在线热辅助甲基化-气相色谱法分析棉籽仁中的脂肪酸组成

Analysis of fatty acid composition in cottonseed by gas chromatography with on-line pyrolytic methylation

建立了分析棉籽仁中脂肪酸组成的在线热辅助甲基化-气相色谱法。将0.3 mg棉籽仁样品与2μL三甲基氢氧化硫(0.2 mol/L)加入裂解器,在350℃下进行甲基化反应,通过气相色谱仪进行分离分析,共检测到8种脂肪酸甲酯成分,分别为亚油酸(C18∶2)、油酸(C18∶1)、棕榈酸(C16∶0)、硬脂酸(C18∶0)、肉豆蔻酸(C14∶0)、棕榈油酸(C16∶1)、花生酸(C20∶0)和二十二酸(C22∶0),不饱和脂肪酸的相对含量为66.30%~72.54%,其中亚油酸的相对含量为43.20%~53.61%,相对峰面积的相对标准偏差(RSD)小于10%(n=5)。通过分析5组棉籽仁样品与3种食用油中的脂肪酸组成,结果表明不同产地的棉籽仁中的脂肪酸组成差异不明显,且棉籽仁中的脂肪酸组成与玉米油最为接近,相似度为0.960~0.992。该方法简单、快速、准确,适合分析棉籽仁中的脂肪酸组成。

A method of on-line pyrolytic methylation-gas chromatography was developed for the analysis of fatty acid composition in cottonseed.Fatty acids in cottonseeds were converted to their corresponding fatty acid methyl esters in the presence of trimethylsulfonium hydroxide at 300℃.The major fatty acids were linoleic acid(C18∶2),oleic acid(C18∶1),palmitic acid(C16∶0),stearic acid(C18∶0),myristic acid(C14∶0),palmitoleic acid(C16∶1),arachidic acid(C20∶0)and docosanoic acid(C22∶0).The unsaturated fatty acid content varied from 66.30%to 72.54%,and linoleic acid content varied from 43.20%to 53.61%.The RSDs of the peak areas of the fatty acids were less than 10%(n=5).The fatty acid compositions in the cottonseed samples,obtained from different growing places and different edible oil samples were compared by statistical analysis.The results showed that fatty acid compositions in cottonseed samples from different regions were similar.The fatty acid composition in cottonseed samples was closest to that of corn oil,and the similarity varied from 0.960 to 0.992.The method is simple,rapid,accurate,and is suitable for the analysis of fatty acid composition in cottonseed.