This paper is dealing with the effects the addition of H₂O or O₂ to He aerosol carrier gas has on ²⁰⁶Pb/²³⁸U ratios during laser ablation inductively-coupled plasma mass spectrometry (LA-ICPMS) of natural zircons and synthetic silicate glass. The following parameters were studied: (i) system bias defined as constant but LA-ICPMS system-dependent shifts in ²⁰⁶Pb/²³⁸U ratios, (ii) down-hole fractionation given by the slope of ²⁰⁶Pb/²³⁸U ratio vs. LA time, and (iii) the sum of (i) and (ii) referred to as overall elemental fractionation. To isolate and study changes of ²⁰⁶Pb/²³⁸U ratios arising independently from either LA sampling or ICPMS analysis of the generated aerosols, a diffusion-based gas exchange device was used. The supply of He + O₂ caused relative changes in mean ²⁰⁶Pb/²³⁸U values and temporal gradients due to the LA process of less than 40 %. By contrast, addition of H₂O to the He carrier gas changed ²⁰⁶Pb/²³⁸U ratios by up to 150 % through processes occurring during LA sampling as well as ICPMS analysis. Here, opposing temporal gradients of ²⁰⁶Pb/²³⁸U ratios canceled out at relative humidity levels close to the ambient saturation vapor pressure. As a consequence, changes in ²⁰⁶Pb/²³⁸U ratios caused by down-hole fractionation could be suppressed. However, the admixture of H₂O also affected the system bias at the same time, resulting in increased offsets in ²⁰⁶Pb/²³⁸U ratios such that the accuracy of LA-ICPMS analyses worsened by up to 6 % when applied to the age determination of zircons. Neither worsening nor significant improvements in the accuracy of ²⁰⁶Pb/²³⁸U-based ages were observed in the case of LA-ICPMS using He + O₂ carrier gas mixtures.

中文翻译：

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含H ₂ O和O ₂的He载气对锆石LA-ICPMS中²⁰⁶ Pb / ²³⁸ U系统偏压和井下分离的影响

本文研究了在天然锆石和合成硅酸盐玻璃的激光烧蚀电感耦合等离子体质谱法（LA-ICPMS）中，向He气溶胶载气中添加H ₂ O或O ₂对²⁰⁶ Pb / ²³⁸ U比的影响。研究了以下参数：（i）系统偏差定义为²⁰⁶ Pb / ²³⁸ U比值恒定但与LA-ICPMS相关的系统偏移；（ii）²⁰⁶ Pb / ²³⁸ U比值的斜率vs. LA时间，以及（iii）（i）和（ii）之和称为总元素分级。分离和研究²⁰⁶ Pb / ^238的变化U比率独立于产生的气溶胶的LA采样或ICPMS分析而产生，使用了基于扩散的气体交换装置。He + O ₂的供给由于LA过程小于40％，导致平均²⁰⁶ Pb / ²³⁸ U值和时间梯度的相对变化。相比之下，通过在LA采样以及ICPMS分析中发生的过程，向He载气中添加H ₂ O最多可将²⁰⁶ Pb / ²³⁸ U比值改变150％。在此，相对湿度为²⁰⁶ Pb / ²³⁸ U的相对时间梯度在接近环境饱和蒸汽压的相对湿度下被抵消。结果是^206的变化井下分级所引起的Pb / ²³⁸ U比可以得到抑制。但是，H ₂ O的混合物也同时影响了系统偏差，导致²⁰⁶ Pb / ²³⁸ U比值的偏移增加，因此，将LA-ICPMS分析的准确性应用于年龄确定时，恶化了多达6％。的锆石。在使用He + O ₂载气混合物的LA-ICPMS的情况下，未观察到²⁰⁶ Pb / ²³⁸ U基年龄的准确性恶化或明显改善。