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

doi:10.3724/SP.J.1123.2016.01003

Abstract

Abstract:

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.

Key words: trans-fatty acids (TFAs), fat, gas chromatography-mass spectrometry (GC-MS), human milk

CLC Number:

O658

LIN Qi, LI Guobo, GE Pin, XU Rongxian, LIN Guobin. Determination of trans-fatty acid isomers in human milk fat by gas chromatography-mass spectrometry[J]. Chinese Journal of Chromatography, 2016, 34(5): 520-527.

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