title: A revision in hydrogen isotopic composition of USGS42 and USGS43 human-hair stable isotopic reference materials for forensic science.
abstract: 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.
authors.affiliation: U.S Geological Survey, 431 National Center, Reston, VA 20192, USA. Electronic address: tbcoplen@usgs.gov.
authors.forename: Tyler B
authors.initials: TB
authors.lastname: Coplen
authors.affiliation: U.S Geological Survey, 431 National Center, Reston, VA 20192, USA.
authors.forename: Haiping
authors.initials: H
authors.lastname: Qi
mesh_terms: D044707:Forensic Sciences / Q000592:standards*; D006197:Hair / Q000737:chemistry*; D006801:Humans; D006859:Hydrogen / Q000737:chemistry*; D007554:Isotopes / Q000032:analysis / Q000737:chemistry / Q000592:standards; D012015:Reference Standards; D015203:Reproducibility of Results
chemical_list: D007554:Isotopes; D006859:Hydrogen
keywords: Hydrogen isotopes; Keratin