Ag^＋-TLC／GC分析食品中的反式脂肪酸

Determination of trans fatty acids in food by Ag^+-TLC/GC

研究了用银离子薄层色谱和气相色谱测定食品中反式脂肪酸组成和含量的方法。采用气相色谱直接分离脂肪酸甲酯时,18∶0~18∶2n-6区域的一些顺、反18∶1异构体和c/t-18∶2异构体的脂肪酸甲酯出峰时间过于接近,部分色谱峰重叠,采用CP-Sil88 100 m极性毛细管柱仍无法完全分离。采用银离子薄层色谱将反式脂肪酸甲酯预分离后,再用气相色谱检测能够避免顺反异构体的色谱峰重叠,可得到更合理的测定结果。实验表明,色谱峰面积和反式脂肪酸浓度的线性关系良好,相对标准偏差为0.29%~0.48%,回收率为92.52%~104.27%。实验测得牛奶和奶油中反式脂肪酸量分别为0.17 g/100 g和5.45g/100 g。11t-18∶1在两样品中含量最高,分别占总反式脂肪酸的38.03%和51.20%。

A method for the determination of composition and contents trans of fatty acids in food with silver ion thin layer chromatography and gas chromatography was set up. The gas chmmatogram region between 18 ： 0 and 18 ： 2n-6 shows many complex mixtures with many overlapping trans-18： 1, c/s-18： 1, and trans/cis-18：2 isomers, which can not be totally resolved by gas chromatography, even if with a highly polar CP-Si188 100m capillary column. A prior separation of these fractions by silver ion thin layer chromatography can give a better analysis of most of the trans-18 ： 1 and c/s-18 ： 1 isomers. It shows that the linear relationship between peak area and concentrations of trans fatty acids was good. The relative standard deviations are 0.29% - 0.48 % ; recoveries are 92.52 % - 106.66%. The trans fatty acids contents in milk and butter are 0.17 g/100 g food and 5.45 g/100 g food respectively, 11t-18：1 are the main components of these samples, accounted for 38.03% and 51.20% of the total trans fatty acid contents respectively.