Freeze-dryers

Surface temperatures may range from below freezing in the case of freeze dryers to above 800 K in the case of indirect dryers heated by combustion products. 

Purification of luciferin (Rudie etal., 1976). The luciferin fractions from the DEAE-cellulose chromatography of luciferase were combined and concentrated in a freeze-dryer. The concentrated solution was saturated with ammonium sulfate, and extracted with methyl acetate. The methyl acetate layer was dried with anhydrous sodium sulfate, concentrated to a small volume, then applied on a column of silica gel (2 x 18 cm). The luciferin adsorbed on the column was eluted with methyl acetate. Peak fractions of luciferin were combined, flash evaporated, and the residue was extracted with methanol. The methanol extract was concentrated (1 ml), then chromatographed on a column of SephadexLH-20 (2 x 80 cm) usingmethanol asthe solvent. The luciferin fractions eluted were combined and flash evaporated. The residue was... 

They may also be required in industrial applications where they become part of venting systems on fermenters, centrifuges, autoclaves and freeze-dryers. Certain types of filter (membrane filters) also have an important role in sterility testing, where they can be employed to trap and concentrate contaminating organisms from solutions under... 

In freeze-drying, a solution is filled into vials, a special slotted stopper is partially inserted into the neck of the vial (Fig. 3), and trays of filled vials are transferred to the freeze-dryer. The solution is frozen by circulation of a fluid, such as silicone oil, at a temperature in the range of — 35 to about — 45°C through internal channels in the shelf assembly. When the product has solidified sufficiently, the pressure in the freeze-dry chamber is reduced to a pressure less that the vapor pressure of ice at the temperature of the product, and heat is applied to the... 

Barriers to heat transfer produce corresponding temperature differences in a freeze-drying system, the actual temperature profile depending upon the rate of sublimation, the chamber pressure, and the container system as well as the characteristics of the freeze dryer employed. An experimental temperature profile is shown in Figure 5 for a system where vials were placed in an aluminum tray with a flat 5 mm thick bottom and a tray lid containing open channels for escape of water vapor. Here, heat transfer is determined by four barriers ... 

A heat transfer coefficient is defined as the ratio of the area-normalized heat flow to the temperature difference between the heat source (the shelf) and the heat sink (the frozen product). For the case of vials resting directly on the freeze dryer shelf, the vial heat transfer coefficient, Kv, is defined by... 

The chamber-to-condenser pathway usually involves dimensions on the order of 10 cm or greater even for laboratory freeze dryers. Here, the ratio of radius to mean free path is on the order of 0.01 or less, and flow should be essentially viscous flow. Conductance should be linear in pressure, with a zero pressure intercept near zero. Qualitative agreement with theory is observed (data not shown). 

Two special cases of radiative heat transfer which are applicable to heat transfer in freeze drying are illustrated by Figure 32. Heat transfer between body 1 and body 2 are illustrated for case I (Fig. 32a), where body 1 is of much greater area than body 2, Ai A2, and surrounds body 2. The freeze-drying example is heat exchange between the top of the vial (body 2) and the freeze dryer shelf... 

The heat transfer data discussed above refer only to the average behavior of a vial of a given type which is surrounded by other vials in a hexagonal packing array of vials. We now consider intervial variations in heat transfer in a set of nominally equivalent vials and variations in heat transfer arising from variations in the position of the vial in the array. An experiment demonstrating such variations is described by Figure 35. Each circle represents a vial placed on a temperature-controlled shelf in a small laboratory freeze dryer. The vials contained pure... 

A freeze dryer (lyophilizer) was employed for vacuum drying (23°C at -0.05... 

Fig. 2.60. Photograph of a vibration dryer with 10 m2 surface vibrated with a frequency of 50 Hz. Top Freeze dryer with the product feeding system in front. Bottom Heated vibration shelves removed from the chamber (slides 21 and 22 from [2.29]).

Haseley, P. New cooling and sterilization technology in freeze-dryers and a comparisation of operating costs. PDA Aisan Symposium, p. 305-317, Tokyo 1994... 

Steiner, R. VHP -Sterilisation of freeze-dryers. ISPE-Seminar Lyophilisation, Antwerp, Nov. 1994. Internnational Society of Pharmaceutical Engineering (ISPE). 

Sterilization of freeze-dryers. Technical Monograph No. 5. The Parenteral Society, 6 Frankton Gardens, Stratton St. Magaret, Swindon, Wiltshire, 1994... 

Gaster, A. J. In place cleaning systems for freeze dryers. PDA Asian Symposium, p. 289-293, Tokyo, 1994... 

Willemer, H. Data to be considered for freeze dryers to be used in freeze drying of transplants (especially bones). 1th European congress of tissue banking and clinical application. Berlin, Oct. 1991... 

Monger, P. Freeze Dryer Validation, p. 157. Good Pharmaceutical Freeze-Drying Practice, Editor Cameron. P., Interpharm Press, Inc., Buffalo Grove, If, USA 1997... 

Freeze-desalination, 26 71 Freeze dryers, 9 135-136 Freeze drying, 9 93, 116 11 543 ceramics processing, 5 656g coffee, 7 262... 

Gieseler et al. utilized tunable diode laser absorption spectroscopy to detect water vapor concentrations, gas velocities and mass flow during freeze-drying of pure water at different pressure and shelf temperature settings and of a 5%w/w mannitol solution. The analyzer was interfaced to the spool that connected the dryer chamber to the condenser. The reported method was advantageous in that primary and secondary drying end-point control based upon mass flow rate was independent of freeze-dryer size and configuration. ... 

A freeze-dryer must be purchased that either has a large built-in chamber, or to which a chamber can be attached. Some smaller ones are mainly for small-scale work when multiple samples are held in glass flasks or ampoules, which are attached to a manifold equipped with isolation valves. 

SOPs detailing step-by-step operational procedures for specific items of equipment (e.g. autoclaves, homogenizers, freeze-dryers, pH meters, product labelling machines, etc.) ... 

Area B Loading freeze dryer LAP (room no. ) Class 100... 

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