GasBench/isotope ratio mass spectrometry:: a carbon isotope approach to detect exogenous CO2 in sparkling drinks

A new procedure for the determination of carbon dioxide (CO2) C-13/C-12 isotope ratios, using direct injection into a GasBench/isotope ratio mass spectrometry (GasBench/IRMS) system, has been developed to improve isotopic methods devoted to the study of the authenticity of sparkling drinks. Thirty-nine commercial sparkling drink samples from various origins were analyzed. Values of delta C-13(cava) ranged from -20.30 parts per thousand to -23.63 parts per thousand, when C3 sugar addition was performed for a second alcoholic fermentation. Values of delta C-13(water) ranged from -5.59 parts per thousand to -6.87 parts per thousand in the case of naturally carbonated water or water fortified with gas from the spring, and delta C-13(water) ranged from -29.36 parts per thousand to -42.09 parts per thousand when industrial CO2 was added. It has been demonstrated that the addition of C4 sugar to semi-sparkling wine (aguja) and industrial CO2 addition to sparkling wine (cava) or water can be detected. The new procedure has advantages over existing methods in terms of analysis time and sample treatment. In addition, it is the first isotopic method developed that allows C-13/C-12 determination directly from a liquid sample without previous CO2 extraction. No significant isotopic fractionation was observed nor any influence by secondary compounds present in the liquid phase. Copyright (c) 2007 John Wiley & Sons, Ltd.