title: A new concept for isotope ratio monitoring liquid chromatography/mass spectrometry.
abstract: A new interface for the on-line coupling of a liquid chromatograph to a stable isotope ratio mass spectrometer has been developed and tested. The interface is usable for (13)C/(12)C determination of organic compounds, allowing measurement of small changes in (13)C abundance in individual analyte species. All of the carbon in each analyte is quantitatively converted into CO(2) while the analyte is still dissolved in the aqueous liquid phase. This is accomplished by an oxidizing agent such as ammonium peroxodisulfate. The CO(2) is separated from the liquid phase and transferred to the mass spectrometer. It is shown that the whole integrated process does not introduce isotope fractionation. The measured carbon isotope ratios are accurate and reproducible. The sensitivity of the complete system allows isotope ratio determination down to 400 ng of compound on-column. By-passing the high-performance liquid chromatography (HPLC) separation allows bulk isotopic analysis with substantially lower sample amounts than those required by conventional elemental analyzers. The results of the first applications to amino acids, carbohydrates, and drugs, eluted from various types of HPLC columns, are presented. The wide range of chromatographic methods enables the analysis of compounds never before amenable to isotope ratio mass spectrometry techniques and may lead to the development of many new assays.
authors.affiliation: Thermo Electron Corporation, Finnigan Advanced Mass Spectrometry, Barkhausenstrasse 2, D-28197 Bremen, Germany. michael.krummen@thermo.com
authors.forename: Michael
authors.initials: M
authors.lastname: Krummen
authors.forename: Andreas W
authors.initials: AW
authors.lastname: Hilkert
authors.forename: Dieter
authors.initials: D
authors.lastname: Juchelka
authors.forename: Alexander
authors.initials: A
authors.lastname: Duhr
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Schlüter
authors.forename: Reinhold
authors.initials: R
authors.lastname: Pesch
mesh_terms: D002245:Carbon Dioxide / Q000032:analysis* / Q000737:chemistry; D002247:Carbon Isotopes / Q000032:analysis* / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D017022:Flow Injection Analysis / Q000379:methods*; D007553:Isotope Labeling / Q000379:methods; D013058:Mass Spectrometry / Q000379:methods*; D009862:Online Systems; D009930:Organic Chemicals / Q000032:analysis* / Q000737:chemistry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D002247:Carbon Isotopes; D009930:Organic Chemicals; D002245:Carbon Dioxide