Freeze-drying temperature

Representative emissivity data at freeze-drying temperatures are given in Table 5 for some materials of relevance to freeze-drying problems. Emissivities... 

The freeze drying of antibiotics and blood serum have largely represented the beginning of industrial lyophilization. Neumann [3.34] wrote in 1952 The (freeze drying) temperature for the older, not well purified Penicillin preparations had to be kept surprisingly low. It could not exceed -25 °C or -40 °C and later on Today Peniciilin is manufactured as crystals without the need of freeze drying . 

Drying to remove solvent from a gel drying method (e.g. evaporative vs. supercritical vs. freeze drying) temperature and heating rate pressure and pressurization rate time... 

The temperature necessary for freeze-drying temperature at which the product is stable during freeze-drying, temperature at which melting starts and at which the structure is destroyed completely (Figure 17). 

In Table 45.5, initial freezing temperatures and percentage of frozen moisture as a funetion of temperature of several materials are presented. It follows that in most substances the freeze-drying temperature should be lower than -40°C beeause at this temperature a signifieant part of moisture remains unfrozen. 

Tq- inlet (ambient) temperature - freeze-drying temperature Tf - regeneration temperature T, - freezing temperature... 

Schnell, U., Jensen, P. (2007). Determination of maximum freeze drying temperature for PEG-impregnated archaeolt cal wood. Studies in Conservation, 52(1), 50-58. 

Sublimation of ice crystals to water vapor under a very high vacuum, about 67 Pa (0.5 mm Hg) or lower, removes the majority of the moisture from the granulated frozen extract particles. Heat input is controlled to assure a maximum product end point temperature below 49°C. Freeze drying takes significantly longer than spray drying and requires a greater capital investment. 

Freeze drying, or lyophilization, is normally reserved for temperature-sensitive materials such as vaccines, enzymes, microorganisms, and therapeutic proteins, as it can account for a significant portion of... 

Freeze-drying, like all drying processes, is a method to separate liquid water from a wet solid product or from a solution or dispersion of given concentration. However, the main difference is that the liquid water is separated by solidification (i.e., the formation of ice crystals) and subsequent vacuum sublimation instead of evaporation. This allows a drying at subzero temperatures which can be advantageous in case of heat-sensitive products. There are two general applications... 

Finally,Captopril is produced. Thethioester (0.85g) isdissolved in5.5N methanolicammonia and the solution is kept at room temperature for 2 hours. The solvent is removed in vacuo and the residue Is dissolved in water, applied to an ion exchange column on the H cycle (Dowex 50, analytical grade) and eluted with water. The fractions that give positive thiol reaction are pooled and freeze dried. The residue Is crystallized from ethyl acetate-hexane, yield 0.3 g. The 1 -(3-mercapto-2-D-methylpropanoyl)-L-proline has a melting point of 103°C to 104°C. 

Bj Pivaloyloxymethyl D(—)-Ot-aminobenzylpenicillinate. hydrochloride To a solution of pivaloyloxymethyl D(—)-a-azidobenzylpenicillinate (prepared as described above) in ethyl acetate (75 ml) a 0.2 M phosphate buffer (pH 2.2) (75 ml) and 10% palladium on carbon catalyst (4 g) were added, and the mixture was shaken in a hydrogen atmosphere for 2 hours at room temperature. The catalyst was filtered off, washed with ethyl acetate (25 ml) and phosphate buffer (25 ml), and the phases of the filtrate were separated. The aqueous phase was washed with ether, neutralized (pH 6.5 to 7.0) with aqueoussodium bicarbonate, and extracted with ethyl acetate (2 X 75 ml). To the combined extracts, water (75 ml) was added, and the pH adjusted to 25 with 1 N hydrochloric acid. The aqueous layer was separated, the organic phase extracted with water (25 ml), and the combined extracts were washed with ether, and freeze-dried. The desired compound was obtained as a colorless, amorphous powder. 

Freeze-dried aequorin is also quite stable, but the process of drying always causes a loss of luminescence activity (see the last part of Section 4.1.2). All forms of aequorin are satisfactorily stable for many years at — 50°C or below, but all rapidly deteriorate at temperatures above 30-35° C. A solution of aequorin should be stored frozen whenever possible because repeated freeze-thaw cycles cause little harm to aequorin activity. 

Aqueous solutions of some drugs are so unstable that chemical stabilization is impossible. In this case the dmg itself, not its aqueous solution, is sterilized by dry heat (160°C for 2 hours or its equivalent at higher temperatures) in its final container and dissolved immediately before use by the addition of sterile water (Water for Injechons BP). For dmgs which are both thermolabile and unstable in aqueous solution, a sterile soluhon of the dmg is freeze-dried in the final container and is reconstimted as above just before use (e.g. many anhbiotics, Hyaluronidase BP). 

---