- We found a large number of fatty acid esters in the ant heads. These esters span the molecular weight range of 312.3 up to 438.3 and all of them shared the low mass fragment m/z=98.1, characteristics for heptyl esters. The acyl moiety constitutes a range of linear and branched fatty acids, corresponding to the free fatty acids found also in the head (see below). These esters were as abundant as the ant wax hydrocarbons and found in all three heads that were studies while they were absent in all the other body and gland parts. Possibly this is a new and interesting finding and its significance should be further explored.
- We found that the ant parts included acids, both with linear chain and branched acids. The heads included larger relative amount of free acids with greater abundance and variety of branched free fatty acids isomers.
- We found several steroid based free acids in the form of few isomers with m/z=302.3 and one with m/z=300.3. These steroid acids were found in head #3 but not in head samples number 2 and 1. These acids were also found in the Gaster and Thorax samples. The finding of these steroid based free acids is new as they can not be analyzed by GC-MS with standard EI without derivatization.
- All the ant parts and glands exhibited wax hydrocarbons in both linear chain and branched isomers forms.
- The 5975-SMB GC-MS with Cold EI opens the door for a unique and highly effective isomer distribution analysis characterization of the ant wax hydrocarbons, acids and esters. The unique finding of esters was also accompanied by the finding that each ester had a few isomers. Thus, we feel that isomer distribution analysis can serve as a novel tool for ant chemical ecology studies.
|Figure 4. Total ion mass chromatogram of Cataglyphis ant head #2 (upper trace) and the Cold EI mass spectrum of a typical ester with molecular ion m/z=368.4 (bottom trace) that eluted at 9.42 min. Note the informative Cold EI mass spectrum.|