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Solvation in hydrofluoroalkanes: How can ethanol help?
Denise S Conti1, Jordan Grashik, Lin Yang
1Department of Chemical Engineering and Materials Science, College of Engineering, Wayne State University, Detroit, MI, USA.
The Journal of Pharmacy and Pharmacology
|August 14, 2012
Summary
Ethanol enhances solvation in hydrofluoroalkane (HFA) mixtures for pressurized metered-dose inhalers (pMDIs). It significantly improves solvation for ester and ether moieties, but offers limited benefits for alkyl groups.
Area of Science:
- Pharmaceutical Science
- Physical Chemistry
- Materials Science
Background:
- Pressurized metered-dose inhalers (pMDIs) utilize hydrofluoroalkanes (HFAs) as propellants.
- Optimizing drug solvation within HFAs is crucial for pMDIs efficacy.
- Ethanol is a potential cosolvent for modifying HFA properties.
Purpose of the Study:
- To assess ethanol's capacity to enhance the solvation of various chemical moieties within HFA-mimicking solvents.
- To quantify the impact of ethanol concentration on solvation properties relevant to pMDIs.
Main Methods:
- Chemical force microscopy (CFM) was employed to measure adhesion forces (F(ad)) between different molecular interactions (alkyl, ether, ester).
- Experiments were conducted using 2H,3H-perfluoropentane (HPFP), a liquid simulating HFA propellants, mixed with varying ethanol concentrations.
- Johnson-Kendall-Roberts (JKR) theory was applied to model the experimental adhesion force data.
Main Results:
- The addition of ethanol decreased normalized adhesion forces (F(ad)/R), indicating improved solvation.
- At 15% ethanol (v/v), solvation enhancement was observed: 34% for alkyl, 63% for ether, and 67% for ester moieties.
- The solvation capability followed the order: ester > ether > alkyl.
Conclusions:
- Ethanol provides limited solvation enhancement for alkyl moieties in HFA-based systems.
- Significant improvements in solvation were observed for ether-based and ester-based moieties.
- Ethanol shows potential as a cosolvent for pMDIs formulated with amphiphiles containing ether or ester groups.
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