铅-二甲酚橙络合吸附波及食糖中铅的测定

STUDIES ON THE COMPLEX WAVE OF LEAD-XYLENOL ORANGE AMD DETERMINATION OF LEAD IN SUGARS

铅-二甲酚橙(XO)络合物的极谱行为的研究迄今尚未报导过.XO在0.025mol/L(NH_4)_2SO_4,0.1mol/L六次甲基四胺的溶液(pH5.0)中,出现一还原波,Ep_1=-0.64V(vs.SCE).再加入微量的Pb(Ⅱ)后,在较正的电位上出现一灵敏的还原波,Ep_2=-0.44V,ip与CPb(II)在5×10^(-8)—2×10^(_6)mo1l/L范围内成线性关系,并用于食糖中微量铅的测定,方法简便,可靠.用等摩尔连续变化法确定络合物的络合比为1:1.用单扫示波极谱、循环伏安法、常规脉冲极谱等研究极谱波的性质及其机理.实验证明.该波为络合吸附波.

This paper reports the polarographic behavior of lead-xylenol orange(XO)complex. In a supporting electrolyte containing 0.025mol/L(NH4)2SO4 and 0.1mol/L hexamine (pH5.0), a sensitive Wave of lead-XO has been obtained by using linear sweep voltammetry. The peak potential is 0.44V(vs.SCE). The change of peak height with the concentration of lead is linear in the range from 5×10-8 to 2×10-8mol/L, and the method described is applicable to the determination of lead in sugars. In the Solution, the composition of the complex has been determined to be 1:1. The wave has been proved to be an adsorptive wave by several experiments.