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4~500 μg·L-1范围内与其峰高呈线性关系,检出限(3S/N)为1 μg·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 (HNO3 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 Pb2+ 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 Pb2+ solution.Linear relationship between values of the peak height and mass concentration of Pb2+ was obtained in the range of 4-500 μg·L-1,with its detection limit (3S/N) of 1 μg·L-1.