Quantitative precision

It may be mentioned in passing that the volume, and quantitative precision, of data available in this field owes much to the use of gas/ liquid chromatography for the rapid, and accurate, quantitative analysis of alkene mixtures. 

There also exists an alternative theoretical approach to the problem of interest which goes back to "precomputer epoch" and consists in the elaboration of simple models permitting analytical solutions based on prevailing factors only. Among weaknesses of such approaches is an a priori impossibility of quantitative-precise reproduction for the characteristics measured. Unlike articles on computer simulation in which vast tables of calculated data are provided and computational tools (most often restricted to standard computational methods) are only mentioned, the articles devoted to analytical models abound with mathematical details seemingly of no value for experimentalists and present few, if any, quantitative results that could be correlated to experimentally obtained data. It is apparently for this reason that interest in theoretical approaches of this kind has waned in recent years. 

Migration characteristics very sensitive to conditions thin layers easily damaged quantitative precision only moderate 5-10%. 

TI is a very precise and accurate method in stable isotope ratio measurements and quantification of inorganic elements, for example, by isotope dilution mass spectrometry [8]. Because TI is a continuous ion source, it could be coupled to any analyzer that is suitable for such sources. However, because the strength of TI lies in the quantitative precision and accuracy, sector analyzers are preferred to ensure maximum quality. 

In 1950 an alternative to the Sanger procedure for identifying N-terminal amino acids was reported by Edman—reaction with phenyl-isothiocyanate to give a phenylthiocarbamide labeled peptide. When this was heated in anhydrous HC1 in nitromethane, phenylthiohy-dantoin was split off, releasing the free a-NH2 group of the amino acid in position 2 in the sequence. While initially the FDNB method was probably the more popular, the quantitative precision which could be obtained by the Edman degradation has been successfully adapted to the automatic analysis of peptides in sequenators. 

Thome, G.C. Gaskell, S.J. Payne, P.A. Approaches to the Improvement of Quantitative Precision in SIM High Resolution Applications. Biomed Mass Spectrom. 1984,77,415-420. 

Easily controlled and precise sample introduction ensures quantitative precision. 

Samples of the red clay having uniform physical and chemical characteristics were provided by G. R. Heath of the University of Rhode Island. The samples were obtained from core LLUU-GPC-2, collected on October 11, 1976, at 30° 20.9 n, 157° 50.85 w, water depth 5821 meters, and are representative of the smectite-rich region of the red clays which occurs in the sediment at depths below about ten meters. In this region, the sediment appears to contain about five to six percent by weight leachable iron and manganese in the form of hydrous oxides. The remaining material appears to be dominated by iron-rich smectite and lesser, varying amounts of phillipsite (2). The results of a semi-quantitative (precision in data is within a factor of 2) elemental analysis... 

In some kinds of work, such as identification or semiquanti-tative screening, no great quantitative precision is either available or expected. Good planning would tend away from expensive integrators unless the volume of samples and paperwork made automation attractive. 

By contrast, colorimetry is relatively simple and inexpensive. Procedures exist not only for all the metals but for many nonmetallic constituents and organic compounds. It is undoubtedly the most widely applied technique in trace analysis, and the colorimeter or spectrophotometer tends to be the work-horse of the laboratory. Sensitivities are astonishingly great, and quantitative precision varies from a few percent... 

ASTM-Task Group E1908, An evaluation of quantitative precision in high-performance liquid chromatography, J. Chromatogr. Sci., 19 338 (1981). 

BLS). This paper describes a novel and alternative method for performing DCP analyses and in particular a new procedure for the formation of the spin fluid density gradient external to the DCP disc. This new patented method ( 3), known as the External Gradient Method (EGM), will be compared to the BLS method of analysis. The quantitative precision of the results obtained with EGM and BLS will be compared by statistical analysis.In addition, qualitative advantages of the EGM over the BLS method will be given. 

Internal standards usually improve quantitative precision because injection bias is compensated for. If the internal standard elutes at the correct migration time... 

On another level, the story of hydrogen reveals how science is conducted. Physical theories are created to provide explanatory schemes whereby the observed world can be understood with quantitative precision. Those theories that capture the support of scientists are those that allow detailed predictions to be made and lead to new insights into the natural world. Good theories are simple theories that unite disparate realms of experience. Physical theories, however, must always yield to the demands of experimental data. Experimental facts are incontrovertible. If they are not accommodated by theory, the theory is held in question. Theories, good theories, are not quickly abandoned. Strenuous effort is exerted to refine a good theory so that experimental facts can be explained. In the final analysis, however, experimental results, once tested and retested, once verified by independent experimental methods, ultimately rule. Dirac s theory was elegant and beautiful, but in the face of data from Lamb and Rabi, it fell short. Their data then became the stimulus for the more powerful theory of quantum electrodynamics. 

It is also of advantage to use a detection method that is both as sensitive and as linear as possible, in order to achieve a quantitative analysis possible and to limit the amount of sample consumed. In this respect, it is important to underscore that the quantitative precision of proteomic analysis is in the range of 10%, which permits the detection of small variations in protein amount with a good statistical confidence (usually twofold differences). 

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