Fluorimetric determination of sulfite by the co-quenching effect of formaldehyde and sulfite on the fluorescence of tetra-substituted amino aluminum phthalocyanine

Abstract

A spectrofluorimetric determination of sulfite based on the co-quenching effect of sulfite and formaldehyde on the fluorescence of a red-region dye, tetra-substituted amino aluminum phthalocyanine (TAAlPc), is described. The relationship between the fluorescence quenching of TAAlPc and the concentration of sulfite is linear over the concentration range of 8–240 ng ml −1 under optimum conditions. The 3 σ limit of detection is 3 ng ml −1 and the relative standard deviation of six replicate measurements is 3.5% for solution containing a 160 ng ml −1 sulfite. The possible reaction mechanism is also discussed. This method has been successfully applied to the determination of sulfite in VK 3 injections and sugar.