液相色谱-同位素比值质谱法测定食醋中乳酸和乙酸的δ^(13)C值

Determination of δ^(13)C value of lactic acid and acetic acid in vinegar by LC-IRMS

建立液相色谱-同位素比值质谱联用技术(LC-IRMS)测定食醋中乳酸和乙酸碳同位素比值δ^(13)C的方法。样品经沉淀剂沉淀蛋白质和C18固相萃取(SPE)净化后,采用Zorbax SB-Aq(250 mm×4. 6 mm,5μm)耐水反相色谱柱分离,用0. 3 mL/min 0. 05%H3PO4水溶液洗脱,柱温30℃。样本范围内,山西老陈醋和镇江香醋的乳酸和乙酸δ^(13)C值范围分别为-23. 40‰～-22. 39‰,-19. 52‰～-15. 16‰和-28. 06‰～-20. 81‰,-28. 28‰～-26. 90‰,白醋和米醋的乙酸δ^(13)C值范围分别为-29. 53‰～-18. 98‰和-29. 49‰～-13. 87‰。对4类食醋的乳酸和乙酸δ^(13)C值进行单因素方差分析,结果表明可以有效区分山西老陈醋、镇江香醋、白醋和米醋。该方法可应用于食醋产品标识的真实性鉴别研究中。

A method was developed for the determination of δ13C value of lactic acid and acetic acid in vinegar by liquid chromatography isotope ratio mass spectrometry (LC-IRMS).The samples were purified by precipitated protein,and then were operated by C18 solid phase extraction column (SPE).The compounds were separated by a Zorbax SB-Aq column(250×4.6 mm,5μm)with water resistant reversed phase,which were eluted with 0.05%H3PO4 water solution at 0.3 mL/min.The column temperature was 30℃.The range of δ13C value of lactic acid and acetic acid in Shanxi mature vinegar and Zhenjiang fragrant vinegar,was -23.40‰^-22.39‰,-19.52‰^-15.16‰ and -28.06%^-20.81‰,-28.28‰^-26.90‰,respectively.The range of δ13C value of acetic acid in white vinegar and rice vinegar was -9.53‰^-18.98%0 and -29.49‰^-13.87‰, respectively.The analysis of variance result showed that the determination of δ13C value of lactic acid and acetic acid in vinegar by LC-IRMS can effectively distinguish Shanxi mature vinegar,Zhenjiang fragrant vinegar,white vinegar and rice vinegar.The method is accurate and stable,and can be applied to the authenticity identification of vinegar products.