| Title: | Gaseous byproducts from high-temperature thermal conversion elemental analysis of nitrogen- and sulfur-bearing compounds with considerations for delta2H and delta18O analyses |
| Author(s): | Hunsinger GB; Tipple CA; Stern LA; |
| Address: | "Counterterrorism and Forensic Science Research Unit, FBI Laboratory, Quantico, VA 22135, USA" |
| Journal Title: | Rapid Commun Mass Spectrom |
| ISSN/ISBN: | 1097-0231 (Electronic) 0951-4198 (Linking) |
| Abstract: | "RATIONALE: High-temperature, conversion-reduction (HTC) systems convert hydrogen and oxygen in materials into H2 and CO for delta(2)H and delta(18)O measurements by isotope ratio mass spectrometry. HTC of nitrogen- and sulfur-bearing materials produces unintended byproduct gases that could affect isotope analyses by: (1) allowing isotope exchange reactions downstream of the HTC reactor, (2) creating isobaric or co-elution interferences, and (3) causing deterioration of the chromatography. This study characterizes these HTC byproducts. METHODS: A HTC system (ThermoFinnigan TC/EA) was directly connected to a gas chromatograph/quadrupole mass spectrometer in scan mode (m/z 8 to 88) to identify the volatile products generated by HTC at conversion temperatures of 1350 degrees C and 1450 degrees C for a range of nitrogen- and sulfur-bearing solids [keratin powder, horse hair, caffeine, ammonium nitrate, potassium nitrate, ammonium sulfate, urea, and three nitrated organic explosives (PETN, RDX, and TNT)]. RESULTS: The prominent HTC byproduct gases include carbon dioxide, hydrogen cyanide, methane, acetylene, and water for all nitrogen-bearing compounds, as well as carbon disulfide, carbonyl sulfide, and hydrogen sulfide for sulfur-bearing compounds. The 1450 degrees C reactor temperature reduced the abundance of most byproduct gases, but increased the significant byproduct, hydrogen cyanide. Inclusion of a post-reactor chemical trap containing Ascarite II and Sicapent, in series, eliminated the majority of byproducts. CONCLUSIONS: This study identified numerous gaseous HTC byproducts. The potential adverse effects of these gases on isotope ratio analyses are unknown but may be mitigated by higher HTC reactor temperatures and purifying the products with a purge-and-trap system or with chemical traps" |
| Keywords: | "Animals Deuterium/*analysis Explosive Agents/chemistry Gas Chromatography-Mass Spectrometry/*methods Gases/analysis/chemistry Hair/chemistry Horses Hot Temperature Hydrogen Cyanide/chemistry Keratins/chemistry Models, Chemical Nitrates/chemistry Nitrogen;" |
| Notes: | "MedlineHunsinger, Glendon B Tipple, Christopher A Stern, Libby A eng Research Support, U.S. Gov't, Non-P.H.S. England 2013/06/12 Rapid Commun Mass Spectrom. 2013 Jul 30; 27(14):1649-59. doi: 10.1002/rcm.6608" |
