Amorphous frozen aqueous solution

Fig. 6.1 Mossbauer spectra of an amorphous frozen aqueous solution of 0.03 M Fe(N03)3, obtained at 4.5 K with various applied transverse magnetic fields. The bar diagrams indicate theoretical line positions of the spectral components. The lines are fits to the experimental data. (Reprinted with permission from [12] copyright 1977 by Elsevier)...

Fig. 6.10 Mossbauer spectra of amorphous frozen aqueous solutions with the indicated concentrations of [Fe(H20)6]. The spectra were obtained at 80 K. Rough estimates of the relaxation times are given...

For a batch size of 5 L, 587.5 g (3.2 moles) of mannitol is dissolved in 3.5 L of water. Pamidronic acid (31.6 g, 0.133 moles) is mixed with a 1.0 L aliquot of the mannitol solution to form a slurry. The slurry is then transferred into the remainder of the mannitol solution, and stirred for at least 15 min. Aqueous 1 N sodium hydroxide (270 ml) is then added and the mixture is stirred until a clear, colorless solution results. The pH is then adjusted to 6.50.1 using either 1 M aqueous phosphoric acid or 1 N aqueous sodium hydroxide, as needed. The solution is then filtered through a 0.22 micron filter, and filled at 20°C into vials at 4.0 ml (4.172 g)/vial, under sterile conditions. The aqueous solution is frozen at -37°C and lyophilized (20 mbar, 20°-40°C) to yield 1,250 vials, each containing 30 mg of amorphous disodium pamidronate. The vials are sealed under positive nitrogen pressure. The disodium pamidronate is amorphous (noncrystalline) by X-ray diffraction and contains 0.7 wt-% water. 

Blood plasma was dehydrated from the frozen state under pressures of the order of 0.3 mm. Hg, and temperatures near —30°C. The need for dehydration arose because plasma in aqueous solution spoiled, whereas storing as a dry powder drastically reduced deterioration. Dehydration from the solid state permitted easy re-solution in water or saline solution, by virtue of the high surface-to-volume ratio characteristic of the lyophilic structure produced by this technique. The rigidity of the solid state does not permit substantial shrinkage of the drying material. Dehydration from a liquid solution, on the other hand, is accompanied by excessive volumetric shrinkage, and the result is an amorphous coagulum of low surface-to-volume ratio, and hence poor resolution. Penicillin was dehydrated in very much the same manner, then streptomycin and many other pharmaceutical products were similarly processed. 

Figure 12. Schematic state diagram of temperature vs. w% solute for an aqueous solution of a hypothetical small carbohydrate (representing a model frozen food system), illustrating the critical relationship between Tg and freezer temperature (Tf), and the resulting impact on the physical state of the freeze-concentrated amorphous matrix. (Reproduced with permission from reference 18. Copyri t 1988 Cambridge.)...

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