Methods competing

Time, Cost, and Equipment In comparison with competing methods, potentiome-try provides a rapid, relatively low-cost means for analyzing samples. Commercial instruments for measuring pH or potential are available in a variety of price ranges and include portable models for use in the field. 

Further processing of the enriched NO2 with different and competing methods—some requiring low temperature and others requiring high... 

At the central platform, water and hydrocarbon liquids are first removed in knockout drums. Then saturated natural gas, free of any liquid droplets, enters the twin expanders. The gas is cooled below its dewpoint, allowing heavy hydrocarbon components and water vapor to condense in the discharge stream. Turboexpanders were chosen for two main reasons They are more compact than competing methods of controlling the dewpoint and their operating costs are typically lower than those of many alternatives. 

Like XPS, the application of AES has been very widespread, particularly in the earlier years of its existence more recently, the technique has been applied increasingly to those problem areas that need the high spatial resolution that AES can provide and XPS, currently, cannot. Because data acquisition in AES is faster than in XPS, it is also employed widely in routine quality control by surface analysis of random samples from production lines of for example, integrated circuits. In the semiconductor industry, in particular, SIMS is a competing method. Note that AES and XPS on the one hand and SIMS/SNMS on the other, both in depth-profiling mode, are complementary, the former gaining signal from the sputter-modified surface and the latter from the flux of sputtered particles. 

Quantum mechanics provide many approaches to the description of molecular structure, namely valence bond (VB) theory (8-10), molecular orbital (MO) theory (11,12), and density functional theory (DFT) (13). The former two theories were developed at about the same time, but diverged as competing methods for describing the electronic structure of chemical systems (14). The MO-based methods of calculation have enjoyed great popularity, mainly due to the availability of efficient computer codes. Together with geometry optimization routines for minima and transition states, the MO methods (DFT included) have become prevalent in applications to molecular structure and reactivity. 

TABLE 2 Target Chemotypes, the Corresponding CE Technique and Competing Methods... 

The next great chemist to take up the challenge of making other human steroids was the Austrian-born Carl Djerassi, who fled his coimtry after the Nazi invasion in iggS, and joined the Swiss owned CIBA company in New York. He subsequently joined Syntex (now a respectable company after that shady start) and devised a way of making cortisone from extracts of Mexican yams or sisal. However, the Syntex synthesis of cortisone was never commercially successful because a competing method, involving the use of microbial fermentation, could provide a cheaper product. 

The purpose of a written analytical procedure must be to convey the instructions necessary to allow a competent analytical chemist to reproduce the procedures and measurement processes faithfully, to apply the method to their sample and to state the results with appropriate confidence. I stress the word competent. Method transfer can only be accomplished between appropriately trained and qualified personnel. There is an unfortunate belief, in some quarters, that if procedures are written in an all-embracing and exhaustively detailed manner then professionally trained and qualified staff are not always necessary. This is a dangerous and misguided belief. 

There are many—often conflicting—claims of the best chemometric method chosen for a given application. Those who make such claims sometimes characterize the competing methods in not very flattering terms. How would you settle the beauty contest among various multivariate analysis evaluation methods ... 

NMR and crystallography should be viewed as complementary rather than competing methods. Different kinds of structural information can be obtained, and information gleaned from one technique can aid in the process for the other. Still, NMR is the younger sister in the family and must meet a higher standard of proof to justify big spending and job security in corporate research and development. 

Despite the interesting biological properties of this class of natural products, few competent methods for the chemical synthesis of bergenin and its derivatives exist. Schmidt and coworkers reported a ten step synthesis of 8,10-di-C-... 

While plasma-enhanced methods are very usefiil to lower the substrate temperature, the as-deposited films are typically less conformal and often contain more surface impurities than competing methods. In this method, reactive radicals, ions, and atoms/molecules are formed in the gas phase that interact with the relatively low-temperature substrate to generate a film. Some of the more recent applications for plasma CVD include growth of cubic boron nitride (c-BN) thin films. 

One could use the method of electrolysis to separate other iso-topes, for instance, to produce O, but the separation factors are low, and the method is not expedient, unless the product has a very high value and other competing methods of separation (e.g., gas diffusion) cannot be used for one reason or another. 

Radioisotope instruments became available for all kinds of measurements just when the trend towards automation in industry was strong. Radioisotope instruments can perform certain measurements such as mass per unit area which cannot be made by other equipment. For other measurements, like level or distance, there are now other competing methods available. 

The total yield of the oxidation of toluene to phenol varies according to the technology and operating conditions, from between 75 and 80 molar per cent in the liquid phase to between SO and 85 per cent in the vapor phase. Its economics in comparison with competing methods, including the cumene method, which is the most widespread and shows the highest performance, depends closely on the price differential existing between the raw materials employed (benzene and toluene). 

Reverse osmosis will have a lower energy requirement than most competing methods of separation, since its woik requirement differs from the minimum work of separation only by the ratio Plr. However, it is limited to modest concentration of veiy dilute solutions because the osmotic pressure becomes quite large... 

The differential pulse and square wave techniques are among the most sensitive means for the direct evaluation of concentrations, and they find wide use for trace analysis. When they can be applied, they are often far more sensitive than molecular or atomic absorption spectroscopy or most chromatographic approaches. In addition, they can provide information about the chemical form in which an analyte appears. Oxidation states can be defined, complexation can often be detected, and acid-base chemistry can be characterized. This information is frequently overlooked in competing methods. The chief weakness of pulse analysis, common to most electroanalytical techniques, is a limited ability to resolve complex systems. Moreover, analysis time can be fairly long, particularly if deaeration is required. 

Compared to the competing methods of gas-liquid chromatography (GLC) and liquid-solid chromatography, gas-solid cbrorftatography (GSC) is today of minor importance in the separation of Organic compounds. GSC techniques were in use prior to the introduction of GLC in 1952 [see review of Ref. (7)], but the latter method quickly displaced almost all interest in separations by GSC. Within the past 5 years there has been a widespread renewal of interest in GSC for the separation of organic samples, but the future role of GSC in this area is still not clear. 

In modern clinical practice, competing methods for measuring the same or similar parameters are used and parameters are preferred that have been proved to be easy to apply and reliable in everyday use. Nevertheless, several methods are usually used simultaneously as the resulting parameters yield similar data on the same organ. Apart from changing opinions on approved parameters and the development of new procedures, the selection to methods depends on the intended application and the information needed. In addition to global parameters, supplementary parameters exist which are used jointly to compose a detailed picture. 

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