微分电位溶出法测定涂料中痕量铅

Determination of Trace Amount of Lead in Paint by Differential Potentiometric Stripping Analysis

涂料样品1份置于瓷坩埚中,于105℃烘干除去有机溶剂,加热炭化并在475～500℃灼烧1 h后,残渣溶于稀硝酸中供微分电位溶出法测定用。在含有1 mol·L^(-1)硝酸钾、pH 0.5的酸性介质中,工作电极施加上-1.10 V还原电位,40 s使铅在汞膜旋转园盘玻碳电极上还原并汞齐化。在氧化剂作用下,使富集在工作电极上的铅汞齐重新脱溶下来,并记录-0.10～-0.90 V之间的微分电位溶出曲线,铅离子的溶出峰电位为-0.46 V(vs.SCE),采用标准曲线法计算求得样品中铅含量。铅的质量浓度在4～500μg·L^(-1)范围内与其峰高呈线性关系,检出限(3S/N)为1μg·L^(-1)。

The paint sample in a porcelain crucible was first dried in an oven at 105℃to expel organic solvents,then charred by heating on a hot plate and finally ignited in a muffle furnace at 475-500℃for 1 h.The residue was dissolved in dil.HNO3,and used for the differential potentiometric stripping analysis.Lead ion in the sample solution（HNO_3 medium of pH 0.5,containing 1 mol·L^-1 KNO3 ） was reduced and amalgamated at the Hg-film-rotary glassy carbon disk electrode at the potential of - 1.10 V（vs.SCE） for 40 s.Lead ion was then stripped from the working electrode by the action of oxidant and the differential stripping potential curve in the potential range of -0.10- - 0.90 V was recorded and the stripping potential peak of Pb^2＋ was observed at -0.46 V（vs.SCE）.Content of lead in the sample was found from a working curve perpared in the same way with standard Pb^2＋ solution.Linear relationship between values of the peak height and mass concentration of Pb^2＋ was obtained in the range of 4-500μg·L^-1,with its detection limit（3S/N） of 1μg·L^-1.