Analytical methods stress

Aben, H., Idnurm, S., Josepson, J., Kell, K.-J., Puro, A. Optical tomography of the stress tensor field. Proc. SPIE, ISfS "Analytical methods for optical tomography , 1991, 220-229. 

Stress in the Centrifuge Rotor The stress in the centiifuge rotor is quite complex. Analytical methods, such as the finite element... 

Generally the material response stress versus particle velocity curves in Fig. 8.6 are nonlinear and either a graphical or more complicated analytic method is needed to extract a spall strength, Oj, from the velocity or stress profile. When behavior is nominally linear in the region of interest a characteristic impedance (Z for the window and for the sample) specify material... 

ISO 7933 EN ii515i Thermal stress evaluation in hot cnviron-iTicnts. Analytical method Elor environments Analytical determination and interpretation of thermal stress ussny oalculatio.n of required sweat... 

It has already been stressed that the discovery of superoxide as the enzymatically produced diffusion-free dioxygen radical anion [1-3] was a pivotal event in the study of free radical processes in biology. It is not of course that the McCord and Fridovich works were the first ones in free radical biology, but the previous works were more of hypothetical character, and only after the identification of superoxide by physicochemical, spectral, and biochemical analytical methods the enzymatic superoxide production became a proven fact. 

The guidelines stress, however, that internal quality control is not foolproof even when properly executed. Obviously it is subject to errors of both kinds , i.e. runs that are in control will occasionally be rejected and runs that are out of control occasionally accepted. Of more importance, IQC cannot usually identify sporadic gross errors or short-term disturbances in the analytical system that affect the results for individual test materials. Moreover, inferences based on IQC results are applicable only to test materials that fall within the scope of the analytical method validation. Despite these limitations, which professional experience and diligence can alleviate to a degree, internal quality control is the principal recourse available for ensuring that only data of appropriate quality are released from a laboratory. When properly executed it is very successful. 

Oxidative ozonolysis, analytical methods, 737 Oxidative stress... 

The selectivity of an analytical method is determined by comparing test results from the analysis of samples containing impurities (related compound), degradation products (originated from samples submitted to stress conditions), or placebo ingredients with those obtained from the analysis of samples without impurities, degradation product, or placebo ingredients. 

The stress studies should demonstrate that impurities and degradants from the active ingredient do not interfere with the quantitation of the API [12]. Stress testing of the API, in addition to validating the stability-indicating power of the analytical method, can also help establish the degradation pathways and the intrinsic stability of the molecule [7]. 

If foam is held in a compressed state for a time, it does not return to its original thickness. This effect is referred to as compression set and could be important because the foams we will be designing will be under more or less constant compressive stresses in normal service. The analytical method involves a certain amount of compression of the foam. It is held in the compressed state for 22 hours at 7()C, then allowed to relax for 30 minutes. The thickness is measured and compared to the original thickness. See Figure 3.4. 

Modem analytical methods for RDX tend to stress instrumental techniques such as mass spectrometry, chromatography and polarography... 

Stress testing is the main tool that is used to predict stability problems, develop analytical methods, and identify degradation products and pathways. Since there are no detailed regulatory guidelines that describe how to carry out stress testing studies (nor has there ever been a textbook or reference book devoted to the subject), stress testing has evolved into an artful science that is highly dependent on the experience of the company... 

Examining degradation products [under stress conditions] is useful in [establishing degradation pathways] and developing and validating suitable analytical methods. 

The first task before beginning stress-testing studies is to gather all the relevant information about the compound. Information such as molecular structure, solubility, pA (s), known chemical instability, hygroscopicity, enantiomeric purity, etc. is important. In addition, previously established analytical methods may provide a starting point for development of more discriminating methods required for the separation of the complex mixtures which may result from stress degradation. 

Most of the following discussion on method development assumes that one is trying to develop an analytical method for a specific compound. Another viable approach, however, is to develop generic analytical methods that can be used for the analysis of stress-testing samples from multiple compounds. A short discussion of the development of generic methods is provided later in the section. 

LY334370 hydrochloride will be used as an example to illustrate the stresstesting method development process. Ten stressed samples of LY334370 hydrochloride were prepared as described in Table 8 and used to develop the stress-testing analytical method. 

Stress testing is an important part of the drug development process as it provides knowledge about the degradation chemistry of drug compounds. This knowledge is used primarily to develop stability-indicating analytical methods but is also useful for other purposes such as formulation develop-... 

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