Moisture and density measurements in powders: from geophysics to pharmacy

The quality of pharmaceutical powders depends on fine control of their density and moisture content. Meanwhile, their processing requires availability of non-invasive instrumentation. We exploit recent advances in quantitative measurements of complex dielectric permittivity in hyper-arid desert sands to design capacitance instruments that can detect subtle changes in density and moisture in pharmaceutical processes and storage. We illustrate the technique with measurements of non-linear moisture diffusion through an excipient powder.