Caffeine in Your Drink: Natural or Synthetic?

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• 作者：Lijun Zhang ; Dorothea M. Kujawinski ; Eugen Federherr ; Torsten C. Schmidt ; Maik A. Jochmann
• 刊名：Analytical Chemistry
• 出版年：2012
• 出版时间：March 20, 2012
• 年：2012
• 卷：84
• 期：6
• 页码：2805-2810
• 全文大小：303K
• 年卷期：v.84,no.6(March 20, 2012)
• ISSN：1520-6882

文摘

Owing to possible adulteration and health concerns, it is important to discriminate between natural and synthetic food ingredients. A new method for compound-specific isotope analysis (CSIA) by coupling high-temperature reversed-phase liquid chromatography to isotope ratio mass spectrometry (HT-RPLC/IRMS) was developed for discrimination of natural and synthetic caffeine contained in all types of drinks. The analytical parameters such as stationary phase, column inner diameter, and column temperature were optimized for the separation of caffeine directly from drinks (without extraction). On the basis of the carbon isotope analysis of 42 natural caffeine samples including coffee beans, tea leaves, guaran谩 powder, and mat茅 leaves, and 20 synthetic caffeine samples from different sources by high-temperature reversed-phase liquid chromatography coupled to isotope ratio mass spectrometry, it is concluded that there are two distinguishable groups of caffeine 未¹³C-values: one between 鈭?5 and 鈭?2鈥?for natural caffeine, and the other between 鈭?3 and 鈭?8鈥?for synthetic caffeine. Isotope analysis by HT-RPLC/IRMS has been applied to identify the caffeine source in 38 drinks. Four mislabeled products were detected due to added but nonlabeled synthetic caffeine with 未¹³C-values lower than 鈭?3鈥? This work is the first application of HT-RPLC/IRMS to real-world food samples, which showed several advantages: simple sample preparation (only dilution), high throughput, long-term column stability, and high precision of 未¹³C-value. Thus, HT-RPLC/IRMS can be a very promising tool in stable isotope analysis of nonvolatile compounds.