On-Line Gas Chromatography Combustion/Pyrolysis Isotope Ratio Mass Spectrometry (HRGC-C/P-IRMS) of Pineapple (Ananas comosus L. Merr.) Volatiles

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Abstract
By use of extracts prepared by liquid−liquid separation of the volatiles from self-prepared juices of pineapple fruits (Ananas comosus) (n = 14) as well as commercial pineapple recovery aromas/water phases (n = 3), on-line capillary gas chromatography-isotope ratio mass spectrometry was employed in the combustion (C) and the pyrolysis (P) modes (HRGC-C/P-IRMS) to determine the δ13CVPDB and δ2HVSMOW values of selected pineapple flavor constituents. In addition to methyl 2-methylbutanoate 1, ethyl 2-methylbutanoate 2, methyl hexanoate 3, ethyl hexanoate 4, and 2,5-dimethyl-4-methoxy-3[2H]-furanone 5, each originating from the fruit, the δ13CVPDB and δ2HVSMOW data of commercial synthetic 1−5 and “natural” (biotechnologically derived) 1−4 were determined. With δ13CVPDB data of pineapple volatiles 1−4 varying from −12.8 to −24.4‰, the range expected for CAM metabolism was observed. Compound 5 showed higher depletion from −20.9 to −28.6‰. A similar situation was given for the δ2HVSMOW values of 3−5 from pineapple ranging from −118 to −191‰, whereas 1 and 2 showed higher depleted values from −184 to −263‰. In nearly all cases, analytical differentiation of 1−5 from pineapple and natural as well as synthetic origin was possible. In general, natural and synthetic 1−5 exhibited δ13CVPDB data ranging from −11.8 to −32.2‰ and −22.7 to −35.9‰, respectively. Their δ2HVSMOW data were in the range from −242 to −323‰ and −49 to −163‰, respectively. Keywords: Pineapple (Ananas comosus); isotope ratio mass spectrometry; IRMS; HRGC−C/P−IRMS; 13C/12C ratio, 2H/1H ratio; methyl 2-methylbutanoate, ethyl 2-methylbutanoate, methyl hexanoate, ethyl hexanoate, 2,5-dimethyl-4-methoxy-3[2H]-furanone