加速溶剂萃取技术提取海洋沉积物中游离态脂肪酸的方法研究

摘要

脂肪酸是沉积物中含量最丰富的脂类标记物之一，其存在形式主要有游离态脂肪酸和结合态脂肪酸。游离态脂肪酸可由溶剂直接提取，结合态脂肪酸是在已提取出游离态脂肪酸的沉积物残渣中加入酸碱加热后再用溶剂提取。加速溶剂萃取技术（ASE ）因成本低和操作毒性小，在脂肪酸研究中得到了广泛的应用。本文采集东海近海海域沉积物作为研究样本，由于其中游离态脂肪酸含量丰富，而结合态脂肪酸含量过低，测定结果精密度差，难以作为方法研究对象，因此主要针对游离态脂肪酸应用ASE 法进行提取，研究了各种实验条件，包括萃取剂、萃取温度、静态萃取时间和循环次数的选择与优化。分析结果表明，甲醇－二氯甲烷（V／V，1∶3）更适合作为萃取剂；随着萃取温度、静态萃取时间、循环次数的增加，不同类型脂肪酸的提取效率各不相同，以涵盖碳原子数最多为先决条件，以脂肪酸的萃取效率最大化为依据，确定了ASE的实验条件是：萃取温度110℃，静态提取时间10 min，循环3次。用这种处理方法5次测定沉积物样品中大部分游离态脂肪酸的精密度为3．3％～19．0％，其替代物回收率为72．2％～104．6％。该方法应用于分析实际海洋沉积物样品，相比于传统的索氏提取法，流程简单，极大地提高了工作效率。%Fatty acids are one of the most abundant lipid markers in marine sediments,whose primary occurrence forms are free fatty acids and conjugated fatty acid.Free fatty acid can be extracted directly by solvent,and conjugated fatty acid is extracted from leftover sediment residue after free fatty acid has been extracted,through adding acid or alkali,and then extracting after being heated.Accelerated Solven Extraction (ASE)is a very popular method in the study of fatty acids due to its low cost and low toxicity.In this study,coastal sediments were collected from the East China Sea.Conjugated fatty acid is not suitable for verifying the method due to its low concentration and large uncertainty;therefore,the determination of free fatty acid in marine sediments by Gas Chromatography-Mass Spectrometry with ASE for sample pretreatment is discussed in this paper.The main factors which affect the extraction yield of fatty acid by ASE,such as the proportion of extractants,the temperature,static extraction time and cycle times are discussed and optimized.The following conclusions were reached:methanol-methylene chloride (V/V=1 ∶3)is more suitable to be the extractant.The extraction efficiency of different types of fatty acids varies with increasing temperature,static extraction time and cycle times.Based on increasing carbons being extracted and the highest extraction efficiency,the optimum parameters for fatty acid extraction from marine sediments are:extraction temperature of 1 1 0℃,static time of 1 0 min and 3 cycles.The precisions of this method were 3.3%to 1 9.0%RSD for most free fatty acids,and the recovery rates were from 72.2% to 1 04.6%.This method is applicable to the quantitative analysis of alcohols and ketones in marine sediment,which is an improvement on conventional Soxhlet extraction with less reagent consumption,good precision and is a simple procedure.