Storage stability, glass temperature

Figure 5 Effect of excipients on the storage stability of freeze-dried human growth hormone (hGH). Samples were stored for I month at 40°C. Solid bars, aggregation (primarily dimer). Hatched bars, chemical degradation via methionine oxidation and asparagine deamidation. The glass transition temperatures of the initial freeze-dried formulations are given above the bars when a gla.ss transition temperature could be measured by DSC. The glycine mannitol formulation is a weight ratio of hGH glycine mannitol of 1 1 5, the dex-tran formulation is 1 6 hGH dextran 40, none means no stabilizer, and the others are 1 1 hGH stabilizer. All formulations contain sodium phosphate buffer (pH 7.4) at 15% of the hGH content. Initial moisture contents are all ==1%. (Data from [4].)...

A number of systems show marked deterioration of stability as temperature exceeds the glass transition temperature, but for storage well below the glass transition temperature, stability does not appear to depend directly on the difference between and the storage temperature [4]. The correlation between reactivity and 7g is most easily discussed in terms of the WLF equation. The WLF equation [4,53] is an expression for relaxation time, roughly equivalent to the VTF equation, that may be derived using free volume concepts. With fixed constants, the WLF equation states that the ratio of relaxation time at any temperature to the... 

The stability of the fish oils was tested at -18°C, +20 C and +37°C over a period of 14 months. There was no significant difference associated with stability in the concentrations of CBs or the total lipid content in either fish oil stored at the three temperatures. This stability was expected as it is well known that CBs are very stable. The matrix stability was assured by the measures taken such as use of dark glass ampoules and sealing under argon. Storage at a temperature at ca. +20°C is acceptable for long-term stability a higher temperature up to +37°C is unlikely to cause any measurable effect on the CB-content. 

It is also essential to consider the glass transition temperature of the freeze-dried product, particularly with a view to predicting physical and chemical storage stability. The relationship between the physical stability of freeze-dried formulations and Tg must be considered not only in terms of recrystallization but also of product collapse. For example, te Booy et al. (119) showed that storage of sucrose-containing freeze-dried formulations above Tg may result in product shrinkage, collapse, or excipient recrystallization. 

Implication of Glass Temperature on Storage Stability of Encapsulated Flavors... 

High temperature stability of the fuels was measured using an Alcor, Inc. Jet Fuel Thermal Oxidation Tester (JFTOT) (j ). Low temperature (storage) stability was determined by measurement of gums, contamination and peroxide concentration (all by ASTM standard methods) before and after exposure to temperatures of 60 C for four weeks. The fuels were stored in l low actinic, dark pyrex glass bottles and were loosely covered to prevent exposure to airborne particulates. Air could still diffuse into the vessel. The vessels with fuel and various additives were thermostated at 60 C for the specified length of time. 

Glass Transition Temperature as a Measure of Storage Stability... 

---