Horman I, Traitler H
Nestlé Research Centre, Nestec Ltd., Lausanne, Switzerland.
Biomed Environ Mass Spectrom. 1989 Nov;18(11):1016-22. doi: 10.1002/bms.1200181111.
About 60 long-chain fatty acids occur naturally in lipids of biological tissues and fluids, oils, fats and waxes. The ion trap detector (ITD) offers a convenient but powerful means for the routine analysis by gas chromatography/mass spectrometry of such fatty acids as their methyl esters (FAMES). Enhanced [M + 1]+ ions may be formed at higher sample levels of 50 ng or more. However, spectra still retain a predominantly electron impact (EI) character. Using the classical mass spectral performance test compound methyl stearate as an example, good library comparisons were obtained for spectra run over a dynamic range of 2 pg to 225 ng, when a mid-range ITD spectrum run on 7.5 ng was used as a reference. Almost equally good spectral comparisons were found with literature reference spectra run on both quadrupole and sector conventional mass spectrometers. Using human plasma phospholipid FAMES as an example, along with an ITD-generated EI spectral library of FAMES standards, it was seen that for most of the components present the mass spectral library comparison was good enough to permit identification based on mass spectrometry alone. For all components, a combination of gas chromatographic retention index and mass spectral information permitted an unequivocal identification.
生物组织和体液、油类、脂肪及蜡质的脂质中天然存在约60种长链脂肪酸。离子阱检测器（ITD）为通过气相色谱/质谱对这些脂肪酸的甲酯（FAMES）进行常规分析提供了一种便捷而强大的手段。在50 ng或更高的较高样品水平下可能会形成增强的[M + 1]+离子。然而，光谱仍主要保留电子轰击（EI）特征。以经典的质谱性能测试化合物硬脂酸甲酯为例，当将在7.5 ng上运行的中等范围ITD光谱用作参考时，在2 pg至225 ng的动态范围内运行的光谱可获得良好的谱库比对结果。在四极杆和扇形传统质谱仪上运行的文献参考光谱也发现了几乎同样好的光谱比对结果。以人血浆磷脂FAMES为例，连同ITD生成的FAMES标准品EI光谱库一起，可以看出，对于大多数存在的组分，质谱库比对足够好，仅基于质谱就可以进行鉴定。对于所有组分，气相色谱保留指数和质谱信息的结合允许进行明确的鉴定。
