Electrospray ionization MS of high MW TAG oligomers

Reported are the on-line LC/electrospray ionization MS of large, high M.W. oligomers formed from heated triolein, a TAG used as a model for dietary oils. Triolein, the major component of olive oil, canola oil, and other dietary oils, was heated at frying temperature, and the TAG oxidation products were separated using RP-HPLC coupled to an ion trap mass spectrometer via an electrospray ionization interface. Ammonium formate was added as a sheath liquid to promote ammonium adduct formation. Masses corresponding to ammonium adducts of intact carbon-linked dinners (m/z 1783-1787), trimers (m/z 2666-2672), and tetramers (m/z 3547-3557) of triolein, with and without additional sites of unsaturation, were observed. Also, dinners, trimers, and tetramers containing one, two, or three additional oxygens, also with and without additional sites of unsaturation, are reported. Based on the formation of some types of triolein dinners, we believe that tristearin might also form dinners, even though it has no readily oxidizable sites of unsaturation. Oxidized tristearin monomers, tristearin dinners, chain-addition products, and chain-shortened products are observed.