Surfactant characterization

Surfactants stabilize biomolecules against interfacial stress and/or are prevent adsorption. Polysorbate 20 and 80 (also known as Tween) and poloxamer 188 (e.g. pluronic F68) are so far the only FDA-approved surfactants for parenteral application.

Besides their benefits, it is common knowledge that surfactants, such as polysorbates, are prone to undergo degradation by hydrolysis and oxidation. While such degradation can directly affect the function of the surfactant, it could also lead to the formation of insoluble fatty acid-related particles over time. A potential issue for the safety and efficacy of a biopharmaceutical drug product.

The quality requirements for pharmaceutical grade polysorbate 20 and 80 are specified in the different pharmacopoeias. Further, the ICH countries agree on the key requirements, such as impurity levels and fatty acid composition. For polysorbate 80, the Chinese Pharmacopoeia describes the strictest regulations for the fatty acid composition and requests an all-oleate polysorbate (≥ 98%), whereas the European and US pharmacopoeias specify a purity of ≥ 58% for oleic acid.

Multicompendial surfactants complying all current pharmacopoeias are available. However, their analytical characterization is very challenging due to the structural heterogeneity,  the presence of degradants and other impurities. Coriolis has built up strong expertise and analytical capabilities for surfactant characterization, in particular for the quantification and characterization of polysorbate and polysorbate degradation products.

Due to the lack of chromophores, it is required to either derivatize polysorbate with dyes or use universal detectors such as charged aerosol detectors (CAD), evaporative light scattering detectors (ELSD) or mass spectrometry (MS) in combination with liquid chromatography (LC). For the LC-based methods, it is required to develop sample preparation procedures for protein removal (e.g. organic solvent precipitation) or to isolate polysorbate (e.g. solid phase extraction (SPE))

Various analytical methods are available and required, depending on the scope of the analysis:

• Polysorbate quantification: mixed-mode online SPE or LC-CAD, fluorescence micelle assays, DiI high-throughput quantification assay
• Polysorbate profiling: LC-CAD or LC-MS
• Polysorbate degradation analysis for free fatty acid, oxidation products, POE ester degradation, etc.: LC-MS
• Peroxide assays: Amplex Red, Fox Assay
• Particle characterization methods

List of peer-reviewed journal articles by Coriolis about surfactant characterization:

• Kranz W. et al. Micelle driven oxidation mechanism and novel oxidation markers for different grades of polysorbate 20 and 80. J Pharm Sci 2020 Jun
• Kranz W. et al., Factors Influencing Polysorbate's Sensitivity Against Enzymatic Hydrolysis and Oxidative Degradation. J Pharm Sci. 2019 Jun
• Grabarek A. et al., What makes polysorbate functional? Impact of polysorbate 80 grade and quality on IgG stability during mechanical stress. J Pharm Sci. 2019 Oct
• Martos A. et al., Novel high-throughput assay for polysorbate quantification in biopharmaceutical products by using the fluorescent dye DiI. J Pharm Sci. 2019 Oct
• Martos a. et al., Trends on Analytical Characterization of Polysorbates and Their Degradation Products in Biopharmaceutical Formulations. J Pharm Sci. 2017 Jul

We also offer surfactant characterization services under GMP: Read more