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Updated: May 16, 2026
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Solubility of Hydrophobic Compounds in Aqueous Solution Using Combinations of Self-assembling Peptide and Amino Acid
Published on: September 20, 2017
Solubility-pH profiles of some acidic, basic and amphoteric drugs
Elham Shoghi1, Elisabet Fuguet, Elisabeth Bosch
1Departament de Química Analítica, Universitat de Barcelona, Martí i Franquès 1-11, E-08028 Barcelona, Spain.
Summary
Drug solubility versus pH was determined using shake-flask and Cheqsol methods. Results were consistent, but deviations highlight electrolyte interactions and new species formation, impacting drug solubility profiles.
Area of Science:
- Pharmaceutical Sciences
- Physical Chemistry
Background:
- Understanding drug solubility is crucial for formulation and bioavailability.
- Ionizable drugs exhibit pH-dependent solubility, influenced by their chemical nature.
Purpose of the Study:
- To determine solubility vs. pH profiles for five diverse ionizable drugs.
- To compare the shake-flask (S-F) and Cheqsol methodologies.
- To critically evaluate the influence of buffering electrolytes on solubility measurements.
Main Methods:
- Solubility determination using the classical shake-flask (S-F) method.
- Solubility determination using the potentiometric Cheqsol method.
- Analysis of data using Henderson-Hasselbalch (H-H) or derived equations.
Main Results:
- Consistent solubility profiles were obtained independently from both S-F and Cheqsol methods.
- Deviations from H-H profiles were observed and attributed to specific electrolyte-drug interactions (e.g., hydrotropy).
- Other deviations were linked to the formation of drug aggregates (cefadroxil) or salt precipitation (quetiapine).
Conclusions:
- Both S-F and Cheqsol methods provide reliable drug solubility data.
- Buffering electrolytes can influence solubility measurements through specific interactions.
- Drug aggregation and salt precipitation are critical factors affecting solubility profiles beyond simple ionization.
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