试验制备了一种荧光试剂5,10,15-三苯基-20-吡啶基卟啉(TPPyP),该试剂激发光谱(λex)为420 nm时,在650 nm波长处有发射光谱(λem)峰。当试剂与铅(Ⅱ)反应时产生荧光猝灭现象。提出了以此试剂为荧光探针测定痕量铅(Ⅱ)的荧光光度法。在邻苯二甲酸盐-盐酸缓冲溶液中,一定量的十六烷基三甲基溴化铵(CTMAB)存在下,通过测定样品溶液和空白溶液在发射波长650 nm的荧光强度,计算得反应液荧光强度的降低程度ΔF;结果表明:ΔF值与铅(Ⅱ)的质量浓度在1.0×10-4~1.5×10-3mg·L-1范围内呈线性关系,方法的检出限(3s/k)为4.0×10-5mg·L-1。此方法用于膨化食品中铅(Ⅱ)的测定,回收率在95.0%~107.0%之间,相对标准偏差(n=6)小于3%。

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%.