有机溶剂稀释与气相色谱-燃烧-同位素质谱（GC-C-IRMS）联用测定食醋中乙酸的δ13C

食醋中乙酸的碳-13比值（δ¹³C）与食醋原料有密切关联，通过测定乙酸中δ¹³C可对食醋原料进行溯源。本工作建立了有机溶剂稀释法与气相色谱-燃烧-稳定同位素比值质谱（GC-C-IRMS）联用法测定食醋中乙酸的δ¹³C。在乙酸浓度为2%~99.9%的模拟样品测试中获得了稳定的检测结果；同一样品中乙酸的δ¹³C重复测定16次的标准偏差小于0.15‰；参与欧盟同位素实验室间能力测试时，该方法的测定结果与其中5个国际实验室测定平均值差异为0.17‰。该方法的精密度和稳定性好、准确性高、操作简便快速，适合在食醋真实性技术中应用和推广。

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.