Choice of a method

Analytical Methods. Most analytical methods use the oxidizing power of iodine for its deterrnination. The results are generaHy expressed as an equivalent concentration of elemental iodine. The choice of a method for the analysis of iodine depends on the concentration range to be deterrnined. 

The relative merits of various MO methods have been discussed in die literature. In general, the ab initio type of calculations will be more reliable, but the semiempirical calculations are faster in terms of computer time. The complexity of calculation also increases rapidly as the number of atoms in the molecule increases. The choice of a method is normally made on the basis of evidence that the method is adequate for the problem at hand and the availability of appropriate computer programs and equipment. Results should be subjected to critical evaluation by comparison widi experimental data or checked by representative calculations using higher-level mediods. Table 1.12 lists some reported deviations from experimental AHf for some small hydrocarbons. The extent of deviation gives an indication of the accuracy of the various types of MO calculations in this application. 

What is actually being measured is the change in concentration of a product or a reactant with time. Many methods have been used to make such measurements." The choice of a method depends on its convenience and its applicability to the reaction being studied. Among the most common methods are... 

Justifications for the use of nonstandard (i.e., nonpreferred or nonpharmacopeial) methods of sterilization may include the heat instability of the active ingredient or an essential excipient. The choice of a method based on filtration through a microbial retentive filter and/or aseptic assembly should be justified, and the appropriate in process controls (including bioburden controls on active ingredients, excipients, bulk solutions, process time constraints etc) discussed in detail in the application. Commercial considerations should not form part of the argument for the application of a nonstandard sterilization process. The highest possible sterility assurance level should be achieved. 

Gardner and Yates [26] developed a method for the determination of total dissolved cadmium and lead in estuarine waters. Factors leading to the choice of a method employing extraction by chelating resin, and analysis by carbon furnace atomic absorption spectrometry, are described. To ensure complete extraction of trace metals, inert complexes with humic-like material are decomposed by ozone [27]. The effect of pH on extraction by and elution from chelating resin is discussed, and details of the method were presented. These workers found that at pH 7 only 1-2 minutes treatment with ozone was needed to completely destroy complexing agents such as EDTA and humic acid in the samples. 

Three methods to derive a state space model for a crystallizer were discussed. The choice of a method in a specific situation depends on the crystallizer configuration, the growth rate kinetics and the variables to be controlled. 

The choice of a method for the preparation of hydrogen bromide will be governed largely by two factors first, the quantity desired and, second, the use to be made of the material, i.e., whether the anhydrous gas or the aqueous solution is desired. Any method for the production of hydrogen bromide gas may be adapted to produce a solution of hydrobromic acid. On the other hand, it is entirely... 

Preparation.—The choice of a method for the preparation of hydrogen in the laboratory is decided by the degree of purity required in the gas, but by suitable means the product obtained by the interaction of a metal and an acid can be sufficiently purified for ordinary use. 

Several physical and chemical methods have been used to follow the course of hydrolysis of proteins. Each method depends upon measurement of the disappearance of protein or the appearance of hydrolytic products during the course of the reaction. The choice of a method depends upon specific factors which are unique to each experimental situation, and one must choose a method in light of the information desired. 

The choice of a method depends on its convenience and its applicability to the reaction being studied. Among the most common methods are... 

The choice of a method for synthesizing a compound derived from a retrosynthetic... 

Grouting is but one of many methods of groundwater control used in construction. The choice of a method for any specific job almost always relates back to economics. Factors that contribute to economical selection include the size of the job, the job location, the operation time schedule, and the contractor s capabilities and experience. The problems described below (which were in these specific cases solved by grouting) should not be considered in general as yielding only to grouting techniques, or only to the specific materials that were used in these actual field jobs. 

The more physical and chemical data there are available for each sample, the more chance there is of selecting the right phase system (and the most suitable detector), thus ensuring success right from the start." Every successful separation adds to the analyst s wealth of experience. To a limited extent the choice of a method can be done by an expert system. ... 

