Heating protocols stability

The stabilized temperature platform furnace (STPF) concept was first devised by Slavin et al. It is a collection of recommendations to be followed to enable determinations to be as free from interferences as possible. These recommendations include (i) isothermal operation (ii) the use of a matrix modifier (iii) an integrated absorbance signal rather than peak height measurements (iv) a rapid heating rate during atomization (v) fast electronic circuits to follow the transient signal and (vi) the use of a powerful background correction system such as the Zeeman effect. Most or all of these recommendations are incorporated into virtually all analytical protocols nowadays and this, in conjunction with the transversely heated tubes, has decreased the interference effects observed considerably. 

Stress testing is used to help identify degradation pathways under the influence of accelerated heat, light, and RH conditions in the presence or absence of air or oxygen. Such stability testing protocols represent an important aspect of a pharmaceutical ingredient process validation program. 

Internal mixers must be ran in a full or nearly full condition, so a batch recipe is calculated to provide an appropriate volume. If not filled, the ingredients will not be properly sheared and heat transfer will be compromised. Typical commercial mixers have a batch size of at least 100 pounds of compound. A mixer of this size will have a drive motor of no less than 75 horsepower. Proper dispersive mixing is a balance between proper shear, sequence of addition of ingredients, and thermal stability. Mixers have extensive monitoring instrumentation that provides continuous feedback about thermal conditions, rotor torque, and rotor speed. Once a mixing process has been developed, a standard protocol is followed for preparation of the compound. 

Information on the stability of the finished product is collected in the proposed container/closure system to support the phase II clinical studies. At this stage of development, protocol-driven stability studies are initiated and the conditions indicated in the ICH guideline are recommended. The test frequency is every 3 months in the 1st year and every 6 months in the 2nd year. The storage conditions recommended in the ICH guideline such as room temperature (25°C/60% RH), light (1.2 million lux hours), and heat/humidity... 

The following protocols (6-10) describe the synthesis of some cholesterol-based acrylates and their photopolymerization in an aligned cholesteric phase. The protocols utilize a modification of a system previously described by Shannon. 5 6 ip ie absence of a diacrylate comonomer, the cholesteric phase produced initially on copolymerization is not stable and reverts to a smectic phase on a single cycle of heating and cooling. In the presence of the diacrylate the first-formed phase is stable. This is one example of how crosslinking can stabilise the liquid crystal phase in liquid crystalline elastomers, others include, the so-called, polymer-stabilized liquid crystals and those described in the later protocols. 

The most important testing protocol for resistance to deterioration of critical physical properties upon exposure to heat, especially over prolonged periods of time, was designed by the Underwriters Laboratories (UL) [1], The UL temperature index is used to qualify materials for applications (such as use in electrical equipment) regulated by UL. The main purpose of these tests is to ensure that a polymer can be used safely for a prolonged period of time in these applications. A larger value of the UL temperature index implies greater stability, defined in... 

Table I. Thennal stability comparisons of a variety of NLO chromophores using thermal protocol techniques, (a) Temperature for which 10% of the original chromophore nonlinearity is lost after 0.5h heating, (b) Temperature where 10% of the original molar extinction coefficient at the long wavelength max is lost after 0.5h. (c) Temperature where 10% of the measured heat of the exothermic DSC decomposition is lost after 0.5h. (d) Temperature where 10% of the original absorbance at the max is lost upon heating for 0.5h for chromophores tethered to a polyimide backbone.

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