title: Interactions of cephalosporins and penicillins with nonpolar octadecylsilyl stationary phase.
abstract: The capacity factors of several penicillins and cephalosporins, as well as those of 7-aminocephalosporanic acid, 6-aminopenicillanic acid, and 7-aminodeacetoxycephalosporanic acid, were determined at pH 2.5-7.5 with different methanol concentrations in the mobile phase. The influence of ionic strength on activity factors also was studied. Some theoretical equations providing a quantitative description of the influence of the mobile phase pH on the retention of penicillins and cephalosporins by an octadecylsilyl stationary phase were established. The analysis of experimental data by a nonlinear least-squares fit to theoretically deduced equations permitted determination of the capacity factors of anionic, cationic, zwitterion, and undissociated forms of the substances studied.
mesh_terms: D002511:Cephalosporins / Q000302:isolation & purification; D055598:Chemical Phenomena; D002621:Chemistry; D002845:Chromatography / Q000379:methods*; D004347:Drug Interactions; D006863:Hydrogen-Ion Concentration; D000432:Methanol; D010406:Penicillins / Q000302:isolation & purification; D012492:Salts; D012821:Silanes; D012825:Silicon; D013329:Structure-Activity Relationship
chemical_list: D002511:Cephalosporins; D010406:Penicillins; D012492:Salts; D012821:Silanes; C024779:octadecylsilane; D000432:Methanol; D012825:Silicon