James Tam | Authors

A surfactant based diluent was used in sample preparation for reversed phase HPLC analysis of a drug product and its impurities in a phospholipid formulation. The use of the didodecyl trimethylammonium bromide (DDAB) enabled a consistent, quantitative extraction of the analytes of interest from the lipid matrix in a much more aqueous, weak solvent. Water was added as an anti-solvent to precipitate out the surfactant from the system to eliminate HPLC injection pressure spikes, enabling large volume injections and achieving a consistent, robust method for long term use. Method development and validation steps are described.

An unusual source of contamination was found in the reversed-phase LC analysis of a 0.4% (w/w) drug product during the development stability studies at levels much greater than the 4 ppm limit of quantitation. System-related sources (mobile phase, injector carryover and contamination), formulation components (drug substance, excipients), and the sample-handling procedure were studied by a systematic approach. The evaluation of the sample-handling procedure identified extractables from the sample vial (different from that specified in the analytical method) and the rubber-lined vial cap, and incidental transfer of residue from commonly used nitrile gloves as the sources of unintended contamination in sample analysis.