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Calculating critical relative humidity from solubility according to nonelectrolyte Wilson nonrandom factor model
Lin Luo1, Yingli Wang, Xiancheng Zhan
1Key Laboratory of Drug Targeting, West China School of Pharmacy, Sichuan University , Chengdu, Sichuan, P.R. China.
Drug Development and Industrial Pharmacy
|December 22, 2011
Summary
This study determined the critical relative humidity for 25 substances using air humidity equilibrium. Calculated values closely matched experimental results, validating theoretical models for predicting drug stability.
Area of Science:
- Physical Chemistry
- Pharmaceutical Sciences
- Materials Science
Background:
- Understanding critical relative humidity (H(cr)) is crucial for predicting the stability and hygroscopicity of drugs and chemicals.
- The air humidity in equilibrium (AHE) method is a standard technique for determining H(cr).
- Predictive models can potentially streamline the assessment of material stability.
Purpose of the Study:
- To determine the critical relative humidity (H(cr)) for 25 diverse drugs and chemicals.
- To investigate the theoretical relationship between H(cr) and the solubility of these substances.
- To evaluate the accuracy of predictive models (N-Wilson-NRF and Raoult's law) for H(cr).
Main Methods:
- Determination of H(cr) using the air humidity in equilibrium (AHE) method for 25 compounds.
- Theoretical exploration of the correlation between H(cr) and compound solubility.
- Calculation of H(cr) based on solubility data using the nonelectrolyte Wilson nonrandom factor (N-Wilson-NRF) model and Raoult's law.
Main Results:
- Experimental H(cr) values were successfully obtained for 25 drugs and chemicals.
- A theoretical relationship between H(cr) and solubility was established.
- Calculated H(cr) values derived from solubility using the N-Wilson-NRF model and Raoult's law showed good agreement with experimentally measured values.
Conclusions:
- The air humidity in equilibrium (AHE) method effectively determines the critical relative humidity of pharmaceutical compounds.
- Theoretical models, specifically the N-Wilson-NRF model and Raoult's law, can accurately predict H(cr) from solubility data.
- These findings support the use of solubility-based calculations for predicting drug hygroscopicity and stability, aiding in formulation development.
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