Fluorospectrophotometric Determination of Trace Amount of Lead by the Fluorescence Quenching of 5,10,15-Triphenyl-20-Pyridy-Porphyrin

A fluorescence reagent, 5, 10, 15-triphenyl-20-pyridyl-porphyrin (abbreviated as TPPyP) was prepared. It was shown that when taking 420 nm as the excitation wavelength (λex), the reagent, TPPyP, showed its fluorescence emission peak at 650 nm (λem). Fluorescence quenching effect was observed when TPPyP was reacted with Pb(Ⅱ). The use of TPPyP as a fluorescence probe in the determination of trace amount of Pb was studied. In a phthalate-HCl buffer medium, Pb(Ⅱ) was reacted with TPPyP in the presence of CTMAB, the magnitude of decrease in fluorescence intensity (ΔF) of the reaction solution were measured at the wavelength of 650 nm by taking the difference between emission fluorescence intensity of the blank solution and the sample solution. Linear relationship between values of ΔF and mass concentration of Pb(Ⅱ) were found in the range of 1.0×10-4-1.5×10-3mg·L-1, with detection limit (3s/k) of 4.0×10-5mg·L-1. Values of recovery found in the analysis of 2 samples of puffed food, were in the range of 95.0%-107.0% with RSD (n=6) <3%.