Study of the retention behaviour of barbiturates by overpressured layer chromatography using silica gel bonded with tricaprylmethylammonium chloride

Abstract

The chromatographic behaviour of twelve barbituric acid derivatives was studied by overpressured layer chromatography using silica gel impregnated with tricaprylmethylammonium chloride (TCMA). The retention of the barbiturates decreased with increasing TCMA concentration on the layer. The R F values increased with increasing methanol content of the eluent. The pH and the inorganic salt concentration in the eluent had no effect on the retention. Similar results were obtained earlier for different types of compounds, e.g., amino- and nitrosalicylic acids, pyrimidine derivatives, penicillins, cephalosporins and tetracyclines. Several similarities have been observed between chromatographic processes performed either on silica gel layers or on a dynamically modified silica high-performance liquid chromatographic column with eluents containing an ion-pairing reagent. It has been shown that no ion pairing occurs on silica gel layers impregnated with TCMA. Hydrophobic interactions play an important role in the retention of the compounds. The retention is controlled by the TCMA adsorbed on the silica gel layer. The results of the best separations are given.