Analyte- and matrix-dependent elemental response variations in laser ablation inductively coupled plasma mass spectrometry
Analyte- and matrix-dependent elemental response variations in laser ablation inductively coupled plasma mass spectrometry
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DOI：
10.1039/b205547c
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发表时间：
2002-09
影响因子：
3.4
通讯作者：
I. Rodushkin;M. Axelsson;D. Malinovsky;D. Baxter
中科院分区：
文献类型：
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作者：
I. Rodushkin;M. Axelsson;D. Malinovsky;D. Baxter
鉴于激光烧蚀电感耦合等离子体质谱 (LA-ICP-MS) 有可能直接测定固体样品中约 80 种元素的浓度，但大多数应用仅限于相当少量的分析物，这一事实表明校准存在固有问题。这些源于任何给定样品中的分析物之间以及任何给定分析物的基质之间的元素响应变化。尽管响应变化通常归因于消融或传输效率的差异，但也有迹象表明 ICP 中可能会发生某种程度的元素分馏。目前的研究结果表明，ICP 是分馏的主要来源，因此响应变化与元素及其主体颗粒的热力学性质有关。通过研究 16 个基质中分析物响应与载气流速的关系（所谓的流速图），可以清楚地辨别 LA-ICP-MS 中元素的行为模式并用于分类。从这些研究中鉴定出三组元素在所有基质上表现出一致的行为模式：A组，包含具有高氧化物键解离焓的难熔元素； B组，包括稀有和较重的碱土元素（Ca、Sr、Ba）； C组，由挥发性或低质量元素组成。由于每组都表现出明显不同的最佳流速和流速图形状（除 C 组元素外），这些形状也取决于基质，因此 LA-ICP-MS 在多元素分析中的实用性受到严重影响。事实上，多种分析物的定量测定要求为每组中的至少一种元素以及不能令人满意地分类的所有元素建立校准因子。该分类可作为选择合适的 LA-ICP-MS 内标的指南，至少对于某些分析物组而言是如此。还给出了示例，显示如何使用流速图来预测所选内标或固体标准材料用于校准的充分性。
Given that laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has the potential to directly determine the concentrations of some 80 elements in solid samples, the fact that most applications are limited to considerably smaller numbers of analytes is indicative of the inherent problems with calibration. These stem from elemental response variations, both between analytes in any given sample and between matrices for any given analyte. Although response variations are often attributed to differences in ablation or transport efficiencies, there have also been indications that some degree of elemental fractionation may occur in the ICP. The results of the present investigations demonstrate that the ICP is the predominant source of fractionation, and thus response variations are related to the thermodynamic properties of the elements and their host particles. By studying analyte response as a function of carrier gas flow rate (so called flow rate plots) in 16 matrices, patterns in the behaviour of the elements in LA-ICP-MS could be clearly discerned and used for classification. Three groups of elements displaying consistent behavioural patterns over all matrices were identified from these studies: Group A, comprising refractory elements with high oxide bond dissociation enthalpies; Group B, including the rare and heavier alkaline earth (Ca, Sr, Ba) elements; and Group C, consisting of volatile or low mass elements. As each group exhibits decidedly different optimum flow rates and flow rate plot shapes which, with the exception of the group C elements, also depend on the matrix, the utility of LA-ICP-MS for multi-element analyses is severely compromised. In fact, quantitative determination of a wide range of analytes demands that calibration factors be established for at least one element from each group, as well as for all elements that could not be satisfactorily classified. This classification may serve as a guide in the selection of suitable internal standards for LA-ICP-MS, at least for certain groups of analytes. Examples are also given showing how flow rate plots can be employed to predict the adequacy of selected internal standards or solid standard materials for calibration.