Catalytic fluorimetric determination of nanogram amounts of lead in plastic containers for food by oxidation of pyridoxal 2-pyridylhydrazone with hydrogen peroxide

Abstract

A kinetic fluorimetric method for the determination of trace amounts of lead(II) is described. It is based on the catalytic action of this ion in the oxidation of pyridoxal 2-pyridylhydrazone by hydrogen peroxide, which yields a product exhibiting an intense blue fluorescence in basic solution (λ_ex.= 355, λ_em.= 425 nm). The kinetics of the chemical reaction are followed by the fluorescence intensity versus time graphs. Using several kinetic methods (tangent, fixed-time and fixed-intensity), Pb(II) at the 0.05–0.40 µg ml^–1 level can be determined. The proposed method suffers few interferences and has been applied satisfactorily to the determination of lead in plastic containers for food.