Freeze-drying characterization

Carpenter, J.F., Crowe, L.M. Crowe, J.H. (1987). Stabilization of phosphofruc-tokinase with sugars during freeze drying characterization of enhanced protection in the presence of divalent cations. Biochimica Biophysica Acta, 923, 109-15. 

Therefore, freeze-drying should be carried out at the highest allowable product temperature that maintains the appropriate attributes of a freeze-dried product. This temperature depends on the nature of the formulation. Process development and validation requires characterizing the physical state of the solute, or solutes, that result from the freezing process and identifying a maximum allowable product temperature for the primary drying process [20,21]. 

Packets of instant coffee proudly proclaim that the product has been freeze-dried . In practice, beans of coffee are ground, boiled in water and filtered to remove the depleted grounds. This process yields conventional fresh coffee, as characterized by its usual colour and attractive smell. Finally, water is removed from the coffee solution to prepare granules of instant coffee. 

Negative atmospheric pressure chemical ionization (APC) low-energy collision activation mss spectrometry has also been employed for the characterization of flavonoids in extracts of fresh herbs. Besides the separation, quantitative determination and identification of flavonoids, the objective of the study was the comparison of the efficacy of the various detection systems in the analysis of flavonoids in herb extracts. Freeze-dried herbs (0.5g of chives, cress, dill, lovage, mint, oregano, parsley, rosemary, tarragon and thyme) were ground and extracted with 20 ml of 62.5 per cent aqueous methanol. After sedimentation the suspension was filtered and used for HPLC analyses. Separations were carried out in an... 

Amination (11) and solution carbonation (8) reactions were carried out as described previously. For solid-state carbonations, a benzene solution of poly(styryl)lithium was freeze-dried on the vacuum line followed by introduction of high-purity, gaseous carbon dioxide (Air Products, 99.99% pure). Analysis and characterization of polymeric amines (11) and carboxylic acids (8) were performed as described previously. Benzoyl derivatives of the aminated polystyrenes were prepared in toluene/pyridine (2/1. v/v) mixtures with benzoyl chloride (Aldrich, 99%). 

Particle size is one of the most important characterization parameters for sohd hpid nanoparticle dispersions, and parameters relahng to particle size are consequently reported in all stndies on these systems. Particle size determinations are predominantly performed to conhrm that the desired colloidal size range has been obtained dnring preparation and that it is retained upon storage or further processing (e.g., during freeze drying or sterilization). 

In a more recent study, Webster et al. (2006) report the expression and characterization of lettuce-derived measles vaccine. The MV-H protein expressed in lettuce was demonstrated to be immunogenic in mice following intraperitoneal injection in the absence of adjuvant in addition to intranasal inoculation in the presence of a mucosal adjuvant. The highest response was observed in mice primed first with MV-H DNA and then boosted with an oral formulation of freeze-dried MV-H lettuce in conjunction with a mucosal adjuvant. In addition to this, the type of immune response was found to depend largely on the manner in which MV-H is presented to the immune system. Secreted and soluble forms of MV-H were demonstrated to induce a Th2 type response, while membrane-bound MV-H protein was found to be associated with a Thl response. 

Pharmaceutical Excipients Characterization by IR, Raman, and NMR Spectroscopy, David E. Bugay and 14/ Paul Findlay Polymorphism in Pharmaceutical Solids, edited by Harry G. Brittain Freeze-Drying/Lyophilization of Pharmaceutical and Biological Products, edited by Louis Rey and Joan C. May... 

Nail, S. L., Schwegmani, J. J., Kamp, V. analytical tools for characterization of frozen systems in the development of freeze-dried pharmaceuticals. Amer Pharm... 

In addition to characterizing frozen systems intended to be freeze dried, it is important to characterize the freeze-dried product. This includes determination of the physical state of the dried product that is, crystalline, partially crystalline, or amorphous. It may also include identification of the polymorph of a crystallizing component which exhibits polymorphism and determination of whether the crystal form observed is affected by changes in formulation and processing conditions. For amorphous systems, the glass transition temperature of the amorphous solid, as well as the extent to which Ts changes with residual moisture, may be a critical attribute of the product with regard to both physical and chemical stability. 

Kimura, Y., Ito, T.,Yoshikawa, H., Tachiwaki, T., Hiraki, A. Growth and characterization of homogeneous yttrium-barium-copper oxide (YBa2Cu307 6) powders prepared by freeze-drying method. Jpn. J. Appl. Pltys., Part 2 29,... 

At the steps before the elaboration of carbon nanotube nanocom-posites, wet-STEM can be used for the characterization of nanotubes dispersed in a liquid (see Figure 3.18), and for polymer latex/ nanotubes mixing (before evaporation or freeze-drying to elaborate polymer/carbon nanotube nanocomposites). 

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