This paper deals 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 zircon 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 the ²⁰⁶Pb/²³⁸U ratio vs. LA time, and (iii) the sum of (i) and (ii) referred to as the 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 as well as ICPMS analysis. Here, the opposing temporal gradients of ²⁰⁶Pb/²³⁸U ratios canceled out at relative humidity levels close to the saturation vapor pressure under ambient lab conditions, i.e., 20 °C room temperature. 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 zircon. Neither worsening nor significant improvements in the accuracy of ²⁰⁶Pb/²³⁸U 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系统偏压和井下分馏的影响

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相关的系统位移；（ii）²⁰⁶ Pb / ²³⁸ U比值的斜率给出的井下馏分与。 LA时间，和（iii）的总和（ⅰ）和（ii）被称为整体元素分馏。为了隔离和研究独立于LA采样或生成气溶胶的ICPMS分析而引起的²⁰⁶ Pb / ²³⁸ U比值的变化，使用了基于扩散的气体交换设备。He + O ₂的供给导致平均²⁰⁶ Pb / ²³⁸ U值和时间梯度的相对变化，这是因为LA过程的变化小于40％。相比之下，通过在LA期间发生的过程以及ICPMS分析，向He载气中添加H ₂ O最多可将²⁰⁶ Pb / ²³⁸ U的比率改变150％。在这里，相对的时间梯度为²⁰⁶ Pb / ²³⁸在环境实验室条件（即室温20°C）下，相对湿度水平接近饱和蒸气压时，U比率被抵消。结果，可以抑制由于井下分级而引起的²⁰⁶ Pb / ²³⁸ U比的变化。但是，H ₂ O的混合物同时也影响系统偏差，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，精度降低了6％。锆石 在使用He + O的LA-ICPMS的情况下，未观察到²⁰⁶ Pb / ²³⁸ U年龄准确性的恶化或显着提高。_2种载气混合物。