Detection of Vinegar Total Carbon Isotope Ratio by Elemental Analysis-Isotope Ratio Mass Spectrometry
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Abstract:
A method was established for determining the carbon isotope ratio of vinegars by elemental analysis-isotope ratio mass spectrometry (EA-IRMS), and cluster analysis was conducted on the vinegar samples. The sample dilution factor and injection volume were optimized; 2 g of balsamic vinegar was diluted in 4 mL of ultrapure water, 2 g of vinegar made from sticky rice was diluted with 2 mL of ultrapure water, and apple vinegar and blended white vinegar were not diluted. The sample injection volume was 1 μL and the sample analysis time was 670 s. The results indicated that the δ13C values of the balsamic vinegar, sticky rice vinegar, apple vinegar, and blended white vinegar were in the ranges of –(26.94-23.46%), -(25.06-22.40%), -(27.99-22.76%) and -(19.06-13.74%), respectively. The vinegars produced from different regions, with different raw materials, and different modes were preliminarily classified by cluster analysis, and this method could distinguish between pure balsamic vinegar samples and balsamic vinegar samples blended with ≥4% sticky rice fermented vinegar, ≥6% apple vinegar, and ≥2% blended white vinegar. The precision (standard deviation, SD) of vinegars and caffeine (quality control sample) were between 0.02% and 0.25% (n = 6), and were all less than 0.3%. This method can meet the requirements for determination. The results show that the established EA-IRMS method combined with cluster analysis can be applied for classification of vinegars and detection of adulterations in vinegar.
