Purification and Gas Chromatography–Combustion–Isotope Ratio Mass Spectrometry of Aroma Compounds from Green Tea Products and Comparison to Bulk Analysis

A method for carbon isotope ratio (δ13C) analysis was developed for compound-specific isotope analysis of tea volatiles, and the values were compared with the δ13C value from bulk isotope analyses. The δ13C value of 2-phenylethanol liberated via enzymatic hydrolysis of the 2-phenylethyl β-primeveroside standard was examined first. Isotope fractionations for 2-phenylethyl β-primeveroside from preparative high-performance liquid chromatography (HPLC) were also analyzed. The enzymatic treatment and the preparative HPLC process did not cause carbon isotope fractionations, substantiating the strategies available for δ13C analysis of volatile compounds. On the basis of the gas chromatography–combustion–isotope ratio mass spectrometry data from 2-phenylethanol, it was possible to derive the conditions for enzyme treatment and preparative HPLC of the glycoconjugates of 2-phenylethanol, (Z)-3-hexenol, and benzyl alcohol isolated from green tea leaves. Larger variations in δ13C were found for individual volatile co...