determination of trace amounts of zinc(II) is described, which is based on its activator effect on the oxidation of 2-hydroxybenzaldehyde thiosemicarbazone by hydrogen peroxide catalysed by managanese(II). The reaction is followed by measuring the rate of appearance of the fluorescence of the oxidation product (λ_exc.= 365 nm and λ_em.= 440 nm). The calibration graph is linear in the range 50–400 ng ml^–1 of zinc (accuracy ±2.0%). The proposed method suffers from very few interferences and has been applied satisfactorily to the determination of zinc in several commercially available milk samples.