油酸和亚油酸异构体的气相色谱-质谱分析

Analysis of Oleic Acid and Linoleic Acid Isomers by Gas Chromatography-Mass Spectrometry

采用气相色谱-质谱法分析油酸和亚油酸异构体的出峰顺序和质谱特征,结果表明:脂肪酸在强极性毛细管柱BPX-70(120 m×0.25 mm×0.25μm)上的出峰顺序具有一定规律。油酸和亚油酸异构体中,出峰顺序依次为C_(18:1 6t)、C_(18:19t)、C_(18:1 11t)、C_(18:1 9c)、C_(18:1 11c)和C_(18:2 9t,12t)、C_(18:2 9c,12t)、C_(18:2 9t,12c)、C_(18:2 9c,12c)。根据断裂规律和质谱特征分析,油酸甲酯的特征离子为m/z 55(基峰离子)、222([M-74]^+)、264([M-32]^+)和296(M^+),而亚油酸甲酯的特征离子为m/z67(基峰离子)、220([M-74]^+)、263([M-31]^+)和294(M^+)。油酸和亚油酸的异构体分别具有相同的特征离子,且质谱图极为相近,说明不能通过特征离子和质谱图判断油酸和亚油酸异构体中的双键位置和顺反构象。

The peak sequences and mass spectrometry characteristics of oleic acid and linoleic acid isomers were studied by gas chromatography-mass spectrometry in this paper.The results indicated that the peak sequences of fatty acids were regular using the strong polar glass capillary column BPX-70（120 m × 0.25 mm × 0.25 μm）,and the peak sequences oleic acid and linoleic acid isomers were successively C_（18：1 6 t）,C_（18：1 9 t）,C_（18：1 11 t）,C_（18：1 9 c）,C_（18：1 11 c）,C_（18：2 9 t,12 t）,C_（18：2 9 c,12 t）,C_（18：2 9 t,12 c）,C_（18：2 9 c,12 c）.The characteristic ions of oleic acid methyl ester were m/z 55（base-peak ion）,222（[M-74]~＋）,264（[M-32]~＋） and 296（M~＋）,and linoleic acid methyl ester were m/z 67（base-peak ion）,220（[M-74]~＋）,263（[M-31]~＋） and 294（M~＋）,according to the fragmentation rules and mass spectrometry characteristics.Oleic acid and linoleic acid isomers had the same characteristics ions respectively,and mass spectrograms were extremely similar.Therefore,it was not effective to analyze the double-bond positions and cis-trans isomersonly by characteristic ions and mass spectrograms.