Impedance spectroscopy for multi-state analysis of dissolvable powders: Determining layer thickness and moisture content

This study presents a novel methodology for applying Electrical Impedance Spectroscopy to analyze the electrical properties of dissolvable powders, when applied as a coating layer to quantify their thickness and moisture content. To address challenges posed by undefined geometries, powders were dissolved and applied as coatings on custom-designed Printed Circuit Board electrodes. Using sodium benzoate as a model material, the drying process was monitored in off-line measurements, revealing distinct transitions in electrical properties. Impedance and phase angle measurements effectively tracked moisture reduction during drying, while coating thickness and solution concentration also influenced conductivity. The findings demonstrate the potential of this approach for industrial applications, such as fluidized bed spray granulation, by enabling real-time monitoring of drying states. • Developed a novel method for coating layer characterization using IS. • Correlated moisture content and coating layer thickness to electrical properties. • Demonstrated potential for monitoring of fluidized bed spray granulation.