香成分分析中的样品制备技术

综述了几种样品制备技术,包括溶剂萃取、溶剂辅助蒸馏、同时蒸馏萃取、顶空技术和直接热解吸.溶剂萃取操作简单,香味化合物的收率高;但存在许多缺点,如除去溶剂的过程可能会造成许多挥发性成分的损失,萃取物中通常含有高沸点以及非挥发性的成分,对GC仪器造成损害等.蒸汽蒸馏方法制备的样品通常不含高沸点或非挥发性组分,不会对GC造成污染;但一些极性大或亲水的组分不易分离出来.顶空技术快速简单,不需要有机溶剂,需要的样品量少,分离过程中无杂质生成;但由于香味化合物的挥发性不同,顶空中挥发性组分的相对浓度并不反映样品中的香味化合物组成的实际情况.直接热解吸方法简单、快捷,不需要溶剂,一步完成香味化合物的分离和分析,比较适合于固体样品.上述方法各有优缺点,由于香味化合物的复杂性以及产生香味化合物基体的多样性,在研究中这些方法往往相互补充.研究人员应根据分析样品的情况,综合考虑各种因素,选择最适当的方法.

SAMPLE PREPARATION TECHNIQUES IN ANALYSIS OF AROMA COMPOUNDS

Several sample preparation techniques in analysis of aroma compounds were reviewed,including solvent extraction,headspace technique,solid phase microextraction and direct thermal desorption.Solvent extraction usually gives high yields of aroma compounds with easy operation;but there are many disadvantages,such as the loss of more volatile compounds in the process of solvent removal,the contamination of GC due to high-boiling and non-volatile materials in extracts.The samples made by steam distillation do not contain any high-boiling and non-volatile materials and no contaminants are introduced to GC;but highly polar or hydrophilic compounds are not easy to be extracted.Headspace techniques are simple,quick and solventless techniques,and require small amounts of sample without artifacts;but the relative concentration of components in headspace does not reflect the concentration in the sample due to the differences in volatility of aroma compounds.The advantages of the directed thermal desorption are its simplicity and rapidity.Separation and analysis of samples are finished in one step without solvent.It is suitable to solid sample.Each method has both advantages and disadvantages,and they are complementary in research due to the complexity of aroma compounds and versatility of matrix.Researchers should take various factors into account and select the most suitable method according to the samples.