Non-Invasive, Continuous, Quantitative Detection of Solvent Content in Vacuum Tray Drying

Area of Science:

• Pharmaceutical Science
• Chemical Engineering
• Analytical Chemistry

Background:

• Monitoring residual solvents in pharmaceutical powders is crucial for product quality and safety.
• Current indirect methods like mass spectrometry have limitations, including probe fouling and delayed results.

Purpose of the Study:

• To develop and validate a non-invasive in situ capacitance instrument for continuous monitoring of residual solvents in pharmaceutical powders during vacuum drying.
• To model vapor sorption kinetics and electric field interactions for improved understanding and application of the technique.

Main Methods:

• Embedding a capacitance instrument in a vacuum-drying tray base.
• Validating the instrument with Microcrystalline Cellulose and spray-dried Copovidone powder containing water and water/acetone mixtures.
• Developing a vapor sorption model to analyze kinetic and diffusion limits based on powder thickness.
• Modeling the electric field to interpret signals related to solvent mass fraction.

Main Results:

• The capacitance instrument successfully monitored residual solvent content in real-time.
• Vapor sorption modeling revealed kinetic limits for thin powder layers and diffusion limits for thicker layers.
• The developed model aids in interpreting capacitance signals for variable solvent content.

Conclusions:

• The non-invasive capacitance instrument provides a reliable and advantageous in situ method for monitoring residual solvents in pharmaceutical powders.
• This technique offers real-time data, avoiding issues associated with indirect methods and probe fouling.
• The study provides a foundation for designing and implementing this technology in pharmaceutical manufacturing.