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将193nm准分子纳秒激光与四级杆电感耦合等离子体质谱联用,测量了国际参照物玻璃中Pb同位素丰度比。通过剥蚀NIST612,USGS和MPI-DING玻璃,探讨了利用激光剥蚀电感耦合等离子体质谱直接测定固体样品铅同位素比值的精密度及其适用范围。通过扣除Ar载气中204Hg对204Pb的同量异位素干扰,采用内标法和外标法校正LA-ICP-MS仪器的质量歧视效应,获得的206Pb/204Pb、207Pb/204Pb、208Pb/204Pb同位素比值测量的相对误差小于±1.2%,207Pb/206Pb、208Pb/206Pb同位素比值测定的相对误差小于±0.8%。对比结果表明,采用内标法校正的结果更接近真实值。测定的Pb同位素比值的精密度与样品中Pb含量密切相关,对Pb含量大于40μg/g的样品,同位素比值206Pb/204Pb、207Pb/204Pb、208Pb/204Pb的RSD在1.0%以内,207Pb/206Pb、208Pb/206Pb的RSD在0.5%以内。大气颗粒物样品中Pb含量很高,采用LA-ICP-MS测定Pb同位素比值,能够鉴别污染来源,满足示踪的要求。
The 193 nm excimer nanosecond laser was coupled with a quadrupole rod inductively coupled plasma mass spectrometer to measure the abundance ratio of Pb isotope in the international reference glass. By means of denudation of NIST612, USGS and MPI-DING glass, the precision and applicability of direct determination of Pb isotope ratio in solid samples by laser ablation inductively coupled plasma mass spectrometry was discussed. The mass discrimination effect of LA-ICP-MS instrument was corrected by internal standard method and external standard method by deducing isobaric interference of 204Hg to 204Pb in Ar carrier gas. The obtained 206Pb / 204Pb, 207Pb / 204Pb and 208Pb / 204Pb The relative error of the isotope ratio measurement is less than ± 1.2% and the relative error of the 207Pb / 206Pb and 208Pb / 206Pb isotope ratio measurements is less than ± 0.8%. The comparison results show that the result of calibration using the internal standard method is closer to the true value. The precision of the Pb isotope ratio was closely related to the Pb content in the samples. The RSDs of the 206Pb / 204Pb, 207Pb / 204Pb and 208Pb / 204Pb were less than 1.0% and 207Pb / 206Pb for the samples with Pb more than 40μg / g, The RSD of 208Pb / 206Pb is within 0.5%. The Pb content of atmospheric particulate matter is very high. The determination of Pb isotope ratio by LA-ICP-MS can identify the sources of pollution and meet the requirements of tracing.