Determination of H-2/H-1 and C-13/C-12 isotope ratios of (E)-methyl cinnamate from different sources using isotope ratio mass spectrometry

摘要

For the authenticity assessment of (E)-methyl cinnamate from different origins, combustion/pyrolysis-isotope ratio mass spectrometry (C/P-IRMS) was used by an elemental analyzer (EA) and on-line capillary gas chromatography coupling (HRGC-C/P-IRMS). For that reason, (E)-methyl cinnamate self-prepared from synthetic, natural, and semisynthetic educts was analyzed in comparison to the commercial synthetic and natural ester. In addition, (E)-methyl cinnamate from basil extract and a number of commercial natural aromas was investigated. The data of self-synthesized synthetic (E)methyl cinnamate, i.e., delta(13)C(V-PDB) = -33.8parts per thousand and delta(2)H(V-SMOW) = +349parts per thousand, corresponded with that found for the commercial synthetic samples (-29.5 to -31.4parts per thousand and +328 to +360parts per thousand for delta(13)C(V-PDB) and delta(2)H(V-SMOW), respectively). The ester produced from natural educts by acid as well as Candida antarctica catalysis revealed delta(13)C(V-PDB) = -25.6 and -30.1parts per thousand as well as delta(2)H(V-SMOW) = -162 and -169parts per thousand, respectively. Acid-catalyzed semisynthetic products differed in their delta(13)C(V-PDB) and delta(2)H(V-SMOW) values depending on the origin of their educts. For the ester from synthetic methanol and natural cinnamic acid, -27.3 and -126parts per thousand were determined for delta(13)C(V-PDB) and delta(2)H(V-SMOW), respectively, whereas for the ester produced from natural methanol and synthetic acid delta(13)C(V-PDB) = -30.6parts per thousand and delta(2)H(V-SMOW) = +287parts per thousand were found. Basil extract showed -28.9 and -133parts per thousand for delta(13)C(V-PDB) and delta(2)H(V-SMOW), respectively. Commercial aromas declared to be natural revealed delta(13)C(V-PDB) and delta(2)H(V-SMOW) data ranging from -25.7 to -28.5parts per thousand as well as -85 to -191parts per thousand, respectively, indicating, in part, incorrect declaration.