for Physical Chemists by Physical Chemists


High throughput screening of pKa by capillary electrophoresis and mass spectrometry and long-term validation

Hong Wan1, Anders G. Holmén1, Yudong Wang3, Walter Lindberg1, Marie Englund1, Mats B. Någård2, Richard A. Thompson2
AstraZeneca R & D, S-43183 Mölndal, Sweden 1Lead Generation, DMPK & Physical Chemistry 2DMPK and Bioanalytical Chemistry 3Pharmaceutical & Analytical R&D

In this talk, I will present a high throughput pKa screening method based on pressure-assisted capillary electrophoresis (CE) and mass spectrometry (MS) which has been developed and successfully implemented in drug discovery in AstraZeneca, Mölndal. The method consists of a series of volatile buffers covering a pH range from 2.3 to 10.7 with the same ionic strength employed for effective mobility measurement by CE/MS. The pKa values of compounds can be obtained by non-linear fit of effective mobility as a function of pH. In general, the CE/MS system provides a 10-fold higher sensitivity than UV detection, enabling direct screening of poorly soluble compounds. The newly developed CE/MS method offers high throughput capacity by pooling a number of compounds into a single sample. Simultaneous screening of more than 50 compounds was achieved in less than 150 min. The measured pKa values by CE/MS are consistent with published data obtained from the CE/UV method and are also in good agreement with data generated by other methods. I will also demonstrate the long-term validation and performance of our pKa assay including the on-line reference control. The accuracy and reproducibility of the method as well as automated data analysis will be presented and compared with CE/UV and traditional titration methods.

Key references:
1. Wan, H.; Holmén, A. G.; Wang, Y. D.; Lindberg, W.; Englund, M. Någård, M.; Thompson, R. High-throughput screening of pKa, values of pharmaceuticals by pressure-assisted capillary electrophoresis and mass spectrometry. Rapid Communications in Mass Spectrometry 2003, 17, 2639-2648.
2. Wan, H.; Holmén, A.; Någård, M.; Lindberg, W. Rapid screening of pKa values of pharmaceuticals by pressure-assisted capillary electrophoresis combined with short-end injection. Journal of Chromatography 2002, A. 979, 369-377.

Dr. Hong Wan is Principle Scientist at AstraZeneca R&D Mölndal, Lead generation, DMPK & Physical Chemistry. He received his Ph.D. in Analytical Chemistry, Stockholm University in 1996 and honoured as Associate Professor in Karlstad University, Chemistry Dept. 2002. He joined AstraZenaca, Physical Chemistry group in 2001. His recent new developments and interest include high-throughput screening of pKa, plasma protein binding and tissue binding. He is the author and co-author of nearly 50 publications including several invited reviews. He is currently Editorial board member for Expert Opinion on Drug Metabolism and Toxicology and The Open Spectroscopy Journal.

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Last modified: 28 April 2008