Development and validation of an LC/MS method for the analysis of cholesterol and products of cholesterol oxidation in a new lipid based high cholesterol injectable excipient

Situation: The use of this lipid based excipient system in injectable formulations required a full characterization of its composition.   Lipids are complex multi-component mixtures with very complicated oxidation pathways. In addition most lipids exhibit weak absorptivity and only at low UV wavelengths.  ELSD based detection systems were not able to provide the sensitivity and selectivity required to deal with column-to-column and product lot-to-lot variability.  Tracking of the appropriate peaks in the QC environment was highly problematic.

Task: Develop and validate an LC/MS-based robust methodology for the characterization of cholesterol composition and its degradation products in this new excipient material.

Action: We quickly developed a mass spectrometry compatible chromatographic method. The method employed atmospheric pressure chemical ionization and was able to track five different degradants present in trace levels.  The chromatographic conditions did not require extensive optimization efforts because of the selectivity and sensitivity of selected ion monitoring (SIM) detection. Validation activities demonstrated the robustness of the method.

Result: The developed and validated methodology has provided detailed characterization of this new excipient that addressed the regulatory concerns.