Water activity, or equilibrium relative humidity( ERH%), is widely used as a quality control measure in pharmaceuticals to maintain stability of the composition and effectiveness of the active ingredients (API).
By controlling water activity , especially of film coated tablets, the product shelf-life may be maximised especially with respect to the micro-climate humidity that is created inside the blister packaging during transportation and use in many different climate conditions globally.
API effectiveness may be maximised and maintained during process drying where sample water activity may be controlled right through to filmcoating and packaging.
Normally, very low water activity control measures for pharmaceuticals are needed which mean that measuring instruments require calibration at ultra –low humidity levels with reliable traceable standards. Often there are also high-solvent contents in samples which necessitate specific filters for the sensor cell to protect it from contamination and consequent calibration drift. These special REDOX filters act as a barrier to allow only water molecules to pass through to the sensor cell and give reliable readings.