Contribution to the 4th World Congress on Emulsions Lyon 2006
T. Sobisch, D. Lerche
L.U.M. GmbH, Rudower Chaussee 29 (OWZ), 12489 Berlin, Germany
www.lum-gmbh.com, info@lum-gmbh.de
The development of emulsion based products as well as process development/monitoring and quality assurance require efficient and objective analytical tools for shelf life prediction and stability determination. Freeze/thaw stability is often used as measure of long term stability. On the other hand high freeze/thaw stability is often required as property of the final product. To this end the potential of multisample analytical centrifugation was evaluated as an accelerated test procedure.
A new multisample approach is presented using analytical centrifugation, which allows for an accelerated characterization of destabilization processes (creaming, sedimentation, coalescence, phase separation). The kinetics of these destabilizing processes can be traced simultaneously for up-to 12 different samples with temperature control in the range between 4 and 45 °C. No dilution is necessary, which otherwise could lead to changes of dispersion properties.
Analytical centrifugation measures in a rapid way the inherent stability of the samples. Therefore, alterations due to slow aging may be investigated combining first a shorted common accelerated stability test like freeze/thaw cycling and second a rapid evaluation by analytical centrifugation.
The wide application potential of this approach is demonstrated by examples of measurements on cosmetic creams and on beverages.
1 Introduction
The development of emulsion based products as well as process development/monitoring and quality assurance require efficient and objective analytical tools for shelf life prediction and stability determination. Freeze/thaw stability is often used as measure of long term stability. On the other hand high freeze/thaw stability is often required as property of the final product. To this end the potential of multisample analytical centrifugation was evaluated as an accelerated test procedure.
Multisample analytical centrifugation is efficient in characterization and measurement of the speed of destabilizing processes like creaming, coalescence and phase separation (1-7). It detects very small differences in stability and allows for an accelerated characterization of emulsions without dilution, thus avoiding changes of emulsion properties.
Analytical centrifugation traces the inherent stability, but cannot foresee destabilizing processes that will happen during storage of the sample. But, it will see the results of destabilizing processes far faster than visual observation. Therefore, to this end a combination with suitable stress tests is the method of choice.
As a demonstration the evaluation of aging of cosmetic creams and of beverages is presented, which is important in relation to development of new formulations and in quality control of manufactured products. The stability of samples aged during storage at ambient conditions or by a freeze-thaw cycle (accelerated aging) was compared with the initial stability just after manufacturing.
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