Volford O, Takács M, Vámos J
Semmelweis Orvostudományi Egyetem, Gyógyszerészi Kémiai Intézel, Budapest.
Acta Pharm Hung. 1996 May;66(3):133-40.
The properties of silica gel as stationary phase are determined mainly by siloxane, silanol and metal-silanate functional groups. The metals (Na, Ca etc.) getting into the product as trace elements in the course of manufacture may cause the appearance of artefacts. In our previous studies the ion exchange interactions between salt-type analytes and silanol or metal-silanate groups were investigated. It was found in the TLC test of the salts of organic acids and N-bases that the acids and bases are separated from their counter ions and accept protons from or donate to the silica gel layer. In the present paper several analytes of above type have been investigated in situ by remission spectroscopy. These are: phenobarbital, sulfinpyrazone, sulfucetamide, benzoic acid, salicylic acid, (and their Na-salts) and papaverine hydrochloride. Remission spectra were registered from the start spot directly after application and then from the spot after development with the CHCl3EtOH (9 + 1) mobile phase. Based on the difference between the remission spectra of protonated and deprotonated forms of the analytes, the deviations from the initial state could be established. On the basis of the shift of lambda max values one can conclude to the approximate ratio of the protonated (acid) and deprotonated (anion, base) form present in the examined points (middle or edge) of the chromatographic spot. Significantly different protonation states of the analytes were found in the start spots and in the developed spots. These findings are interpreted by the ion exchange interactions between the pharmacon and silica gel. The results provide a deeper insight into the mechanisms of TLC process.
硅胶作为固定相的性质主要由硅氧烷、硅醇和金属硅烷酸盐官能团决定。在制造过程中作为微量元素进入产品的金属（如钠、钙等）可能会导致假象的出现。在我们之前的研究中，研究了盐型分析物与硅醇或金属硅烷酸盐基团之间的离子交换相互作用。在有机酸和N - 碱盐的薄层色谱测试中发现，酸和碱与它们的抗衡离子分离，并从硅胶层接受质子或向硅胶层提供质子。在本文中，通过漫反射光谱对几种上述类型的分析物进行了原位研究。这些分析物包括：苯巴比妥、磺吡酮、磺胺醋酰、苯甲酸、水杨酸（及其钠盐）和盐酸罂粟碱。在点样后直接从起始斑点记录漫反射光谱，然后在用氯仿 - 乙醇（9 + 1）流动相展开后的斑点处记录漫反射光谱。根据分析物质子化和去质子化形式的漫反射光谱之间的差异，可以确定与初始状态的偏差。根据最大吸收波长值的移动，可以推断出在色谱斑点的检测点（中间或边缘）中存在的质子化（酸）和去质子化（阴离子、碱）形式的近似比例。在起始斑点和展开后的斑点中发现分析物的质子化状态有显著差异。这些发现通过药物与硅胶之间的离子交换相互作用来解释。结果为薄层色谱过程的机制提供了更深入的见解。
