Solubility, Opalescence, and Particulate Matter

  • Hanns-Christian MahlerEmail author
  • Anja MatterEmail author
Part of the AAPS Advances in the Pharmaceutical Sciences Series book series (AAPS, volume 38)


“Appearance” is an analytical test often found in specifications of protein drug products. However, appearance can mean many different things, including dosage form (liquid, dried), color (coloration of solution, color of cake), cake appearance (in case of a lyophilisate), opalescence, or turbidity, and—in some cases—even visible particles. “Maximum solubility” is a parameter that has been previously evaluated for proteins. But given the nature of biologics and the analytical methods used for assessing solubility often do not yield any practically relevant information. Opalescence, respectively, solution clarity can be measured as defined by the European Pharmacopeia. It is a helpful parameter that can relate to aggregation, but also other solution phenomena like liquid phase separation. The coloration of solution is also defined in the European Pharmacopeia. Coloration in protein products can relate to concentration, type of formulation, but also process- or product-related degradants or contaminants. Solution viscosity is of utmost importance for manufacturing as well as administration of biologics at higher concentration. Finally, aggregates and particles can arise as a result of degradation pathways and subvisible and visible particles in parenteral preparations also have to comply with related pharmacopoeial requirements.


Solubility Opalescence Turbidity Aggregates Particles Visible particles Subvisible particles Submicron particles Viscosity High-concentration formulations Color Appearance 


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Copyright information

© American Association of Pharmaceutical Scientists 2018

Authors and Affiliations

  1. 1.Lonza AG, Drug Product ServicesBaselSwitzerland

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