Lecaillon J B, Febvre N, Souppart C
J Chromatogr. 1984 Dec 28;317:493-506. doi: 10.1016/s0021-9673(01)91689-9.
The polarity of a drug is one of the most important parameters for the elaboration of switching systems. If the polarity of the drug is low or medium, "reversed-phase" chromatography is well adapted. The plasma or urine sample is diluted with water, centrifuged and injected first into a column of medium polarity (C2, CN or diol bonded phases). The compounds of interest are stopped on the top of the column and rinsed with water, then eluted and chromatographed on a C8 or C18 analytical column. A third column of still lower polarity can be added to improve the specificity of the system. In each successive step, the polarities of the mobile phases and columns should be decreased to reconcentrate the sample and reduce the band broadening that occurred in the previous step. Compounds of high polarity show almost no retention on reversed-phase columns, and normal-phase chromatography should be used. Aqueous solutions cannot be injected into polar bonded-phase columns as they lead to excessive band broadening. This problem can be solved by diluting plasma or urine with a large volume of a water-miscible organic solvent and injecting the clear supernatant. The compounds to be assayed are first reconcentrated on a polar column (NH2 or N(CH3)2 bonded phase) and then eluted. The selected "heart cut" of the eluate is chromatographed on another, more polar column. The influence of the polarity of drugs on the choice of switching systems is exemplified by assay methods for drugs of low, medium and high polarity.
药物的极性是设计切换系统时最重要的参数之一。如果药物的极性为低或中等，“反相”色谱法就很适用。血浆或尿液样品用水稀释，离心后先注入中等极性的色谱柱（C2、氰基或二醇键合相）。目标化合物停留在柱顶，用水冲洗，然后洗脱并在C8或C18分析柱上进行色谱分析。可以添加第三根极性更低的色谱柱以提高系统的特异性。在每一个后续步骤中，流动相和色谱柱的极性都应降低，以使样品重新浓缩，并减少上一步中出现的谱带展宽。高极性化合物在反相柱上几乎没有保留，应使用正相色谱法。水溶液不能注入极性键合相色谱柱，因为这会导致过度的谱带展宽。这个问题可以通过用大量与水混溶的有机溶剂稀释血浆或尿液并注入澄清的上清液来解决。待分析的化合物首先在极性柱（氨基或二甲基氨基键合相）上重新浓缩，然后洗脱。洗脱液中选定的“中心切割”部分在另一根极性更强的色谱柱上进行色谱分析。低、中、高极性药物的分析方法举例说明了药物极性对切换系统选择的影响。
