title: Comparison of gas chromatography/isotope ratio mass spectrometry and liquid chromatography/isotope ratio mass spectrometry for carbon stable-isotope analysis of carbohydrates.
abstract: BACKGROUND
  We compared gas chromatography/isotope ratio mass spectrometry (GC/IRMS) and liquid chromatography/isotope ratio mass spectrometry (LC/IRMS) for the measurement of δ(13)C values in carbohydrates. Contrary to GC/IRMS, no derivatisation is needed for LC/IRMS analysis of carbohydrates. Hence, although LC/IRMS is expected to be more accurate and precise, no direct comparison has been reported.
  
  
  METHODS
  GC/IRMS with the aldonitrile penta-acetate (ANPA) derivatisation method was compared with LC/IRMS without derivatisation. A large number of glucose standards and a variety of natural samples were analysed for five neutral carbohydrates at natural abundance as well as at (13)C-enriched levels. Gas chromatography/chemical ionisation mass spectrometry (GC/CIMS) was applied to check for incomplete derivatisation of the carbohydrate, which would impair the accuracy of the GC/IRMS method.
  
  
  RESULTS
  The LC/IRMS technique provided excellent precision (±0.08‰ and ±3.1‰ at natural abundance and enrichment levels, respectively) for the glucose standards and this technique proved to be superior to GC/IRMS (±0.62‰ and ±19.8‰ at natural abundance and enrichment levels, respectively). For GC/IRMS measurements the derivatisation correction and the conversion of carbohydrates into CO2 had a considerable effect on the measured δ(13)C values. However, we did not find any significant differences in the accuracy of the two techniques over the full range of natural δ(13)C abundances and (13)C-labelled glucose. The difference in the performance of GC/IRMS and LC/IRMS diminished when the δ(13)C values were measured in natural samples, because the chromatographic performance and background correction became critical factors, particularly for LC/IRMS. The derivatisation of carbohydrates for the GC/IRMS method was complete.
  
  
  CONCLUSIONS
  Although both LC/IRMS and GC/IRMS are reliable techniques for compound-specific stable carbon isotope analysis of carbohydrates (provided that derivatisation is complete and the calibration requirements are met), LC/IRMS is the technique of choice. The reasons for this are the improved precision, simpler sample preparation, and straightforward isotopic calibration.
authors.affiliation: Royal Netherlands Institute for Sea Research (NIOZ), Korringaweg 7, 4401 NT, Yerseke, The Netherlands.
authors.forename: Tanja C W
authors.initials: TC
authors.lastname: Moerdijk-Poortvliet
authors.affiliation: Department of Pediatrics, AMC - Emma Children's Hospital, University of Amsterdam, Amsterdam, The Netherlands.|Department of Pediatrics, VU, University Medical Centre, Amsterdam, The Netherlands.
authors.forename: Henk
authors.initials: H
authors.lastname: Schierbeek
authors.affiliation: Royal Netherlands Institute for Sea Research (NIOZ), Korringaweg 7, 4401 NT, Yerseke, The Netherlands.
authors.forename: Marco
authors.initials: M
authors.lastname: Houtekamer
authors.affiliation: Royal Netherlands Institute for Sea Research (NIOZ), Korringaweg 7, 4401 NT, Yerseke, The Netherlands.
authors.forename: Tom
authors.initials: T
authors.lastname: van Engeland
authors.affiliation: Inra, Biogéochimie des Ecosystèmes Forestiers, UR1138, Champenoux, F-54280, France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Derrien
authors.affiliation: Royal Netherlands Institute for Sea Research (NIOZ), Korringaweg 7, 4401 NT, Yerseke, The Netherlands.|Department of Aquatic Microbiology, IBED, University of Amsterdam, The Netherlands.
authors.forename: Lucas J
authors.initials: LJ
authors.lastname: Stal
authors.affiliation: Royal Netherlands Institute for Sea Research (NIOZ), Korringaweg 7, 4401 NT, Yerseke, The Netherlands.
authors.forename: Henricus T S
authors.initials: HT
authors.lastname: Boschker
mesh_terms: D002138:Calibration; D002241:Carbohydrates / Q000032:analysis; D002247:Carbon Isotopes / Q000032:analysis*; D002853:Chromatography, Liquid / Q000379:methods* / Q000592:standards; D031751:Festuca / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods* / Q000592:standards; D005947:Glucose / Q000032:analysis; D013058:Mass Spectrometry / Q000379:methods* / Q000592:standards; D044445:Ulva / Q000737:chemistry; D003313:Zea mays / Q000737:chemistry
chemical_list: D002241:Carbohydrates; D002247:Carbon Isotopes; D005947:Glucose