Direct and Accelerated Characterization of Formulation Stability

Abstract

Formulation of products as well as process and quality control is in need of fast and efficient measurement techniques of the state of dispersion products. We review the basics of experimental techniques of stability assessment of suspensions and emulsions, procedures of accelerated stability testing, and discuss the relationship between results of “accelerated” tests and the outcome under normal conditions of storage and usage (shelf life). Experimental results of the accelerated formulation testing are given with the focus on optical methods measuring stability based on space and time resolved changes of the volume concentration within the entire sample (STEP-Technology). In particular, acceleration of stability assessment acceleration by inclination and analytical centrifugation is demonstrated for diverse types of formulations. If the rate limiting step of destabilization is not sedimentation or creaming a combination with other established aging tests (temperature storage, freeze-thaw-cycles, physicochemical conditions, etc.) is suggested to reduce evaluation time.

Keywords:

• Aging tests
• analytical centrifugation
• dispersion stability
• inclined settling
• shelf life

Acknowledgments

This study was supported in part by grants from the Bundesministerium für Wirtschaft und Technology (Proinno II KA 0047301 AWZ3; Inno-Watt 082075). The authors thank Dipl.-Ing. T. Detloff for helpful discussions and editing the figures.

Notes

From the Proceedings from Formula VI in Stockholm 2010.