ABSTRACT
Efficiency and Asymmetry...........................................................................301 7.7 Applications in the Pharmaceutical Industry ..............................................304 7.8 Concluding Remarks....................................................................................312 References..............................................................................................................313
Most of the samples analyzed in modern reversed-phase HPLC include ionic or ionizable analytes. While the mechanism of HPLC retention in reversed-phase mode is considered to be competitive hydrophobic interactions of the analyte and organic eluent modifier with the stationary phase, the retention of ionic or ionizable analytes is significantly influenced by other factors such as mobile phase pH, salt type, and salt concentration. Ionic interactions are the strongest among all types of molecular interactions employed in HPLC and even minor variations in reversed-phase HPLC conditions (e.g., concentration of counterions, pH) usually lead to dramatic changes in the retention of ionic analytes.
