The AAPS Journal

, Volume 16, Issue 5, pp 1128–1131 | Cite as

Light Obscuration Measurements of Highly Viscous Solutions: Sample Pressurization Overcomes Underestimation of Subvisible Particle Counts

  • Daniel Weinbuch
  • Wim Jiskoot
  • Andrea HaweEmail author
Brief/Technical Note


Light obscuration (LO) is the current standard technique for subvisible particle analysis in the quality control of parenterally administered drugs, including therapeutic proteins. Some of those, however, exhibit high viscosities due to high protein concentrations, which can lead to false results by LO measurements. In this study, we show that elevated sample viscosities, from about 9 cP, lead to an underestimation of subvisible particle concentrations, which is easily overlooked when considering reported data alone. We evaluated a solution to this problem, which is the application of sample pressurization during analysis. The results show that this is an elegant way to restore the reliability of LO analysis of highly viscous products without the necessity of additional sample preparation.


high viscosity light obscuration protein formulation subvisible particles 



The authors thank Coriolis Pharma (Martinsried, Germany) for the organizational and financial support, Sarah Zölls for her help regarding project initiation and Partikelmess- und Analysesysteme GmbH (Rutesheim, Germany) for providing the PAMAS SBSS light obscuration system and supporting the analytical work.


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Copyright information

© American Association of Pharmaceutical Scientists 2014

Authors and Affiliations

  1. 1.Coriolis PharmaMartinsriedGermany
  2. 2.Division of Drug Delivery Technology, Leiden Academic Centre for Drug ResearchLeiden UniversityLeidenThe Netherlands

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