| Abstract: | In order to facilitate the gas chromatographic determination of butyric as well as other short chain fatty acids, triglycerides containing these fatty acids were transbutylated and transpentylated to give FABES (fatty acid butyl esters) and FAPES (fatty acid pentyl esters), respectively. This method allows the molecular weight of the compounds to be increased while their polarity is decreased. Short chain esters elute sufficiently separated from the solvent; due to the decreased polarity, elution of long chain fatty acids is only slightly retarded compared to the corresponding methyl esters. Quantitative evaluation over a large series of injections proved the linearity of correction factors in both cases, FABES and FAPES, with a slight deviation for 16:0 and 18:0, respectively. Structural characterization was performed by GC/MS. It was shown that there are characterstic fragmentations for FABES as well as for FAPES. The El-mass spectra give structural information about the alcohol and acid moieties, the ester molecule and the Cl-spectra indicate the molecular weight. The absence of abundant highly characteristic peaks in the spectra of these esters makes the detection of FABES or FAPES in complex mixtures more difficult than the detection of FAMES with their very characteristic ions at m/z 74 and 87. |
