亚麻酸异构体的气相色谱-质谱分析

Analysis of Linolenic Acid Isomers by Gas Chromatography - Mass Spectrometry

摘要:

本文采用气相色谱-质谱法对亚麻酸异构体的出峰顺序和质谱特征进行了分析研究。结果表明：脂肪酸在强极性毛细管柱BPX-70(120 m×0.25 mm×0.25 μm)上的出峰顺序具有一定的规律性，所测亚麻酸异构体中，出峰顺序依次为C18:3 9t，12t，15t、C18:3 9c，12t，15t、C18:3 9t，12c，15t、C18:3 9t，12t，15c、C18:3 9c，12c，15t、C18:3 9c，12t，15c、C18:3 9t，12c，15c和C18:3 9c，12c，15c。根据断裂规律和质谱特征分析，α-亚麻酸甲酯和γ-亚麻酸甲酯的特征离子分别为m/z 79、108(?离子)、236(α离子)、261、292和m/z 79、150(?离子)、194(α离子)、261、292。在8种α-亚麻酸顺反异构体中，当12位双键为顺式时，基峰离子为m/z 79，并具有明显的?离子(m/z 108)和α离子(m/z 236)；而当12位双键为反式时，α离子消失，?离子强度减弱，并表现出离子强度m/z 107>108，且同时当15位双键为反式时，基峰离子为m/z 95；而当15位双键为顺式时，基峰离子为m/z 67。双键位置和顺反构象对亚麻酸的质谱特征产生显著影响，且12位顺反异构的影响大于9位和15位的顺反异构。

Abstract:

The elution order of peaks and the mass spectral features of linolenic acid isomers were studied by gas chromatography-mass spectrometry. The results indicated that there were certain patterns in the elution order of peaks of fatty acids using a strong polar capillary column BPX-70 (120 m × 0.25 mm × 0.25 μm). For the analyzed linolenic acid isomers, the elution order of peaks were C18:3 9t,12t,15t; C18:3 9c,12t,15t; C18:3 9t,12c,15t; C18:3 9t,12t,15c; C18:3 9c,12c,15t; C18:3 9c,12t,15c; C18:3 9t,12c,15c; and C18:3 9c,12c,15c. According to the analyses of fragment patterns and mass spectral features, the characteristic ions of ?-linolenic acid methyl ester were m/z 79, 108 (? ion), 236 (? ion), 261, and 292 and those of γ-linolenic acid methyl ester were m/z 79, 150 (? ion), 194 (? ion), 261, and 292. Among the eight cis and trans isomers of ?-linolenic acid, when there was a cis double-bond at the 12 position, the base-peak ion was m/z 79, and was accompanied by an apparent ? ion (m/z 108) and an ? ion (m/z 236). When there was a trans double-bond at the 12 position, the ? ion disappeared, the ? ion intensity was weakened, and the ion intensity of m/z 107 was greater than that of m/z 108. Additionally, when there was a second trans double-bond at the 15 position, the base-peak ion was m/z 95; however, when there was a second cis double-bond at the 15 position, the base-peak ion was m/z 67. The double-bond positions and cis-trans isomers of linolenic acid have significant impacts on mass spectral features, and the cis and trans isomers at the 12 position show greater influences than those at positions 9 or 15.