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J Agric Food Chem. 2011 Mar 23;59(6):2229-34. doi: 10.1021/jf104527e. Epub 2011 Feb 28.
Organic acid analysis plays a fundamental role in the testing of authenticity of fruit juices. Analytical methods used routinely for organic acids suffer from poor reproducibility, often give false positives/negatives for tartaric acid, and do not offer the possibility of analyte confirmation. There are conflicting reports in the literature on the presence/absence of tartaric acid in pomegranate juice, a potential indicator of adulteration with grape juice. In this work, a method based on stable isotope dilution liquid chromatography-tandem mass spectrometry is described for citric, malic, quinic, and tartaric acid in fruit juices. Validation data including precision and recovery in six types of juice are presented. Tartaric and quinic acids were confirmed in pomegranate juice at concentrations of 1-5 and ∼1 mg/L, respectively. These concentrations are much lower than those resulting from adulteration with grape juice and apple juice, respectively, at the 5% level. A separate method for isocitric acid in orange juice based on the single standard addition method is also described.
有机酸分析在果汁真实性测试中起着至关重要的作用。用于有机酸分析的常规分析方法重现性差，常对酒石酸产生假阳性/假阴性结果，并且不具备分析物确认的可能性。关于石榴汁中是否存在酒石酸存在争议，酒石酸是果汁掺假的潜在指标。在这项工作中，描述了一种基于稳定同位素稀释液相色谱-串联质谱法的果汁中柠檬酸、苹果酸、奎尼酸和酒石酸的分析方法。提供了包括 6 种果汁的精密度和回收率在内的验证数据。在石榴汁中分别确认了浓度为 1-5 和约 1mg/L 的酒石酸和奎尼酸。这些浓度远低于分别用葡萄汁和苹果汁掺假在 5%水平下的浓度。还描述了一种基于单标准添加法的橙汁中异柠檬酸的单独方法。
