报道了对多波长K系数-分光光度法同时测定食品中锌及铅的改进方法.采用5-Br-PADAP作为显色剂,Triton X-100作为增溶剂,在pH 9.2的氨性缓冲溶液中进行锌(Ⅱ)及铅(Ⅱ)与5-Br-PADAP的显色反应,采用不加显色剂的空白溶液作为参比溶液,除了显色剂在测量波长区间的吸收所引起的误差.测定锌(Ⅱ)时,选用的波长为558 nm,参比波长为572 nm及446 nm;测定铅(Ⅱ)时,测定波长为572 nm,而参比波长为558 nm及446 nm,两元素的线性范围均为(1.0~20.0 μg)/25 mL.应用此方法测定了味精和松花皮蛋两种样品中的锌量和铅量,所得测定值与原子吸收光谱法的测定结果相符.在此样品的基础上,加入锌及铅的标准溶液作回收试验,测得锌及铅的回收率依次在96.5%~104.2%之间和95.0%~103.7%之间.

An improved method of multiwavelength K-Factor-spectrophotometric determination of zinc and lead in food,using 5-Br-PADAP as chromogenic reagent and Trion X-100 as solubilizing agent,was reported in this paper.Error due to the absorption of 5-Br-PADAP in the measuring wavelength region was eliminated by using a reference solution of the blank solution without addition of chromogenic reagent.The color reaction for both zinc and lead with 5-Br-PADAP was carried out in an ammoniacal buffer solution of pH 9.2.In the determination of zinc,558 nm was chosen as the measuring wavelength,and 572 nm,446 nm were chosen as the reference wavelengths,while in the determination of lead,the measuring wavelength and reference wavelengths chosen were 572 nm and 558 nm,446 nm respectively.Linearity for both elements were in the range of 1.0 to 20.0 μg per 25 mL of testing solution.Zinc and lead in samples of gourmet powder and preserved egg were determined by the proposed method giving results in consistency with the results obtained by AAS.Based on these samples,standard solutions of Zn2+ and Pb2+ were added and tests for recovery were performed,results obtained were in the ranges of 96.5%-104.2% for Zn and 95.0%-103.7% for Pb.