Determination of Osmium Concentrations and 187Os/188Os of Crude Oils and Source Rocks by Coupling High-Pressure, High-Temperature Digestion with Sparging OsO4 into a M

详细信息    查看全文

• 作者：Indra S. Sen ; Bernhard Peucker-Ehrenbrink
• 刊名：Analytical Chemistry
• 出版年：2014
• 出版时间：March 18, 2014
• 年：2014
• 卷：86
• 期：6
• 页码：2982-2988
• 全文大小：307K
• 年卷期：v.86,no.6(March 18, 2014)
• ISSN：1520-6882

文摘

The ¹⁸⁷Os/¹⁸⁸Os ratio that is based on the 尾^{鈥?/sup>-decay of 187Re to 187Os (t_1/2 = 41.6 billion years) is widely used to investigate petroleum system processes. Despite its broad applicability to studies of hydrocarbon deposits worldwide, a suitable matrix-matched reference material for Os analysis does not exist. In this study, a method that enables Os isotope measurement of crude oil with in-line Os separation and purification from the sample matrix is proposed. The method to analyze Os concentration and 187Os/187Os involves sample digestion under high pressure and high temperature using a high pressure asher (HPA-S, Anton Paar), sparging of volatile osmium tetroxide from the sample solution, and measurements using multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). This methods significantly reduced the total procedural time compared to conventional Carius tube digestion followed by Os separation and purification using solvent extraction, microdistillation and N-TIMS analysis. The method yields Os concentration (28 卤 4 pg g鈥?) and 187Os/188Os (1.62 卤 0.15) of commercially available crude oil reference material NIST 8505 (1 S.D., n = 6). The reference material NIST 8505 is homogeneous with respect to Os concentration at a test portion size of 0.2 g. Therefore, 187Os/188Os composition and Os concentration of NIST 8505 can serve as a matrix-matched reference material for Os analysis. Data quality was assessed by repeated measurements of the USGS shale reference material SCo-1 (sample matrix similar to petroleum source rock) and the widely used Liquid Os Standard solution (LOsSt). The within-laboratory reproducibility of 187Os/188Os for a 5 pg of LOsSt solution, analyzed with this method over a period of 12 months was 1.4% (1 S.D., n = 26), respectively.}