Investigation of a reverse-phase high performance liquid chromatography (RP-HPLC) method for a weakly basic drug

Formulation development of combination drug products requires the availability of a rapid analytical method with low limits of detection, for the high-throughput analysis of the large number of samples generated. Salmeterol xinafoate (SX) and fluticasone propionate (FP) are coformulated for the treatment of asthma and COPD. RP-HPLC using C- 18 bonded phases of basic compounds, such as SX, can be problematic due to the occurrence of poor peak shapes. This can be overcome by decreasing the flow rate, modifying column temperature, careful selection of the column and use of methanol as organic modifier (McCalley 1999, 2000, 2002). The aim of this study was to examine the performance of SX on a second-generation silica bonded reverse-phase column, with a mobile phase containing a high content of organic modifier.