Characterization of polydisperse macrogols and macrogol-based excipients via HPLC and charged aerosol detection

Macrogol-based emulsifiers and their respective precursor substances, i.e. macrogols (PEG), fatty acids (FA), and fatty alcohols (FAA), are widely used excipients which are usually characterized by a series of tests described within the European Pharmacopoeia (Ph. Eur.). Examples are bulk parameters such as the hydroxyl value, the peroxide value, and the determination of fatty acids composition by gas chromatography. The choice of tests depends on the emulsifier considered and its possible precursors. Though all methods are well established, most of them are time consuming and, in some cases, prone to errors and exhibit a low reproducibility. Here, an alternative and supplemental method was developed, using a HPLC-system coupled to a charged aerosol detector (CAD). Seven PEG samples, five saturated as well as two nonsaturated FA samples, and two FAA samples were analyzed. Together with these precursors, 13 macrogol-based emulsifiers of 3 different groups, i.e. macrogol ethers with FAA, macrogol esters with FA, and polysorbates, were successfully analyzed for oligomeric distribution and free precursor molecules in one run.