Characterisation of instantaneous water absorption properties of pharmaceutical excipients.

Powders absorb water by both capillary imbibition and swelling. The capillary process is almost instantaneous but swelling occurs over a period of time. An isothermal transient ionic current technique was used in this study to characterise the instantaneous absorption properties (rate and capacity) of a few selected pharmaceutical excipients.

A new method of characterising liquid uptake within particles over short time periods.

A method of measuring both the capacity and rate of absorption of liquid by powders of small particles over short time periods (of the order of a few seconds or less) is presented. The method is based on the measurement of the isothermal transient ionic current in a sample cell containing the absorbant material and the liquid. The method has been tested on solid glass beads, porous glass beads and cellulose agglomerates.