Hlongwane C, Delves I G, Wan L W, Ayorinde F O
Department of Chemistry Howard University, Washington, DC 20059, USA.
Rapid Commun Mass Spectrom. 2001;15(21):2027-34. doi: 10.1002/rcm.462.
Quantitative analyses of fatty acids from five triacylglycerol products, coconut oil, palm kernel oil, palm oil, lard and cocoa butter, were carried out using two analytical methods: matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and gas chromatography (GC), in an effort to validate the application of MALDI-TOFMS in quantitative fatty acid analysis. For the GC analysis, transmethylated products were used, whereas, for the MALDI-TOF analysis, saponified products were used. Under MALDI-TOF conditions, the acids were detected as sodiated sodium carboxylates RCOONa + Na consistent with the mode of ionization that was previously reported. Thus, the MALDI-TOF mass spectrum of saponified coconut oil showed the presence of sodiated sodium salts of caprylic acid (7.5 +/- 0.67, m/z 189), capric acid (6.9 +/- 0.83, m/z 217), lauric acid (47.8 +/- 0.67, m/z 245), myristic acid (20.4 +/- 0.51, m/z 273), palmitic acid (9.8 +/- 0.47, m/z 301), linoleic acid (0.9 +/- 0.07, m/z 325), oleic acid (4.8 +/- 0.42, m/z 327) and stearic acid (2.0 +/- 0.13, m/z 329). Saponified palm kernel oil had a fatty acid profile that included caprylic acid (3.5 +/- 0.59), capric acid (4.7 +/- 0.82), lauric acid (58.6 +/- 2.3), myristic acid (20.9 +/- 1.5), palmitic acid (7.2 +/- 1.1), oleic acid (3.8 +/- 0.62) and stearic acid (1.2 +/- 0.15). Saponified palm oil gave myristic acid (0.83 +/- 0.18), palmitic acid (55.8 +/- 1.7), linoleic acid (4.2 +/- 0.51), oleic acid (34.5 +/- 1.5), stearic acid (3.8 +/- 0.26) and arachidic acid (0.80 +/- 0.22). Saponified lard showed the presence of myristic acid (1.5 +/- 0.24), palmitic acid (28.9 +/- 1.3), linoleic acid (13.7 +/- 0.67), oleic acid (38.7 +/- 1.4), stearic acid (12.8 +/- 0.64) and arachidic acid (2.4 +/- 0.35). Finally, for saponified cocoa butter, the fatty acid distribution was: palmitic acid (32.3 +/- 1.0), linoleic acid (2.6 +/- 0.35), oleic acid (34.9 +/- 1.7) and stearic acid (30.3 +/- 1.6). Quantitative gas chromatographic analysis of the corresponding methyl esters from these triacylglycerol products yielded data that were mostly in agreement with the MALDI-TOFMS data. The MALDI-TOF experiment, however, proved to be superior to the GC experiment, particularly with regard to baseline resolution of unsaturated acids. Furthermore, the ability of MALDI-TOFMS to detect low concentrations of fatty acids rendered it more sensitive than the GC methodology.
采用两种分析方法对五种三酰甘油产品（椰子油、棕榈仁油、棕榈油、猪油和可可脂）中的脂肪酸进行了定量分析，这两种方法分别是基质辅助激光解吸/电离飞行时间质谱法（MALDI-TOFMS）和气相色谱法（GC），目的是验证MALDI-TOFMS在脂肪酸定量分析中的应用。对于GC分析，使用的是甲酯化产物，而对于MALDI-TOF分析，使用的是皂化产物。在MALDI-TOF条件下，检测到的酸为羧酸钠盐RCOONa + Na，这与先前报道的电离模式一致。因此，皂化椰子油的MALDI-TOF质谱显示存在辛酸（7.5 +/- 0.67，m/z 189）、癸酸（6.9 +/- 0.83，m/z 217）、月桂酸（47.8 +/- 0.67，m/z 245）、肉豆蔻酸（20.4 +/- 0.51，m/z 273）、棕榈酸（9.8 +/- 0.47，m/z 301）、亚油酸（0.9 +/- 0.07，m/z 325）、油酸（4.8 +/- 0.42，m/z 327）和硬脂酸（2.0 +/- 0.13，m/z 329）的钠皂化盐。皂化棕榈仁油的脂肪酸谱包括辛酸（3.5 +/- 0.59）、癸酸（4.7 +/- 0.82）、月桂酸（58.6 +/- 2.3）、肉豆蔻酸（20.9 +/- 1.5）、棕榈酸（7.2 +/- 1.1）、油酸（3.8 +/- 0.62）和硬脂酸（1.2 +/- 0.15）。皂化棕榈油含有肉豆蔻酸（0.83 +/- 0.18）、棕榈酸（55.8 +/- 1.7）、亚油酸（4.2 +/- 0.51）、油酸（34.5 +/- 1.5）、硬脂酸（3.8 +/- 0.26）和花生酸（0.80 +/- 0.22）。皂化猪油显示存在肉豆蔻酸（1.5 +/- 0.24）、棕榈酸（28.9 +/- 1.3）、亚油酸（13.7 +/- 0.67）、油酸（38.7 +/- 1.4）、硬脂酸（12.8 +/- 0.64）和花生酸（2.4 +/- 0.35）。最后，对于皂化可可脂，脂肪酸分布为：棕榈酸（32.3 +/- 1.0）、亚油酸（2.6 +/- 0.35）、油酸（34.9 +/- 1.7）和硬脂酸（30.3 +/- 1.6）。对这些三酰甘油产品相应甲酯进行的气相色谱定量分析得到的数据大多与MALDI-TOFMS数据一致。然而，MALDI-TOF实验被证明优于GC实验，特别是在不饱和酸的基线分辨率方面。此外，MALDI-TOFMS检测低浓度脂肪酸的能力使其比GC方法更灵敏。
