Choice of technique

Many different electrochemical and non-electrochemical techniques exist for the study of corrosion and many factors should be considered when selecting a technique. Corrosion rate can be determined by Tafel extrapolation from a potentiodynamic polarization curve. Corrosion rate can also be determined using the Stem-Geary equation from the polarization resistance derived from a linear polarization or an electrochemical impedance spectroscopy (EIS) experiment. Techniques have recently been developed to use electrochemical noise for the determination ofcorrosion rate. Suscephbility to localized corrosion is often assessed by the determination of a breakdown potenhal. Other techniques exist for the determinahon of localized corrosion propagahon rates. The various electrochemical techniques will be addressed in the next section, followed by a discussion of some nonelectrochemical techniques. 

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These techniques have been described previously in the pressure measurement section. Usually, one of the flow-measuring devices and the required instrumentation is incorporated as a part of the plant piping. The choice of technique depends on the allowable pressure drop, flow type, accuracy required, and cost. 

Therefore, you should develop a complete computer specification sheet for each of the predictive maintenance systems that will be used. A comparison of the list will provide a compatible computer configuration that will support each of the techniques. If this is not possible, you may have to reconsider your choice of techniques. 

Natural products and common industrial chemicals in massive form are seldom useful as catalysts because they have low specific surface areas, may contain various amounts of impurities that have deleterious effects on catalyst performance, do not usually have the exact chemical composition desired, or are too expensive to use in bulk form. The preparation of an industrial catalyst generally involves a series of operations designed to overcome such problems. Many catalysts can be produced by several routes. The actual choice of technique for the manufacture of a given catalyst is based on ease of preparation, homogeneity of the final catalyst, stability of the catalyst, reproducibility... 

Studies on the dynamics of complexation for guests with cyclodextrins have been carried out using ultrasonic relaxation,40 151 168 temperature jump experiments,57 169 183 stopped-flow,170,178,184 197 flash photolysis,57 198 202 NMR,203 205 fluorescence correlation spectroscopy,65 phosphorescence measurements,56,206 and fluorescence methods.45,207 In contrast to the studies with DNA described above, there are only a few examples in which different techniques were employed to study the binding dynamics of the same guest with CDs. This probably reflects that the choice of technique was based on the properties of the guests. The examples below are grouped either by a type of guest or under the description of a technique. 

How do chemists collect the data they need to determine a reaction rate To determine empirically the rate of a chemical reaction, chemists must monitor the concentration or amount of at least one reactant or product. There are a variety of techniques available. The choice of technique depends on the reaction under study and the equipment available. 

When contemplating the choice of technique one must keep in mind two further, highly relevant. Laws of Experimentation ... 

It is probably best to regard electrothermal and flame atomization and plasma-based instruments as complementary techniques. Some factors which govern the choice of technique for a given application are given below. 

A representative selection of applications is shown in Table 6, which illustrates the wide choice of techniques that have been used, with attention being paid to the type of sugar and matrix, eluent, and stationary phase, as well as the appropriate detection method. An example of a... 

The choice of techniques for a specific problem depends not only on the nature of the material in question but also on the types of answer required. Methods for the determination of metal speciation range from very simple separations based on bulk physical properties to detailed structural analyses, which can measure interatomic distances and orientations. The complete chemical identification of a total unknown is a different problem from one in which a distinction must be made between, perhaps as few as two, possibilities. The foregoing chapter concentrates on techniques for chemical identification, which, together with the separation techniques which are discussed in depth elsewhere, make the determination of metal speciation possible. 

In EMEP, ICP-MS is dehned as the reference technique. The exception is mercury, where cold vapor atomic fluorescence spectroscopy (CV-AFS) is chosen. Other techniques may be used, if they are shown to yield results of a quality equivalent to that obtainable with the recommended method. These other methods include graphite furnace atomic absorption spectroscopy (GF-AAS), flame-atomic absorption spectroscopy (F-AAS), and CV-AFS. The choice of technique depends on the detection limits desired. ICP-MS has the lowest detection limit for most elements and is therefore suitable for remote areas. The techniques described in this manual are presented with minimum detection limits. Table 17.2 lists the detection limits for the different methods. 

The four most common approaches to quantitative HSGC calibration are classical external standard, internal standard, standard addition, and multiple headspace extraction (MHE). The choice of technique depends on the type of sample being analyzed. 

In summary, today a multiplicity of different types of plastic is required to be printed, many in compositions with a number of different additives and often in rather complex presentations (such as co-extrusions and laminates). This means in turn that there is need for a variety of approaches to the problems of printing at the speeds required and to obtain satisfactory results—not only in terms of the choice of technique but also the design of machinery capable of handling the pieces of work and of formulations of inks with the correct qualities of adhesion, drying, and colour. 

The wide range of molecular techniques available and the rapid pace of new developments make it difficult for an individual to stay apprised of all aspects of the field that might impinge on the research at hand. For this reason, other researchers involved in molecular genetics are a key element of the local environment. This may include other members of the same research group, scientists who share the laboratory facility, or others doing various kinds of molecular genetics research at the same or nearby institutions. The collective molecular expertise in the local environment (and how well one can hope to make use of it) should be carefully assessed, and it may influence decisions on the choice of technique and the scope of research envisioned. 

This guide is intended for the experts who participate in the elaboration of European Pharmacopeia monographs it establishes the general rules to be followed. This document specifies the philosophy behind the choice of techniques for identification testing of a substance and for the determination of the limit contents of impurities and the methods used to detect them. 

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