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Diclofenac sodium Many powdery solids tend to adsorb moisture(deliquescence) or form pseudopolymorphs (solvates). Diclofenac sodium shows no tendency to bind water at 40°C up to a relative humidity of 50%. At a relative humidity of 75%, however, a water absorption of 29% occurs. If the moisture content of the sample atmosphere is then reduced again to 5%, the release of water can be observed by means of the TG signal; the reversibility of the water absorption can thereby be confirmed. The exposure of active ingredients and formulations at 40°C and a relative humidity of 75% serves for testing storage stability in climates with high humid- ity. In both research and production related monitoring, it is important to analyze properties such as melting behavior, purity,thermal stability, decomposition behavior and the absorption of moisture during storage. The following examples show the versatile possibilities for employing thermal analysis instrumentation in pharmaceutical applications. -Lactose monohydrate By investigating -lactose monohydrate with the STA449 Jupiter
® , simultaneous TG and DSC data can beobtained with one measurement. By the mass loss of4.91% along with the endothermal signal at 144°C,dehydration of -lactose mono-hydrate to water-free -lactose. The energetic effects at 165°C and 171°C,however, are not connected with a mass change andcan therefore be interpreted as structural phase transitions. The decomposition is shown by the massloss in the TG curve and already starts at the begin- ning of the melting process of water-free -lactose. 9