Freeze-drying treatment method

After consideration of published chemical results, Grattan and Mathias (26) concluded that for routine conservation of small amounts of waterlogged wood, chemical analysis is unnecessary. They felt that the use of specific gravity to calculate loss of cell wall material was more economical and less time consuming to perform. This conclusion led to the development of the standard freeze-drying treatment method used at the Canadian Conservation Institute. 

The resuspended and formulated Fraction II precipitate normally contains some aggregated IgG and trace substances that can cause hypotensive reactions in patients, such as the enzyme prekail ikrein activator (186). These features restrict this type of product to intramuscular adininistration. Further processing is required if products suitable for intravenous adininistration are required. Processes used for this purpose include treatment at pH 4 with the enzyme pepsin [9001-75-6] being added if necessary (131,184), or further purification by ion-exchange chromatography (44). These and other methods have been fiiUy reviewed (45,185,187,188). Intravenous immunoglobulin products are usually suppHed in the freeze-dried state but a product stable in the solution state is also available (189). 

The reader is referred to basic studies of mass transfer in freeze-drying by Pikal and coworkers for in-depth treatment of the theoretical and practical aspects of mass transfer [29,32], Briefly, the rate-limiting step in mass transfer is transfer of water vapor through the partially dried matrix of solids. Resistance of the dried layer increases in a more or less continuous fashion as the depth of the dried layer increases, and the resistance also increases with the concentration of solids in the dried layer. Other factors can also affect the resistance of the dried layer, such as the method of freezing faster freezing tends to create a higher resistance in the dried layer. 

Pretreatment of biological samples for surfactant analysis is usually straightforward and includes either homogenising with anhydrous sodium sulphate or freeze-drying. Below, the sample treatment methods for extraction and clean-up of non-ionic and anionic surfactants in biota that have been encountered in the literature are reviewed. 

A simple and efficient method to obtain considerably smaller particles with a narrow size distribution from usual precursors was proposed by Ding et al. and Shi et al. Precursors obtained by freeze-drying of coprecipitated hydroxides (or by other chemical synthesis methods) are processed in a planetary mill with excess NaCl. Such a treatment reduces the size of the soft agglomerates formed during precipitation and insulates these aggregates from each other. The formation of complex oxide particles during thermal decomposition of the mixture occurs... 

Plasma-derived therapeutic proteins are parenteral biologies that are purified on an industrial scale. All biologies derived from human sources, such as plasma, carry the risk of viral contamination. Thus, in order to market a medicinal product derived from human plasma, manufacturers must assure the absence of specific viral contamination. Virus validation studies are performed to evaluate the capacity of a manufacturing process to remove viral contaminants. Virus clearance across three different terminal inactivation steps, low pH incubation of immunoglobulins (IgG), pasteurization of albumin, and freeze dry/dry heat treatment of plasma-derived products (Factor VIII and Protein G), is discussed in this article. The data show that, like all other upstream virus reduction steps, the methods used for terminal inactivation are process and product dependent, and that the reduction factors for an individual step may be overestimated or underestimated due to inherent limitations or inadequate designs of viral validation studies. 

Many freeze dried coagulation concentrates are heated to reduce the risk of virus transmission. During terminal dry-heat treatment, freeze dried FVIII concentrate in final container is heated for periods ranging from several minutes to several days at temperatures ranging from 60 to This method was orig-... 

The impact of formulation on virus reduction and product recovery (e.g., potency) was evaluated during terminal freeze dry/dry heat treatment studies with an unlicensed Fraction I derived product, that will be designated Protein G. As shown in Fig. 10, the optimum formulation, that achieved >4 logio PPV inactivation and 80% product recovery, was one that contained 2% albumin, no NaCl, and <0.3%o moisture by the Karl Fischer coulometric method. In contrast, freeze dry/dry heat treatment of product formulated with no albumin, 150mM NaCl and low moisture resulted in approximately 3 logio PPV reduction and 35% product recovery. Thus, minor changes in formulations such as the addition of 2% albumin may impact virus reduction and product recovery during a freeze dry/dry heat treatment. 

Fig. 9 Kinetics of non-enveloped virus inactivation during 80°C heat treatment of freeze dried Factor VIII (FVIII) concentrate (A) in the presence of high cake moisture (>0.8% moisture) or (B) in the presence of low cake moisture (<0.8% moisture). Methods were as described in Fig. 8 (gray boxes = logio virus titer, closed circles = % moisture, and dashed line = virus detection limit).

An interesting method that was developed some years ago combines two processes for waterlogged wood treatment. The first step is freeze-drying in order to obtain dried wood with maximum dimensional stability, and the second step is impregnation of this dried wood by an unsaturated polyester resin. The conservation of a pole used as a ladder excavated from a... 

Processes available for the extraction of natural organics from waters include vacuum distillation, freeze-drying, freeze concentration, co-precipitation, ultrafiltration, reverse osmosis (RO), solvent extraction, sorption, anion exchange, and non-ionic macroporous sorbents (Aiken (1985)). Many of these methods include chemical treatment that may alter the HS characteristics. In this section, the most common methods for the processing of large samples will be described. An important issue in NOM extraction is the recovety of organics. Minimising the loss of certain fractions, such as small compounds which are difficult to treat, is also important. 

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