Procedure Starting with 0.2 ml of plasma, prepare a protein-free filtrate by the method of Somogyi (S8). Copenhaver (CIO) has pointed out that the choice of a method for deproteinization which yields an alkaline filtrate is important because of the finding of Wells et al. (W5) that acidic filtrates inhibit trimethylsilylation. 

The choice of a method for the isolation of cell wall material depends on how necessary it is to isolate the CWM with the minimum contamination of intracellular compounds. In Section II. 1 some of the problems involved in the isolation of cell walls have been discussed in general terms. The methods that have been used are illustrated in greater detail by giving some examples of preparing cell walls from different types of tissues. Some of these are subject to the limitations that have been emphasized previously. As representative procedures, however, they indicate the position from which further advances may be made. 

Some fluorine compounds may be prepared by any one of several methods (e.g., NOF from NO+ Fg or from NOBF + NaF), so that the choice of a method of preparation may be based on the availability of starting materials or apparatus. 

Another good choice of a method for converting methylenedioxyphenylacetone to MDA is the Leuckardt reaction. In this case formamide is used instead of N-methyl formamide. When used with phenylacetone to make amphetamine, only the very highgrade 99% material will work. In the case of methylenedioxyphenylacetone, however, the much more commonly available 98% formamide works just fine. See Chem. Abstracts from 1952, column... 

The solubility characteristics of a solute in a given solvent have a considerable influence on the choice of a method of crystallization. It would be useless, for instance, to cool a hot saturated solution of sodium chloride in the hope of depositing crystals in any quantity. A reasonable yield could only be achieved by removing some of the water by evaporation, and this is what is done in practice. On the other hand, a direct cooling crystallization operation would be adequate for a salt such as copper sulphate cooling from 90 to 20 °C would produce about 44 kg of CUSO4 for every 100 kg of water present in the original solution. As the stable phase of copper sulphate at 20 °C is the pentahydrate the... 

A major technical consideration in DNA-DNA hybridization is choice of a method for determining the amount of DNA which is single-stranded and double-stranded at various temperatures. Two methods have been most often employed the binding of double-stranded DNA to HAP (hydroxylapatite) and digestion with the enzyme SI DNA nuclease which cleaves single-stranded DNA into mono-nucleotides. We detail our procedures for the latter method in another chapter in this volume (Caccone and Powell). 

The choice of a method for the analysis of water in a given sample is dependent on the nature of the sample and the manner in which the water is associated with that sample. The factors that should be considered are listed in Table 1. 

Stakes. Eventually, method selection also depends on the stakes. In a business context, it would indeed make sense to adapt the choice of a method to the importance of expected results for decision making. Not respecting this rule could lead to overwhelmed sensory resources and misuse of sensory measures. This goes along with prioritization. The key advice is to discipline yourself in order to avoid comfort and routine, and always to challenge the needs. Always go for simpler methods, and use more sophisticated methods only when there is a real need. Additionally, it is important to educate your stakeholders so that they understand that not aU demands are addressed with the same method. 

All the three groups of IC methods recently developed (based on conductivity, UV/Vis, and MS detection modes, respectively) yield comparable results and comply with the requirements of the international directives concerning inorganic oxyhalide by-products in drinking water. " The future application and choice of a method will depend on the equipment available in the laboratories, as well as the number and kinds of samples to be analyzed. 

In our experience, the choice of a method is greatly dependent on the type of stopper. A pharmaceutical company must determine the moisture removal and retention properties of a given stopper on an individual... 

Reason divided error into slips, or lapses, and mistakes. Slips or lapses involve the correct choice of a method to achieve a task, but a failure to carry it out correctly. Mistakes on the other hand involve a flaw in the plan which means that even if it is carried out correctly, the objective isn t achieved. Slips and lapses are often skill-and rale-based errors, whereas mistakes are often knowledge-based errors. 

The author suggests the use of the above classifications to aid the choice of a method for system analysis. One other categorisation of complexity defines two types essential and accidental. 

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