气相色谱-质谱联用法检测母乳脂肪中反式脂肪酸

建立了母乳中反式脂肪酸(TFAs)的气相色谱-质谱(GC-MS)检测方法,并应用于母乳脂肪中TFAs的检测。母乳用氨水水解,乙醚和石油醚提取脂肪,提取的脂肪加入C21: 0内标,用三氟化硼甲醇溶液在80℃水浴中冷凝回流15 min进行甲酯化,正己烷提取,上清液用GC-MS分析,内标法定量。在低、中、高加标水平上验证方法的准确度与精密度,结果显示该方法可用于母乳中18种TFAs及其同分异构体的检测,其中12种TFAs在母乳脂肪中的方法检出限为4.0~47.1 mg/kg,回收率为80%~113%, RSD为2.9%~14.5%(n=6)。TFAs在部分母乳脂样品中检出,含量为9.54~6.9 mg/kg。该方法定性、定量准确,可有效用于母乳中TFAs的检测,但仍存在脂肪酸本底干扰等问题,可结合银离子固相萃取柱预分离技术进一步完善。

Determination of trans-fatty acid isomers in human milk fat by gas chromatography-mass spectrometry

A method for the determination of trans-fatty acid isomers in human milk fat was developed by gas chromatography-mass spectrometry (GC-MS), and applied to analyze TFAs in human milk fat. The fat was extracted with diethylether and petroleum ether after ammonia hydrolysis of human milk. C21: 0 internal standard and boron trifluoride methanol solution were added to the extract for fat esterification. The solution then was refluxed in 80℃ water bath for 15 min. Finally the trans-fatty acid methyl ester isomers were extracted with hexane, and analyzed by GC-MS. GC conditions were as follows: an HP-88 column (100 m×0.25 mm×0.2 μ m) with inlet temperature of 260℃, at a split ratio of 10: 1, and a He flow rate of 1 mL/min. The initial column temperature was 140℃ (held for 5 min), then raised up to 240℃ at a rate of 4℃/min (held for 15 min). The electronic ionization (EI) source energy was 70 eV, with auxiliary (AUX) temperature of 280℃, ion source temperature of 230℃, quadrupole temperature of 150℃ in selected ion monitoring (SIM) mode. This method can analyze the 18 TFAs. The method detection limits (MDLs) of 12 TFAs were 4.0-47.1 mg/kg, and the average recoveries were 80%-113% with the relative standard deviation (RSD, n=6) range of 2.9%-14.5%. TFAs were detected in some real samples and the contents were 9.5-46.9 mg/kg. The method is reliable and sensitive, and would be better if the background interference of fatty acids should be diminished by silver ion solid phase extraction.