Journal article
Impact of Freeze-Drying on Ionization of Sulfonephthalein Probe Molecules in Trehalose–Citrate Systems
Journal of pharmaceutical sciences, Vol.95(7), pp.1498-1510
07/2006
DOI: 10.1002/jps.20620
PMID: 16721795
Abstract
“pH memory,” i.e., correlation between pH of solution before freeze-drying and chemical reactivity in the freeze-dried state, has been reported in many systems. In this study, the “pH memory” is explored by comparing the extent of protonation of sulfonephthalein probe molecules, bromophenol blue, bromocresol green, and chlorophenol red, in aqueous solution in the pH range of 3.4–6.0 and in the resulting freeze-dried amorphous matrix (lyophile) containing trehalose and sodium citrate buffer. The protonation of the probe molecules was measured in the lyophiles by diffuse reflectance visible spectroscopy, and compared with that in the solution before drying. The protonation of the indicators in the amorphous matrix correlated with solution pH, that is, an increase in solution pH resulted in a progressive decrease in the indicator protonation in the corresponding lyophile. However, the protonation was consistently higher in the lyophile than in the corresponding solution. The Hammett acidity function of lyophiles was calculated based on the extent of protonation of the probe molecules. Protonation of the probe molecules and the Hammett acidity function depended not only on prelyophilization solution pH, but also on the residual water content and the presence of amorphous sugar in the lyophile. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association.
Details
- Title: Subtitle
- Impact of Freeze-Drying on Ionization of Sulfonephthalein Probe Molecules in Trehalose–Citrate Systems
- Creators
- Ramprakash Govindarajan - Department of Pharmaceutics, University of Minnesota, 308 Harvard St. SE, Minneapolis, Minnesota 55455Koustuv Chatterjee - Department of Pharmaceutics, University of Minnesota, 308 Harvard St. SE, Minneapolis, Minnesota 55455Larry Gatlin - Pfizer Global R&D, Groton, Connecticut 06340Raj Suryanarayanan - Department of Pharmaceutics, University of Minnesota, 308 Harvard St. SE, Minneapolis, Minnesota 55455Evgenyi Y Shalaev - Pfizer Global R&D, Groton, Connecticut 06340
- Resource Type
- Journal article
- Publication Details
- Journal of pharmaceutical sciences, Vol.95(7), pp.1498-1510
- DOI
- 10.1002/jps.20620
- PMID
- 16721795
- NLM abbreviation
- J Pharm Sci
- ISSN
- 0022-3549
- eISSN
- 1520-6017
- Publisher
- Elsevier Inc
- Language
- English
- Date published
- 07/2006
- Academic Unit
- Pharmaceutical Sciences and Experimental Therapeutics
- Record Identifier
- 9984065696002771
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