Spectrofluorimetric determination of traces of zinc with the cadmium—α,β,γ,δ-tetrakis(4-sulphophenyl) - porphine complex

Abstract

A highly sensitive spectrofluorimetric method for the determination of zinc was established by using the metal ion substitution reaction of the cadmium—α,β,γ,δ-tetrakis(4-sulphophenyl)porphine (H2P4−) complex with zinc ion. The zinc complex, ZnP4−, was quantitatively formed within 3 min at room temperature in the pH range 10–11. The relative fluorescence intensity ratio, F(ZnP4−)/F(CdP4−), was 37.0 at λ(em) = 604 nm [λ(ex) = 422 nm]. The calibration graph was linear over the concentration range 5–100 ng Zn2+ ml−1 in sample solution. The detection limit (signal-to-noise ratio = 3) was 0.15 ng Zn2+ ml−1 and the relative standard deviation was 1.39% for 16.6 ng Zn2+ ml−1 (ten determinations). Results are given for the application of the method to the determination of Zn2+ in tap water.