Validation of an analytical method for the determination of fatty acids in sheep blood serum samples

Low-density dispersive liquid-liquid microextraction with a subsequent esterification step was proposed in this study for the determination of linoleic acid and stearic acid in sheep blood serum samples. The method developed aimed to quickly and efficiently extract and esterify both fatty acids with subsequent analysis by gas chromatography/flame ionization detection. The extraction method was optimized with Scheffé’s polynomial model for three-component mixtures. The method was validated according to the parameters established by Eurachem Guide (2014). The optimal extraction conditions for LD-DLLME were 1400 µL of dispersion medium (MgCl2 0.017%), 400 µL of extractor solvent (toluene) and 1200 µL of dispersion solvent (methanol). The method performance showed adequate selectivity, sensitivity and precision to be applied to real samples, with an average recovery of 98.54% for linoleic acid and 103.83% for stearic acid. LD-DLLME was superior to the traditional method of analysis, which has been used until now for the determination of fatty acids in blood serum samples from ruminants. The analysis of real samples showed that the developed method is efficient for monitoring these substances in ruminants.

本研究提出了结合后续酯化步骤的低密度分散液液微萃取技术，用于测定绵羊血清样品中的亚油酸与硬脂酸。所开发的方法旨在快速、高效地萃取并酯化两种脂肪酸，随后通过气相色谱/火焰离子化检测完成后续分析。本研究采用谢弗（Scheffé）多项式模型对三元混合体系的萃取方法进行了优化。本方法依据《欧洲分析化学合作组织指南（2014）》（Eurachem Guide 2014）中的参数要求完成了方法验证。低密度分散液液微萃取（LD-DLLME）的最优萃取条件为：1400 μL分散介质（0.017%氯化镁溶液）、400 μL萃取溶剂（甲苯）以及1200 μL分散溶剂（甲醇）。该方法的性能表现出良好的选择性、灵敏度与精密度，可适用于实际样品分析，亚油酸的平均回收率为98.54%，硬脂酸的平均回收率为103.83%。LD-DLLME优于目前用于反刍动物血清样品中脂肪酸测定的传统分析方法。实际样品分析结果表明，所开发的方法可有效用于反刍动物体内此类物质的监测工作。