SPECTROFLUOROMETRIC DETERMINATION OF TRACES OF ZINC WITH THE CADMIUM-ALPHA,BETA,GAMMA,DELTA-TETRAKIS(4-SULFOPHENYL)-PORPHINE COMPLEX

A highly sensitive spectrofluorimetric method for the determination of zinc was established by using the metal ion substitution reaction of the cadmium-alpha,beta,gamma,delta-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 lambda(em) = 604 nm [lambda(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.