BACKGROUND Due to the biogeochemical fractionation of isotopes, organic material can be heterogeneous at the microscale. Because this heterogentiy preserves in the rock record, the microscale measurement of carbon isotopes is an important frontier of geobiology. Such analyses via secondary ion mass spectrometry (SIMS) have been, however, held back by the lack of an appropriate homogeneous synthetic standard that can be shared between laboratories. Such a standard would need to yield a carbon signal intensity within the same instrument dynamic range as that found for typical rocks, exhibit minimal matrix effects under typical SIMS conditions, and be widely available. In this work, five possible standards were tested with repeated δ(13)C ion microprobe measurements against the PPRG #215-1 Precambrian chert that has been used as a working standard for these types of analyses by several laboratories. RESULTS Results showed that silica powder, pressed, and bonded with Ceramacast 905 produced a useful synthetic standard. The material produced has a secondary ion carbon yield of only about 15× that of the PPRG #215-1 organic-rich chert. Finally, the material, once dried sufficiently, did not demonstrate an observable matrix effect when the carbon isotopes were measured. Another similar material (silica nanopowder, pressed, and bonded with Aremco-Bond 526N) appears to have retained its hydration after a substantial effect to dry it. The isotopes measurements of this more hydrated material showed a significant matrix effect that was diminished by intense pre-sputtering. The results indicate water can affect SIMS carbon isotopic measurements, and an intense beam reduces the effect. A hydrated standard might be useful to monitor the effect. CONCLUSIONS A suitable artificial standard for SIMS isotopic measurements of organic material in rocks has been found, and it will allow an acute growth in both the quantity and quality of studies of ancient carbon at the microscale. Also, this work has revealed a novel water-associated matrix effect for carbon isotopes. This newly revealed matrix effect is important because it might have misled previous research. The effect could lead to increased observed heterogeneity of partially hydrated samples and/or produced systematic differences between natural targets and the standards used.

中文翻译：

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用于分析硅酸盐中碳的碳同位素以及观察到明显的水相关基质效应的合成标准。

背景技术由于同位素的生物地球化学分馏，有机材料在微观尺度上可能是异质的。由于这种异质性保留在岩石记录中，因此碳同位素的微观测量是地球生物学的重要前沿。但是，由于缺乏适当的均质合成标准品，实验室之间无法共享，因此无法通过二次离子质谱（SIMS）进行此类分析。这样的标准需要在与典型岩石相同的仪器动态范围内产生碳信号强度，在典型的SIMS条件下表现出最小的基体效应，并且可以广泛使用。在这项工作中，针对PPRG＃215-1前寒武纪br石，通过重复进行δ（13）C离子微探针测试，测试了五种可能的标准物，该试验已被多个实验室用作这类分析的工作标准。结果结果表明，经压制并与Ceramacast 905粘合的二氧化硅粉末产生了有用的合成标准品。所生产的材料具有的二次离子碳收率仅为PPRG＃215-1富含有机organic石的二次离子碳收率的15倍。最后，该材料一旦充分干燥，在测量碳同位素时就不会表现出可观察到的基体效应。另一种类似的材料（二氧化硅纳米粉，经压制并与Aremco-Bond 526N粘合）在干燥后具有明显的水化作用。对这种水合程度更高的材料进行的同位素测量显示出显着的基质效应，而强烈的预溅射使基质效应减弱了。结果表明，水会影响SIMS碳同位素测量，强烈的光束会降低这种影响。水合标样可能对监测效果有用。结论已经找到了适用于SIMS同位素测量岩石中有机物的合适的人工标准，这将使微观上古代碳研究的数量和质量都得到急剧增长。此外，这项工作还揭示了碳同位素的新型水相关基质效应。这种新发现的基质效应很重要，因为它可能会误导先前的研究。