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Compositional analysis of intact alkyl esters in leaf epicuticular wax of swede by capillary gas chromatography and electron‐impact mass spectrometry
Author(s) -
Shepherd T.,
Robertson G. W.,
Griffiths D. W.
Publication year - 1995
Publication title -
phytochemical analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 72
eISSN - 1099-1565
pISSN - 0958-0344
DOI - 10.1002/pca.2800060202
Subject(s) - chemistry , chromatography , mass spectrometry , alcohol , gas chromatography , mass spectrum , gas chromatography–mass spectrometry , wax , electron ionization , trimethylsilyl , organic chemistry , ion , ionization
A method for the separation and identification of complex mixtures of more than 50 different intact esters in epicuticular wax of swede, Brassica napus var. rapifera cv. Doon Major, using combined gas chromatography‐mass spectrometry (GC‐MS) has been developed. The esters were separated at temperatures of up to 350°C by automatic pressure programming (for capillary GC) or by manually increasing helium carrier gas pressure (for GC‐MS) in order to maintain flow at high temperatures. Esters in the range C 41 ‐C 50 were detected, with regular repeating acid/alcohol combinations. Individual acid and alcohol moieties were identified from [RCO 2 H 2 ] + ions in the mass spectra of intact esters and, following trans‐esterification and silylation, from the mass spectral and chromatographic characteristics of the methyl esters of the acid components (C 14 ‐C 23 ) and trimethylsilyl derivatives of the alcohol components (C 23 ‐C 31 ). The major compounds were doubly branched C 44 and C 46 esters, composed of anteiso ‐C 17 / anteiso ‐C 27 (32.7%), anteiso ‐C 17 / anteiso ‐C 29 (11.9%) and anteiso ‐C 19 / anteiso ‐C 27 (13.1%) acid/alcohol combinations, respectively, singly branched C 43 and C 45 esters, composed of n‐C 16 / anteiso ‐C 27 (8.5%), anteiso ‐C 17 /n‐C 26 (3.9%), n‐C 18 / anteiso ‐C 27 (6.8%), anteiso ‐C 17 /n‐C 28 (2.3%) and anteiso ‐C 19 /n‐C 26 (1.6%), were minor components.