title: A novel high-temperature combustion interface for compound-specific stable isotope analysis of carbon and nitrogen via high-performance liquid chromatography/isotope ratio mass spectrometry.
abstract: BACKGROUND
  In aqueous samples compound-specific stable isotope analysis (CSIA) plays an important role. No direct method (without sample preparation) for stable nitrogen isotope analysis (δ(15) N SIA) of non-volatile compounds is known yet. The development of a novel HPLC/IRMS interface based on high-temperature combustion (HTC) for both δ(13) C and δ(15) N CSIA and its proof of principle are described in this study.
  
  
  METHODS
  To hyphenate high-performance liquid chromatography (HPLC) with isotope ratio mass spectrometry (IRMS) a modified high-temperature combustion total organic carbon analyzer (HTC TOC) was used. A system to handle a continuously large amount of water (three-step drying system), favorable carrier and reaction gas mix and flow, an efficient high-temperature-based oxidation and subsequent reduction system and a collimated beam transfer system were the main requirements to achieve the necessary performance.
  
  
  RESULTS
  The proof of principle with caffeine solutions of the system succeeded. In this initial testing, both δ(13) C and δ(15) N values of tested compounds were determined with precision and trueness of ≤0.5 ‰. Further tests resulted in lower working limit values of 3.5 μgC for δ(13) C SIA and 20 μgN for δ(15) N SIA, considering an accuracy of ±0.5 ‰ as acceptable.
  
  
  CONCLUSIONS
  The development of a novel HPLC/IRMS interface resulted in the first system reported to be suitable for both δ(13) C and δ(15) N direct CSIA of non-volatile compounds. This highly efficient system will probably open up new possibilities in SIA-based research fields. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Research and Innovation, Elementar Analysensysteme GmbH, Donaustr. 7, 63452, Hanau, Germany.|Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstr. 5, 45141, Essen, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Federherr
authors.affiliation: Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstr. 5, 45141, Essen, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Willach
authors.affiliation: Application Development Support, Agilent Technologies Sales & Services GmbH und Co.KG, Lyoner Straße 20, 60528, Frankfurt am Main, Germany.
authors.forename: N
authors.initials: N
authors.lastname: Roos
authors.affiliation: Research and Innovation, Elementar Analysensysteme GmbH, Donaustr. 7, 63452, Hanau, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Lange
authors.affiliation: Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstr. 5, 45141, Essen, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Molt
authors.affiliation: Instrumental Analytical Chemistry, University of Duisburg-Essen, Universitätsstr. 5, 45141, Essen, Germany.
authors.forename: T C
authors.initials: TC
authors.lastname: Schmidt
mesh_terms: D002247:Carbon Isotopes / Q000032:analysis* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004867:Equipment Design; D006358:Hot Temperature; D007553:Isotope Labeling; D013058:Mass Spectrometry / Q000379:methods*; D009587:Nitrogen Isotopes / Q000032:analysis* / Q000737:chemistry; D015203:Reproducibility of Results
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes