A new method to analysis synthetic acetic acid to vinegar: Hydrogen isotope ratio at the methyl site of acetic acid in vinegar by GC-IRMS.

Acetic acid is the key organic substance used to verify the authenticity of vinegar. A new method for precisely determining acetic acid δD _CH3 in vinegar via gas chromatography -pyrolytic-stable isotope ratio mass spectrometry (GC-P-IRMS) was established. The δD _CH3 values were obtained via calibration with a series of standards. The optimised method demonstrated a repeatability standard deviation within 3 ‰. The standard deviation of accuracy of the new method compared with that of the SNIF-NMR method was within 2.6 ‰. The synthetic acetic acid δD _CH3 values was -136.7 ‰ ± 29.6 ‰, and the δD _CH3 value of acetic acid in vinegar was -414.9 ‰ ± 40.5 ‰, with significant isotopic distribution characteristics. This methodology serves as a supplementary method for measuring the δD _CH3 value of acetic acid in vinegar. It has advantages over other methods in terms of time, sensitivity and operability. And provides a new idea for solving the problem of analyzing substances in the presence of exchangeable groups.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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