Increased demand for improving ultra-low background detection capabilities for rare-event fundamental physics applications has resulted in the need for fast, convenient and clean assay methodologies that either preclude or reduce chemical sample pre-processing. A novel method for the measurement of ultra-trace concentrations (fg g⁻¹ level) of natural ²³²Th and ²³⁸U and non-natural tracer isotopes ²²⁹Th and ²³³U was demonstrated in a solution of 10 μg g⁻¹ each of Au, Pt, Ir, and W in 2% HNO₃ using an ICP-QQQ-MS. Polyatomic interference across an m/z range of 227–239 was characterized: the major interferent with ²²⁹Th⁺ is ¹⁹⁴Pt³⁵Cl⁺; interferents with ²³²Th⁺ are ¹⁸⁴W¹⁶O₃⁺, ¹⁸³W¹⁶O₃H⁺, ¹⁹²Pt⁴⁰Ar⁺, ¹⁹⁶Pt³⁶Ar⁺, ¹⁹⁵Pt³⁷Cl⁺, and ¹⁹⁷Au³⁵Cl⁺; those with ²³³U⁺ are ¹⁹³Ir⁴⁰Ar⁺, ¹⁹⁷Au³⁶Ar⁺, and ¹⁸⁴W¹⁶O₃H⁺; and that with ²³⁸U⁺ is ¹⁹⁸Pt⁴⁰Ar⁺. Scanning the selected m/z range of 227–270 showed that higher oxide polyatomic species from the matrix elements either did not form or did not create a significant background on the target analyte masses. All measured concentrations in standard solutions matched the target values within the 98% confidence interval. The Th measurements were 80% accurate or better at the 10 fg g⁻¹ level and above, and the U measurements were 90% accurate or better at the 10 fg g⁻¹ level and above. Measurements at the 1 fg g⁻¹ level were consistent with target values within 1 standard deviation, although the standard deviations of all three replicates were greater than 20% of the measured concentration value. Method detection limits in the matrix solutions were calculated to be 2.74 fg Th and 12.9 fg U. In an electronic sample, which typically has 0.1% precious metal content, our method would give detection limits of 274 fg Th and 1291 fg U given a maximum of 10 μg g⁻¹ coinage metal matrix. This method is but one example of how state-of-the-art quadrupole mass spectrometry and collision reaction cell technology can be leveraged to develop novel analytical capability at ultra-trace levels.

中文翻译：

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使用O2反应气体的ICP-MS / MS来测量Au，Pt，Ir和W矩阵中的痕量U和Th的新方法

对用于稀有事件基本物理学应用的超低本底检测功能的需求日益增长，导致需要一种快速，便捷和清洁的测定方法，以防止或减少化学样品的预处理。在10μgg ^-1的Au溶液中证明了一种测量天然²³² Th和²³⁸ U以及非天然示踪同位素²²⁹ Th和²³³ U的超痕量浓度（fg g ^-1水平）的新方法ICP-MS / MS测定2％HNO ₃中的Pt，Ir和W 跨m / z的多原子干扰227-239范围的特征是：²²⁹ Th ⁺的主要干扰物是¹⁹⁴ Pt ³⁵ Cl ⁺；²³² Th ^+的干扰物为¹⁸⁴ W ¹⁶ O ₃ ⁺，¹⁸³ W ¹⁶ O ₃ H ⁺，¹⁹² Pt ⁴⁰ Ar ⁺，¹⁹⁶ Pt ³⁶ Ar ⁺，¹⁹⁵ Pt ³⁷ Cl ⁺和¹⁹⁷ Au ³⁵Cl ⁺ ; 那些具有²³³ Ü ⁺是¹⁹³的Ir ⁴⁰的Ar ⁺，¹⁹⁷的Au ³⁶的Ar ⁺，和¹⁸⁴ w ^ ¹⁶ ö ₃ ħ ⁺ ; 和与²³⁸ Ü ⁺是¹⁹⁸的Pt ⁴⁰的Ar ⁺。扫描所选的m / z227-270的范围表明，基质元素中较高的氧化物多原子种类未形成或未在目标分析物质量上产生明显的背景。标准溶液中所有测得的浓度均在98％的置信区间内与目标值匹配。对TH的测量分别为80％的准确或更好在10 FG克^-1级以上，并且U的测量分别为90％的准确或更好在10 FG克^-1级以上。在1 fg g ^-1下的测量尽管所有三个重复样品的标准偏差均大于测量浓度值的20％，但该水平与1个标准偏差内的目标值一致。计算得出的基质溶液中方法的检出限为2.74 fg Th和12.9 fgU。在通常具有0.1％贵金属含量的电子样品中，我们的方法给出的最大检出限为274 fg Th和1291 fg U 10μgg ^-1造币金属基质。这种方法只是如何利用最新的四极杆质谱和碰撞反应池技术来开发超痕量分析水平的一种示例。