Solid-state properties hygroscopicity

Among other things, it became established that the nature of the structure adopted by a given compound on crystallization would then exert a profound effect on the solid-state properties of that system. For a given material, the heat capacity, conductivity, volume, density, viscosity, surface tension, diffusivity, crystal hardness, crystal shape and color, refractive index, electrolytic conductivity, melting or sublimation properties, latent heat of fusion, heat of solution, solubility, dissolution rate, enthalpy of transitions, phase diagrams, stability, hygroscopicity, and rates of reactions were all affected by the nature of the crystal structure. 

Solid-state properties (crystalline, not polymorphous, not hygroscopic) that make it a perfect partner for (tablet) compaction. 

Studies of the desolvation of solvatomorphs can be conducted using VT-XRPD. For instance, after the dehydration of a hydrate phase, one may obtain either a crystalline anhydrate phase or an amorphous phase and the XRPD pattern will clearly indicate the difference. In addition, should one encounter an equivalence in powder patterns between the hydrate phase and its dehydrated form, this would indicate the existence of channel-type water (as opposed to lattice boimd water). In one study, the solid-state properties of the isomorphic desolvates of cephalexin, cefaclor, erythromycin A, and spirapril hydrochloride were investigated, with the hygroscopicity of the compounds being evaluated using a vacuum moisture balance and the structural relaxation measured using a combination of VT-XRPD and isothermal microcalorimetry. " ... 

Combination Products. For combination products, additional questions need to be asked such as, Are there any potential chemical reactions between actives and What is the potential impact on physical properties of the product (e.g., hygroscopicity) Therefore, forced degradation of the combined actives in solution and the solid state should be explored to probe all potential modes of degradation. This, in essence, will lead to more stable formulations. 

Polymorphism is an ability of the drug substance to form crystals with different molecular arrangements giving distinct crystal species with different physical properties such as solubility, hygroscopicity, compressibility, and others. This phenomenon is well known within pharmaceutical companies. The reader can find additional information in references 47 and 48. The determination of possible polymorphic transition and existence of thermodynamically unstable forms during preformulation stage of drug development is important. Typical methods used for solid-state characterization of polymorphism are DSC,... 

The ability of many drugs to form salts affords the formulation scientist increased scope to optimize drug product performance. The formation of a drug salt can alter physicochemical properties such as physical and chemical stability, solid state characteristics such as crystal form, melting point, enthalpy, solvation, hygroscopicity, which in turn impact on processability, dissolution rate, and bioavailability, without... 

All the metal-saccharin complexes described here exhibit similar properties. They are found to be non-hygroscopic, stable in air, very soluble in pyridine and N,N-dimethyl formamide, and slightly soluble in cold water. They give almost identical solid state (Nujol) infrared spectra, characteristic peaks of which are 3500-3100 cm 1, s.b[v(0—H) of different types of water molecules present in the complex] 3090 cm 1, s[v(C—H)] 1610 cm , s[v(C=0)] 1570 cm 1, s[v(C—C), mixed with (H—O—H) deformation of lattice water] 1280 cm 1, vs[asymmetric... 

Atmospheric aerosols have a direct impact on earth s radiation balance, fog formation and cloud physics, and visibility degradation as well as human health effect[l]. Both natural and anthropogenic sources contribute to the formation of ambient aerosol, which are composed mostly of sulfates, nitrates and ammoniums in either pure or mixed forms[2]. These inorganic salt aerosols are hygroscopic by nature and exhibit the properties of deliquescence and efflorescence in humid air. That is, relative humidity(RH) history and chemical composition determine whether atmospheric aerosols are liquid or solid. Aerosol physical state affects climate and environmental phenomena such as radiative transfer, visibility, and heterogeneous chemistry. Here we present a mathematical model that considers the relative humidity history and chemical composition dependence of deliquescence and efflorescence for describing the dynamic and transport behavior of ambient aerosols[3]. 

The state of lactose has a major effect on the properties of spray-dried whey powder manufactured by conventional methods, i.e. preheating, condensing to about 50% total solids and drying to less than 4% water. The powder is dusty and very hygroscopic, and when exposed to ambient air it... 

---