Coplen Tyler B, Qi Haiping
U.S Geological Survey, 431 National Center, Reston, VA 20192, USA.
U.S Geological Survey, 431 National Center, Reston, VA 20192, USA.
Forensic Sci Int. 2016 Sep;266:222-225. doi: 10.1016/j.forsciint.2016.05.029. Epub 2016 Jun 3.
The hydrogen isotopic composition (δ(2)HVSMOW-SLAP) of USGS42 and USGS43 human hair stable isotopic reference materials, normalized to the VSMOW (Vienna-Standard Mean Ocean Water)-SLAP (Standard Light Antarctic Precipitation) scale, was originally determined with a high temperature conversion technique using an elemental analyzer (TC/EA) with a glassy carbon tube and glassy carbon filling and analysis by isotope-ratio mass spectrometer (IRMS). However, the TC/EA IRMS method can produce inaccurate δ(2)HVSMOW-SLAP results when analyzing nitrogen-bearing organic substances owing to the formation of hydrogen cyanide (HCN), leading to non-quantitative conversion of a sample into molecular hydrogen (H2) for IRMS analysis. A single-oven, chromium-filled, elemental analyzer (Cr-EA) coupled to an IRMS substantially improves the measurement quality and reliability of hydrogen isotopic analysis of hydrogen- and nitrogen-bearing organic material because hot chromium scavenges all reactive elements except hydrogen. USGS42 and USGS43 human hair isotopic reference materials have been analyzed with the Cr-EA IRMS method, and the δ(2)HVSMOW-SLAP values of their non-exchangeable hydrogen fractions have been revised: [Formula: see text] [Formula: see text] where mUr=0.001=‰. On average, these revised δ(2)HVSMOW-SLAP values are 5.7mUr more positive than those previously measured. It is critical that readers pay attention to the δ(2)HVSMOW-SLAP of isotopic reference materials in publications as they may need to adjust the δ(2)HVSMOW-SLAP measurement results of human hair in previous publications to ensure all results are on the same isotope-delta scale.
美国地质调查局（USGS）42号和43号人发稳定同位素参考物质的氢同位素组成（δ(2)HVSMOW - SLAP），归一化至VSMOW（维也纳标准平均海水）- SLAP（标准轻南极降水）标度，最初是使用配备玻璃碳管和玻璃碳填充物的元素分析仪（TC/EA）通过高温转换技术测定的，并通过同位素比率质谱仪（IRMS）进行分析。然而，当分析含氮有机物质时，TC/EA IRMS方法可能会产生不准确的δ(2)HVSMOW - SLAP结果，因为会形成氰化氢（HCN），导致样品无法定量转化为用于IRMS分析的分子氢（H2）。与IRMS联用的单炉、填充铬的元素分析仪（Cr - EA）极大地提高了含氢和含氮有机材料氢同位素分析的测量质量和可靠性，因为热铬会清除除氢以外的所有活性元素。已使用Cr - EA IRMS方法分析了USGS42号和43号人发同位素参考物质，其不可交换氢组分的δ(2)HVSMOW - SLAP值已得到修正：[公式：见原文][公式：见原文]，其中mUr = 0.001 =‰。平均而言，这些修正后的δ(2)HVSMOW - SLAP值比之前测量的值正5.7mUr。读者务必注意出版物中同位素参考物质的δ(2)HVSMOW - SLAP，因为他们可能需要调整先前出版物中人发的δ(2)HVSMOW - SLAP测量结果，以确保所有结果处于相同的同位素δ标度上。
