Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Oviedo, Spain.
Anal Bioanal Chem. 2012 Jan;402(1):269-75. doi: 10.1007/s00216-011-5420-6. Epub 2011 Oct 8.
The determination of trace elements in oil samples and their products is of high interest as their presence significantly affects refinery processes and the environment by possible impact of their combustion products. In this context, inductively coupled plasma mass spectrometry (ICP-MS) plays an important role due to its outstanding analytical properties in the quantification of trace elements. In this work, we present the accurate and precise determination of selected heavy metals in oil samples by making use of the combination of μ-flow direct injection and isotope dilution ICP-MS (ICP-IDMS). Spike solutions of (62)Ni, (97)Mo, (117)Sn and (206)Pb were prepared in an organic solvent, mixed directly with the diluted oil samples and tested to be fit for purpose for the intended ID approach. The analysis of real samples revealed strong matrix effects affecting the ICP-MS sensitivity, but not the isotope ratio measurements, so that accurate results are obtained by ICP-IDMS. Typical relative standard deviations were about 15% for peak area and peak height measurements, whereas the isotope ratios were not significantly affected (RSD < 2%). The developed method was validated by the analysis of a metallo-organic multi-element standard (SCP-21, typically applied as a calibration standard) and the standard reference material SRM1084a (wear metals in lubricating oil). The obtained results were in excellent agreement with the certified values (recoveries between 98% and 102%), so the proposed methodology of combining μ-flow direct injection and ICP-IDMS can be regarded as a new tool for the matrix-independent, multi-element and reliable determination of trace elements in oil and related organic liquids.
油样及其产品中微量元素的测定具有重要意义，因为它们的存在会通过燃烧产物对炼油过程和环境产生重大影响。在这种情况下，电感耦合等离子体质谱（ICP-MS）由于其在痕量元素定量分析方面的出色分析性能而具有重要作用。在这项工作中，我们通过利用微流直接进样和同位素稀释 ICP-MS（ICP-IDMS）相结合，准确、精确地测定了油样中的选定重金属。（62）Ni、（97）Mo、（117）Sn 和（206）Pb 的混合标准溶液用有机溶剂制备，直接与稀释后的油样混合，经测试适合预期的 ID 方法。对实际样品的分析表明，强烈的基质效应会影响 ICP-MS 的灵敏度，但不会影响同位素比值的测量，因此 ICP-IDMS 可以获得准确的结果。峰面积和峰高测量的典型相对标准偏差约为 15%，而同位素比值则没有受到显著影响（RSD < 2%）。通过对金属有机多元素标准品（通常用作校准标准的 SCP-21）和标准参考物质 SRM1084a（润滑油中的磨损金属）的分析验证了所开发方法的准确性。所得结果与认证值（回收率在 98%至 102%之间）非常吻合，因此，将微流直接进样与 ICP-IDMS 相结合的方法可以被视为一种新的工具，用于在不依赖基质的情况下、对油和相关有机液体中的痕量元素进行多元素和可靠的测定。
