Retention behaviour in micro-HPLC on various types of glasses modified with phenyl groups

The retention and selectivity behaviour of some antiepileptic drugs were studied by micro high-performance liquid chromatography on nine types of phenyl-modified glasses, prepared with xylene solution containing phenyldimethylchlorosilane (P), diphenylmethylchlorosilane (D) or triphenylchlorosilane (T), using three types of glass with various mean pore diameters and/or specific surface areas. From elemental analysis data for carbon, the maximum number of accessible phenyl surface groups per 100A2 of glass (mean pore diameter: 335A, specific surface area: 69m2/g) in P, D and T gel was calculated to be 2.38, 1.58 and 0.76, respectively. Using various CH3CN−0.01 M KH2PO4 mixtures as eluents, the antiepileptic drugs were separated on all the glasses studied, but with different degrees of resolution. With an increase in the specific surface area, the k′ values of some antiepileptic drugs also increased.