GAS-CHROMATOGRAPHIC ANALYSIS OF GLYOXAL AND METHYLGLYOXAL FORMED FROM LIPIDS AND RELATED-COMPOUNDS UPON ULTRAVIOLET-IRRADIATION

Glyoxal, methylglyoxal (MG), malonaldehyde (MA), acrolein, formaldehyde, acetaldehyde, and propanal formed from squalene, cod liver oil, ethyl esters of fatty acids, and volatile aldehydes upon UV irradiation were derivatized to nitrogen- or sulfur-containing compounds. Derivatives were analyzed by a gas chromatograph equipped with a nitrogen-phosphorus detector or a flame photometric detector. Maximum amounts of glyoxal (9.6 nmol/mg) and MG (14 nmol/mg) formed from squalene after 10 h of UV irradiation. Cod liver oil also produced glyoxal (27 nmol/mg) and MG (5.7 nmol/mg). Glyoxal was formed at concentrations of 10 nmol/mg from ethyl linoleate, 32 nmol/mg from ethyl linolenate, and 50 nmol/mg from ethyl arachidonate. MG was also formed from the ethyl esters of fatty acids. MA and acrolein were formed from squalene, cod liver oil, and ethyl esters of fatty acids under the same conditions. Glyoxal and MG were produced from acetaldehyde, acrolein, and propanal in the range 2-9 nmol/mg. Prior to this study, glyoxal and MG had never been reported as photodegradation products of lipids or fatty acids.