The CM–CRDS Method for Measuring the Carbon Isotope Ratio in Vanillin With an Expanded Uncertainty of Less Than 0.1 %

Isotopic analysis is an efficient method for quality control and detection of counterfeit food products. The method of elemental analysis isotope ratio mass spectrometry (hereinafter referred to as EA-IRMS) is traditionally used in the field of isotopic analysis of food products and is regulated in the relevant regulatory documents. The method of combustion module-cavity ring-down spectroscopy (hereinafter referred to as CM–CRDS) is a rapidly developing method for measuring the carbon isotope ratio with a number of advantages; currently, this method is of most interest for the isotope analysis of food products. However, studies of the metrological characteristics of the CM–CRDS method as part of the analysis of the isotopic composition of vanillin have not been carried out. The purpose of the research was to develop a procedure for measuring the carbon isotope ratio in vanillin by the CM–CRDS method with an expanded uncertainty (at k = 2) of less than 0.1 ‰.

The development of the measurement procedure was carried out in preparation for the international key comparison CCQM-K167 «Carbon isotope delta measurements of vanillin» (2019–2022) organized by the international Working Group on Isotope Ratios of the Consultative Committee for Amount of Substance of the International Bureau of Weights and Measures. The experimental part of the research was carried out on a reference installation, which is part of the State primary standard of units of molar part, mass part and mass concentration of components in gas and gas condensate environs GET 154-2019.

The expanded uncertainty (at k = 2) of this procedure for measuring the carbon isotope ratio in vanillin by the CM–CRDS method is less than 0.1 ‰. The following tasks were solved to achieve the set goal: the factors that form the measurement uncertainty budget were identified, some of which were eliminated or minimized by developing a procedure for preparing equipment and samples, a procedure for performing and controlling the measurement accuracy, and a procedure for processing measurement results.

The results of international comparisons CCQM-K167 confirmed the possibility of measuring the carbon isotope ratio in vanillin by the CM–CRDS method using the developed procedure with an expanded uncertainty (at k = 2) of 0.09 ‰, which corresponds to the best measurements performed by the EA-IRMS method.

The achieved result is of practical importance, because it confirms the possibility of applying the CM–CRDS method for quality control and detection of counterfeit vanillin.

Further research will be aimed at developing procedures for measuring the carbon isotope ratio using the CM–CRDS method in other substances and materials analyzed in the food industry, including for quality control and safety confirmation of juice products according to TR CU023/2011 and alcoholic products according to TR EAEU047/2018.

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