Essential method characteristics

Table 2. Some essential method characteristics of the two calibration series. ...

Even if most examples and procedures presented apply to in-house validation, the procedure does not distinguish between validations conducted in a single laboratory and those carried out within inter-laboratory method performance studies. A preference for inter-laboratory studies can be concluded from the statement that laboratories should always give priority to methods which have been tested in method performance studies. Within the procedure a profound overview of different categories of analytical methods according to the available documentation and previous external validation is given. For example, if a method is externally validated in a method performance study, it should be tested for trueness and precision only. On the other hand, a full validation is recommended for those methods which are published in the scientific literature without complete presentation of essential performance characteristics (Table 9). 

Before the ruggedness test could be contemplated it was essential to fully validate the method with respect to other method characteristics. Hence the following tests were carried out, specificity, spectral purity of chromatographic peaks, linearity of detector response, and repeatability over 100 injections. Satisfactory results were achieved for all these experiments before we continued to the ruggedness test. 

Since uracil and thymine, like cytosine, are fundamental nucleic acid bases, they have been treated by many methods of quantum chemistry in view to establish the essential electronic characteristics of their ground states. 

It is surprising to observe to what a large extent the compounds of this series are frequently depicted in arbitrary and erroneous forms in otherwise excellent papers and textbooks—the more so as the utilization of the appropriate tautomeric forms is, as will be seen in Section II, of fundamental importance for the appropriate presentation and understanding of biological structures and phenomena in which these compounds play a decisive role. During recent years much work has been carried out, both experimentally by a wide variety of techniques and theoretically with the help of the refined methods of quantum chemistry, in order to ascertain the relative importance of the different tautomeric forms and to determine their essential electronic characteristics. The present chapter is devoted to a summary of this work. 

Individual scratch is often done with a constant loading rate (which includes constant load) and constant scratch rate. The scale of damage of interest varies from macroscopic features to those of nanometer scale. This renders comparisons between studies difficult. The recent concerted industry-university effort (6,7,44) has led to the development of a scratch test method and universal scratch testing equipment to facilitate good scratch test practices and fimdamental study of scratch behavior of polymers. Figure 4 presents the scratch tester that was developed. It aims to provide reasonable capability to vary experimental conditions for capturing the essential scratch characteristic of the materials with reliable and reproducible results. One unique feature of the tester is its ability to alter scratch load and velocity at a linear rate. This feature is foimd to be useful in understanding scratch behavior of polymers, to be presented in later sections. 

The diversification of synthesis methods and of monomers implied in obtaining oligoesteracrylates created compounds with complex structures not representable by the general formula (1). For this reason, membership of some oligomers in a class of oligoacrylates is classified using the following essential structure characteristics ... 

In this chapter, we will consider the most popular photocatalyst systems other than Ti02. Their synthesis methods, characteristics, optimisations, and design will be presented. Last but not least, the design and synthesis of promoters, which play a very essential role in photocatalyst systems, will also be demonstrated at the end of this chapter. 

The existence of this situation (for nonporous solids) explains why the ratio test discussed above and exemplified by the data in Table XVII-3 works so well. Essentially, any isotherm fitting data in the multilayer region must contain a parameter that will be found to be proportional to surface area. In fact, this observation explains the success of Ae point B method (as in Fig. XVII-7) and other single-point methods, since for any P/P value in the characteristic isotherm region, the measured n is related to the surface area of the solid by a proportionality constant that is independent of the nature of the solid. 

Processes that are essentially modifications of laboratory methods and that allow operation on a larger scale are used for commercial preparation of vinyhdene chloride polymers. The intended use dictates the polymer characteristics and, to some extent, the method of manufacture. Emulsion polymerization and suspension polymerization are the preferred industrial processes. Either process is carried out in a closed, stirred reactor, which should be glass-lined and jacketed for heating and cooling. The reactor must be purged of oxygen, and the water and monomer must be free of metallic impurities to prevent an adverse effect on the thermal stabiUty of the polymer. 

If the secondary ion component is indeed negligible, the measured SNMS ion currents will depend only on the ionizing mode, on the atomic properties of the sputtered atoms, and on the composition of the sputtered sample. Matrix characteristics will have no effect on the relative ion currents. SNMS analysis also provides essentially complete coverage, with almost all elements measured with equal facility. All elements in a chemically complex sample or thin-film structure will be measured, with no incompleteness due to insensitivity to an important constituent element. Properly implemented SNMS promises to be a near-universal analytical method for solids analysis. 

Industrial carbon anodes and artificial graphites are not a single material but are rather members of a broad family of essentially pure carbon. Fortunately, artificial graphites can be tailored to vary widely in their strength, density, conductivity, pore structure, and crystalline development. These attributes contribute to their widespread applicability. Specific characteristics are imparted to the fmished product by conti ollmg the selection of precursor materials and the method of processing [19]... 

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