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用一般的色谱固定液不能将八碳芳烃异构体中的间位和对位二甲苯很好地分开。含有长链脂肪族胺的有机粘土可以达到这个目的,但是它却不能分离乙苯和对二甲苯,同时邻二甲苯在间二甲苯之前流出。十八烷可以很好地分离乙苯和对二甲苯,但邻二甲苯在间二甲苯以后流出,而且它对于邻二甲苯的滞留作用不强。邻苯二甲酸二壬酯虽然对于乙苯和对二甲苯分离的作用不大,但对于邻二甲苯有较强的亲和力。因此,将上述三者适当地配合可以将八碳芳烃的四个异构体很好地分开。采用串联柱或混合固定液都可以达到上述目的。
With conventional chromatographic fixatives, the meta and para xylene in the octa-aromatics isomers can not be well separated. Organic clays containing long-chain aliphatic amines can do this, but they can not separate ethylbenzene and para-xylene while o-xylene elutes before meta-xylene. Octadecane separates ethylbenzene and para-xylene well, but o-xylene elutes after meta-xylene, and its retention on o-xylene is not strong. Dinonyl phthalate has little affinity for the separation of ethylbenzene and para-xylene, but has a stronger affinity for o-xylene. Accordingly, the four isomers of octa-aromatics can be well separated by appropriately combining the three. This can be accomplished by using tandem columns or mixed fixatives.