title: Enantiomeric separation in comprehensive two-dimensional gas chromatography with accurate mass analysis.
abstract: Chiral comprehensive two-dimensional gas chromatography (eGC×GC) coupled to quadrupole-accurate mass time-of-flight mass spectrometry (QTOFMS) was evaluated for its capability to report the chiral composition of several monoterpenes, namely, α-pinene, β-pinene, and limonene in cardamom oil. Enantiomers in a standard mixture were fully resolved by direct enantiomeric-GC analysis with a 2,3-di-O-methyl-6-t-butylsilyl derivatized β-cyclodextrin phase; however, the (+)-(R)-limonene enantiomer in cardamom oil was overlapped with other background components including cymene and cineole. Verification of (+)-(R)-limonene components based on characteristic ions at m/z 136, 121, and 107 acquired by chiral single-dimension GC-QTOFMS in the alternate MS/MSMS mode of operation was unsuccessful due to similar parent/daughter ions generated by interfering or co-eluting cymene and cineole. Column phases SUPELCOWAX, SLB-IL111, HP-88, and SLB-IL59, were incorporated as the second dimension column ((2)D) in chiral GC×GC analysis; the SLB-IL59 offered the best resolution for the tested monoterpene enantiomers from the matrix background. Enantiomeric ratios for α-pinene, β-pinene, and limonene were determined to be 1.325, 2.703, and 1.040, respectively, in the cardamom oil sample based on relative peak area data.
authors.affiliation: Australian Centre for Research on Separation Science, School of Chemistry, Monash University, Clayton, VIC, Australia.
authors.forename: Sung-Tong
authors.initials: ST
authors.lastname: Chin
authors.forename: Yada
authors.initials: Y
authors.lastname: Nolvachai
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Marriott
keywords: accurate-mass mass spectrometry; collision induced dissociation; comprehensive two-dimensional gas chromatography; enantioselective analysis; tandem mass spectrometry