Freeze-drying Procedure

A product should be closed as soon as practicable after filling. The only major exception to this is the freeze drying procedure, whereby the container is filled with liquid, partially closed, and freeze dried. Then the closure operation is completed. 

Freezing steps are common to both freeze-thawing and freeze-drying procedures, and will affect viability of the cells. 

In parallel, the dry latexes, obtained by the freeze drying procedure, and coated latexes were analyzed by solid-state Si NMR in order to determine the extent of condensation of silanols... 

In this work, we have analyzed the phase behavior of various freeze-dried mixtures of DPPE, DPPC, and cholesterol and have examined the effects of trehalose addition to these liposomes. Generally, dehydration leads to increase in transition temperature of the phospholipids and also to phase separation. Addition of trehalose, however, can prevent the increase in transition temperature and phase separation freeze-dried DPPC-cholesterol liposomes exhibit only one transition and their retention capability increases by more than 40%. Further studies on the phase separation and stability of multicomponent model membranes will be required to understand better its relation to the survival of cells to freeze-drying procedures. 

H Willemer. Experimental freeze-drying procedures and equipment. In L Rey and JC May, ed. Freeze-drying/Lyophilization of Pharmaceutical and Biological Products. New York Marcel Dekker, 1999. 

Proteinaceous active substances are usually formulated in an elaborated excipient system prior to the freeze-drying procedure. Bulking agents, such as mannitol or glycine, are used to increase the bulk volume and provide a suitable matrix in which a small quantity of protein is dispersed [27], Further details regarding use of cryoprotective excipients are described in Sect. 22.2.5. 

If the sample is of a liquid form under standard temperatnre and pressure conditions, they must be converted into a solid form that will be vacuum stable. This is generally accomplished through freeze-drying procedures covered in Section 5.2.3. 

PVA-AgX membranes exhibited large selectivities and benzene permeation rates for the separation of benzene and cyclohexane over a wide range of feed concentrations. Much lower selectivites were observed for styrene/ethylbenzene and o-xylene/p-xylene separations. Long term transport depends on the membranes remaining hydrated. A freeze-drying procedure was developed that provided homogeneous distribution of silver in the PVA membranes. Absorption/extraction experiments indicated that the membranes had low absorption and diffusion selectivities for benzene/cyclohexane. 

To remove the pore solution in hydrating cement and to stop the reaction, either solvent exchange (focusing on the determination of bound water and identification of hydrates such as ettringite) or a freeze-drying procedure (for the minimisation of carbonation to determine portlandite content or for the characterisation of C-S-H) is recommended. 

---