title: Potential of ion chromatography coupled to isotope ratio mass spectrometry via a liquid interface for beverages authentication.
abstract: New tools for the determination of characteristic parameters for food authentication are requested to prevent food adulteration from which health concerns, unfair competition could follow. A new coupling in the area of compound-specific carbon 13 isotope ratio (δ(13)C) analysis was developed to simultaneously quantify δ(13)C values of sugars and organic acids. The coupling of ion chromatography (IC) together with isotope ratio mass spectrometry (IRMS) can be achieved using a liquid interface allowing a chemical oxidation (co) of organic matter. Synthetic solutions containing 1 polyol (glycerol), 3 carbohydrates (sucrose, glucose and fructose) and 12 organic acids (gluconic, lactic, malic, tartaric, oxalic, fumaric, citric and isocitric) were used to optimize chromatographic conditions (concentration gradient and 3 types of column) and the studied isotopic range (-32.28 to -10.65‰) corresponds to the values found in food products. Optimum chromatographic conditions are found using an IonPac AS15, an elution flow rate of 0.3mLmin(-1) and a linear concentration gradient from 2 to 76mM (rate 21mMmin(-1)). Comparison between δ(13)C value individually obtained for each compound with the coupling IRMS and elemental analyzer, EA-IRMS, and the ones measured on the mixture of compounds by IC-co-IRMS does not reveal any isotope fractionation. Thus, under these experimental conditions, IC-co-IRMS results are accurate and reproducible. This new coupling was tested on two food matrices, an orange juice and a sweet wine. Some optimization is necessary as the concentration range between sugars and organic acids is too large: an increase in the filament intensity of the IRMS is necessary to simultaneously detect the two compound families. These first attempts confirm the good results obtained on synthetic solutions and the strong potential of the coupling IC-co-IRMS in food authentication area.
authors.affiliation: Service Commun des Laboratoires, 3 Avenue du Dr A. Schweitzer, 33608 Pessac, France. Electronic address: francois.guyon@scl.finances.gouv.fr.
authors.forename: Francois
authors.initials: F
authors.lastname: Guyon
authors.forename: Laetitia
authors.initials: L
authors.lastname: Gaillard
authors.forename: Audrey
authors.initials: A
authors.lastname: Brault
authors.forename: Nicolas
authors.initials: N
authors.lastname: Gaultier
authors.forename: Marie-Hélène
authors.initials: MH
authors.lastname: Salagoïty
authors.forename: Bernard
authors.initials: B
authors.lastname: Médina
mesh_terms: D001628:Beverages / Q000032:analysis*; D002247:Carbon Isotopes / Q000032:analysis; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D002852:Chromatography, Ion Exchange / Q000295:instrumentation / Q000379:methods*; D013058:Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D015203:Reproducibility of Results
chemical_list: D002247:Carbon Isotopes
keywords: Carbohydrates; Ion chromatography; Isotope ratio mass spectrometry; Orange juice; Organic acids; Sweet wine