气相色谱测定牦牛骨中脂肪酸的甲酯化方法比较

Comparison of the methylation methods for the determination of fatty acids in Yak bones by gas chromatography

利用气相色谱（GC）技术,采用酸水解提取脂质,比较了 6种甲酯化法（乙酰氯-甲醇法、 H2SO4 -甲醇法、 HCl- 甲醇法、 KOH-甲醇法、 KOH-甲醇＋H2 SO4 -甲醇法和KOH-甲醇＋HCl-甲醇法）对脂肪酸测定的影响,优选牦牛骨中脂 肪酸测定的最佳方法.37种脂肪酸标准样品在0. 28～ 250. 00 mg/L范围内线性关系良好,相关系数均大于0. 99 （除 C4：0外）.碱酯化法和酸碱结合法几乎无法测出牦牛骨中的脂肪酸,其测得的总脂肪酸含量小于0. 20 g/100 g.乙酰氯-甲醇法测得的总脂肪酸含量（13. 61 g/100 g ）显著高于H2 SO4 -甲醇法（总脂肪酸含量为11. 68 g/100 g ） 和 HCl-甲醇法（总脂肪酸含量为3. 18 g/100 g ）测得的结果.乙酰氯-甲醇法和H2 SO4 -甲醇法的日内和日间精密度 分别为0. 27%-8. 60%和0. 34%-2. 64%,两种方法中脂肪酸的回收率为83. 06% - 105. 54%.结果表明,酸水解-乙 酰氯-甲醇法是牦牛骨中脂肪酸测定的最佳方法.C18： 1n9c、C16 ： C18：0和共轭亚油酸（ CLA）是牦牛骨的主要 脂肪酸,其总和达脂肪酸总量的85% 以上,饱和脂肪酸与不饱和脂肪酸含量比值约为1：2.牦牛骨中脂肪酸的研究 为骨资源脂质的有效利用提供了重要依据.

The acid hydrolysis-esterification system with six methylation methods （ acetyl chlo-ride-methanol method, H2SO4-methanol method, HCl-methanol method, KOH-methanol method, KOH-methanol＋H2SO4-methanol method and KOH-methanol ＋ HCl-methanol method） were compared for the fatty acids （FAs） profiling of Yak bones by gas chromatography （ GC） in this study. Good linearities were obtained in the range of 0. 28-250. 00 mg/L with correlation coefficient R2〉0. 99,except for C4：0 （R2 = 0.987 8）. FAs can hardly be detected by the base- catalytic method and the combined acid-base method （ the content of total FAs was less than 0. 20 g/100 g ） in the present study. The FAs determined by the acetyl chloride-methanol method （content of total FAs was 13. 61 g/ 100 g ） was superior to the H2SO4-methanol method （ content of total FAs was 11. 68 g/ 100 g ） and the HCl-methanol method （ content of total FAs was 3. 18 g/100 g ）. The precisions for intra-day and inter-day of acetyl chloride-methanol method and H2SO4-methanol method were 0. 27% - 8. 60% and 0. 34% - 2. 6 4 %, respectively. And the recoveries for the FAs of these two methods were in the range of 83. 0 6 % -105. 54%. This study suggested that the acid hydrolysis-acetyl chloride-methanol method was the best method in the six methods. It was convenient for the accurate determination of FAs in Yak bones. C18 ：1n9c, C16：0, C18：0 and conjugated linoleic acid （CLA） were the mainly FAs in Yak bones,and the sum of the four FAs was more than 85% of the total FAs. The ratio of the contents of the saturated and unsaturated FAs in Yak bones was about 1 ：2. The study of fatty acids in Yak bones provides an important basis for the effective utilization of bone resources.