Lyophilization technique

Ikeda, M. Development of a multilayer lyophilization technique for parenteral dosage forms. PDA Asian Symposium, p. 261-266, Tokyo, 1994... 

Generally, results with the Carbowax 6000 technique were comparable to the lyophilization technique with the added advantage of faster processing, making the method applicable to routine clinical use in many diagnostic applications. 

The lyophilization technique is the most common method for preparing radiopharmaceutical kits with a prolonged shelf-Ufe. 

Up to World War II, the lyophilization technique was used only on a laboratory scale. The sudden increase of demands in freeze-dried blood plasma resulted in its application on an industrial scale. In the first post-war years, the freeze-drying method was applied to various antibiotics, and very quickly became a valuable method of preserving medicinal products. 

Chapter 7 Lyophilization Technique for Preparing Radiopharmaceutical Kits... 

JW Snowman. Lyophilization techniques, equipment, and practice. In Downstream Processes Equipment and Techniques. New York Alan R. Liss, 1988, pp. 315-351. 

Lyophilization is a similar technique and is, in fact, evaporation at reduced temperature under vacuum. In some cases, an aqueous sample can be frozen and the vapor pressure of the ice is sufficient to produce a relatively rapid rate of evaporation. It can also be used effectively where the substances of interest have vapor pressures that are sufficiently high at room temperature, to cause substance loss under normal evaporation procedures. As the vapor pressure of a substance is exponentially related to the temperature, a relatively small reduction in temperature can reduce the vapor pressure of the sample components sufficiently to render any loss during evaporation relatively insignificant. This technique is gentler than evaporation and,... 

Several variations of the solvent removal technique were developed (6,7). For the PCPP-SA, 20 80, M = 16,000, microspheres were prepared as follows 1 g polymer was dissolved in 1 ml methylene chloride, drug or dye was suspended in the solution, mixed, dropped into silicon oil containing 1-5% of Span 85, and stirred at a known stirring rate. Stirring was done using an overhead stirrer and a three-blade impeller. After 1 hr, petroleum ether was introduced and stirring was continued for another hour. The microspheres were isolated by filtration, washed with petroleum ether, dried overnight in a lyophilizer, sieved, and stored in a freezer. 

Production strains are stored in a dormant form by ai r of the standard culture preservation techniques. Thus, a spore suspension may be mixed with a sterile, finely divided, inert support and desiccated. Alternatively, spore suspensions in appropriate media can be lyophilized or stored in a hquid culture biostat. 

Exudate collection in trap solutions usually requires subsequent concentration steps (vacuum evaporation, lyophilization) due to the low concentration of exudate compounds. Depending on the composition of the trap solution, the reduction of sample volume can lead to high salt concentrations, which may interfere with subsequent analysis or may even cause irreversible precipitation of certain exudate compounds (e.g., Ca-citrate, Ca-oxalate, proteins). Therefore, if possible, removal of interfering salts by use of ion exchange resins prior to sample concentration is recommended. Alternatively, solid-phase extraction techniques may be employed for enrichment of exudate compounds from the diluted trap solution (11,22). High-molecular-weight compounds may be concentrated by precipitation with organic solvents [methanol, ethanol, acetone 80% (v/v) for polysaccharides and proteins] or acidification [trichloroacetic acid 10% (w/v), per-... 

The degradation of proteins in the solid state occur to a lesser extent and typically via different mechanisms than those that occur in solution [109,110]. Lyophilization is currently the more common technique in the manufacture of dried therapeutic proteins however, there is increasing interest in the use of spraydrying, owing to the unique physical nature of the spray-dried powder and its potential usefulness in protein drug delivery. 

In order to preserve, as much as possible, the phenolic content in fruit and vegetable samples, the literature proposed the application of cold temperatures, even reaching to freezing, when lyophilization is the objective. These procedures also could inactivate the enzymes. The freeze-drying is largely the main preservation technique used in the studies related to the identification and quantification of the phenolic compounds of fruit... 

Schellenz, G., Engel, J. Rupprecht, H. Sublimation during lyophilization detected by temperature profile and X-ray technique. International Journal of Pharmaceutics 113, p. 133— 140, 1995. Copyright 1995 Elsevier Science B. V. 

The popularity of this extraction method ebbs and flows as the years go by. SFE is typically used to extract nonpolar to moderately polar analytes from solid samples, especially in the environmental, food safety, and polymer sciences. The sample is placed in a special vessel and a supercritical gas such as CO2 is passed through the sample. The extracted analyte is then collected in solvent or on a sorbent. The advantages of this technique include better diffusivity and low viscosity of supercritical fluids, which allow more selective extractions. One recent application of SFE is the extraction of pesticide residues from honey [27]. In this research, liquid-liquid extraction with hexane/acetone was termed the conventional method. Honey was lyophilized and then mixed with acetone and acetonitrile in the SFE cell. Parameters such as temperature, pressure, and extraction time were optimized. The researchers found that SFE resulted in better precision (less than 6% RSD), less solvent consumption, less sample handling, and a faster extraction than the liquid-liquid method [27]. 

A novel pigment has been isolated from the petals of Rosa hybrida with complex chromatographic techniques and the structure was elucidated with spectroscopic methods and high resolution fast-atom bombardement mass spectrometry, lH NMR, and FTIR. Anthocyanins were extracted from 7.9 kg of petals of Rosa hybrida cv. M me Violet with 80 per cent aqueous ACN containing 0.1 per cent TFA. The extract was purified in a Sephadex LH-20 column, and the fraction eluted with 80 per cent ACN was further fractionated in a HP-20 column using water, 15, 20 and 30 per cent ACN as mobile phases. The last fraction was lyophilized and separated by preparative RP-HPLC using an ODS column (50 X 5 cm i.d.). Solvents were 0.5 per cent aqueous TFA (A) and water-methanol... 

A second motivation to include CE methods is the excellent performance of chiral CE, which is often the first choice technique to separate stereoisomers. Such method can be used complementarily to avoid potential co-elution of isomers or related products, e.g., degradation products, with similar chromatographic properties. Practically, one can fractionally collect the peak volume, lyophilize it, and dissolve the resulting mass in an appropriate solvent. The pre-concentrated sample can then easily be analyzed with a selective and efficient CE method. Another option is to develop an on-line coupling between HPEC and CE to facilitate the analysis. " ... 

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