Influence of acid-base dissociation equilibria during electromembrane extraction

Area of Science:

• Analytical Chemistry
• Separation Science
• Physical Chemistry

Background:

• Electromembrane extraction (EME) is influenced by acid-base and partitioning equilibria.
• Understanding these equilibria is crucial for optimizing EME processes.

Purpose of the Study:

• To develop and experimentally validate a theoretical model for electromembrane extraction.
• To predict extraction efficiency as a function of pH and substance properties.
• To evaluate the model's performance with basic drug substances.

Main Methods:

• Development of a theoretical model for EME.
• Experimental verification using 2-nitrophenyl octyl ether as a supported liquid membrane.
• Extraction of twelve basic drug substances under varying pH conditions.
• Fitting experimental data to the theoretical model.

Main Results:

• The model successfully predicts extraction efficiency based on pH and log P values.
• Substances with log P > 2 are efficiently extracted when acceptor pH < pK_aH - log P.
• Seven of twelve basic drugs fit the model; deviations were observed for substances with log P near 2.0.
• Partition coefficients between 2-nitrophenyl octyl ether and water correlate with traditional log P values.

Conclusions:

• The developed theoretical model provides a reliable method for predicting electromembrane extraction efficiency.
• The model's predictions are generally accurate for basic drugs, with minor deviations attributed to membrane interactions.
• Partition coefficients measured in the EME system are comparable to traditional values, supporting their use in predictive models.