The application of a new on-line high-performance liquid Chromatographic method for the clean-up and analysis of drugs in semi-solid formulations was investigated. A short column of a chemically bonded stationary phase (10 μm octadecylsilane) mounted into the sample loop position of the high pressure injection valve was used as the primary clean-up step. The elution behavior of commonly used cream excipients on the loop column as a function of various combinations of water, methanol and THF was studied using a refractive index detector. Typically, samples of the cream were dissolved in methanol-THF and injected onto the loop column. The drug substances were eluted onto the analytical column with predetermined volumes of the mobile phase. The relatively non-polar cream excipients were retained on the loop column. At this time the injection valve was switched, isolating the loop column and the retained excipients were eluted off to waste with a strong solvent (methanol-THF). Loss of efficiency due to the insertion of the loop column was negligible. This technique was applied to the simultaneous analysis of a corticosteroid (hydrocortisone) and a hydrophobic amine (sulconazole nitrate) in a topical cream formulation.
Read full abstract