Determination of Carbon Isotope Ratio of Acetic Acid in Vinegar by GC-C-IRMS Coupled with Organic Solvent Dilution

Stable carbon isotope composition (δ¹³C) of acetic acid is a valuable character as tracer for raw fermentation material of vinegar, however， the analytical technique still remains be estimated. Now, a rapid method for the determination of δ¹³C of acetic acid in vinegar by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) coupled with a capillary column was developed. Results demonstrate that the method above is stable with a standard deviation (1σ) lower than 0.15‰ (n=16) with which other organic compounds in vinegar can be ignored, and the variation of δ¹³C determination is very small while acetic acid range from 2% to 99.9%. We take participant in a FIT Proficiency Testing Scheme for an inter-laboratory comparison study of carbon isotopic methods of acetic acid, and the difference is 0.17‰ between the measurement and the mean value of 5 laboratories. This method has an advantage of easy and rapid operating, and which is applicable for δ¹³C analysis of acetic acid for vinegar authenticity control.