title: Calibration and data processing in gas chromatography combustion isotope ratio mass spectrometry.
abstract: Compound-specific isotope analysis (CSIA) by gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) is a powerful technique for the sourcing of substances, such as determination of the geographic or chemical origin of drugs and food adulteration, and it is especially invaluable as a confirmatory tool for detection of the use of synthetic steroids in competitive sport. We review here principles and practices for data processing and calibration of GCC-IRMS data with consideration to anti-doping analyses, with a focus on carbon isotopic analysis ((13)C/(12)C). After a brief review of peak definition, the isotopologue signal reduction methods of summation, curve-fitting, and linear regression are described and reviewed. Principles for isotopic calibration are considered in the context of the Δ(13)C = δ(13)C(M) - δ(13)C(E) difference measurements required for establishing adverse analytical findings for metabolites (M) relative to endogenous (E) reference compounds. Considerations for the anti-doping analyst are reviewed.
authors.affiliation: Cornell University, Division of Nutritional Sciences, Savage Hall, Ithaca, NY 14853, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Herbert J
authors.initials: HJ
authors.lastname: Tobias
authors.forename: Gavin L
authors.initials: GL
authors.lastname: Sacks
authors.forename: J Thomas
authors.initials: JT
authors.lastname: Brenna
mesh_terms: D045930:Anabolic Agents / Q000652:urine*; D015415:Biomarkers / Q000652:urine; D002138:Calibration; D002247:Carbon Isotopes / Q000652:urine*; D004300:Doping in Sports; D004867:Equipment Design; D008401:Gas Chromatography-Mass Spectrometry / Q000295:instrumentation / Q000592:standards*; D006801:Humans; D016014:Linear Models; D058573:Performance-Enhancing Substances / Q000652:urine*; D011237:Predictive Value of Tests; D011786:Quality Control; D012015:Reference Standards; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D013256:Steroids / Q000652:urine*; D015813:Substance Abuse Detection / Q000295:instrumentation / Q000379:methods / Q000592:standards*
chemical_list: D045930:Anabolic Agents; D015415:Biomarkers; D002247:Carbon Isotopes; D058573:Performance-Enhancing Substances; D013256:Steroids