Quantitative methods utilization

This valuable method utilizes the O-TMS enol ethers derived from either pentane-2,4-dione or methyl acetoacetate, the former being the more reactive. Even t-alcohols are rapidly and quantitatively silylated in DMF at room temperature. A similar technique can be used to introduce the TBDMS group, although here ptsa catalysis is required (4). 

With the development of accurate computational methods for generating 3D conformations of chemical structures, QSAR approaches that employ 3D descriptors have been developed to address the problems of 2D QSAR techniques, that is, their inability to distinguish stereoisomers. Examples of 3D QSAR include molecular shape analysis (MSA) [26], distance geometry,and Voronoi techniques [27]. The MSA method utilizes shape descriptors and MLR analysis, whereas the other two approaches apply atomic refractivity as structural descriptor and the solution of mathematical inequalities to obtain the quantitative relationships. These methods have been applied to study structure-activity relationships of many data sets by Hopfinger and Crippen, respectively. Perhaps the most popular example of the 3D QSAR is the com-... 

A reliable chromatographic method has been developed for the quantitative aneilysis of hydrophobic impurities in water-soluble polymeric dyes. The method utilizes both the molecular sieve effect of normal gel permeation chromatography and solute-column packing interaction, modified by solvent composition. This method eliminates the need to extract the impurities from the polymeric dye with 100 extraction efficiency, as would be required for an ordinary liquid chromatographic analysis. 

By a traditional method, a- and /i-iononcs can be converted to ionene, catalyzed by HI along with small amounts of phosphorus. A cleaner cydization occurred by heating /i-ionone in water at 250 °C in the MBR [50]. In the workup the usual exhaustive washing procedures were unnecessary. Similarly, as mentioned above, carvacrol was prepared almost quantitatively, by isoaromatization of carvone in water at 250 °C for 10 min [47]. A conventional, literature method utilized acidic conditions, took a longer time and proceeded in lower conversion. The above examples show that elevated temperatures under neutral pH conditions can offer advantages over acidic (or basic) reagents at lower temperatures. 

Electron spin resonance, nuclear magnetic resonance, and neutron diffraction methods allow a quantitative determination of the degree of covalence. The reasonance methods utilize the hyperfine interaction between the spin of the transferred electrons and the nuclear spin of the ligands (Stevens, 1953), whereas the neutron diffraction methods use the reduction of spin of the metallic ion as well as the expansion of the form factor [Hubbard and Marshall, 1965). The Mossbauer isomer shift which depends on the total electron density of the nucleus (Walker et al., 1961 Danon, 1966) can be used in the case of Fe. It will be particularly influenced by transfer to the empty 4 s orbitals, but transfer to 3 d orbitals will indirectly influence the 1 s, 2 s, and 3 s electron density at the nucleus. 

Quantitative solid state 13C CP/MAS NMR has been used to determine the relative amounts of carbamazepine anhydrate and carbamazepine dihydrate in mixtures [59]. The 13C NMR spectra for the two forms did not appear different, although sufficient S/N for the spectrum of the anhydrous form required long accumulation times. This was determined to be due to the slow proton relaxation rate for this form. Utilizing the fact that different proton spin-lattice relaxation times exist for the two different pseudopolymorphic forms, a quantitative method was developed. The dihydrate form displayed a relatively short relaxation time, permitting interpulse delay times of only 10 seconds to obtain full-intensity spectra of the dihydrate form while displaying no signal due to the anhydrous... 

An automated colorimetric assay for the quantitation of the separate components of neomycin (B, C and neamine) has also been reported- - . The method utilizes a separation of the components on a column of carbon and Kieslguhr G (4 1). The column eluate is reacted with nin-hydrin to determine the amounts of neomycin B, C and neamine. 

With the advent of API sources, LC/MS/MS allows the facile development of quantitative methods that are sensitive, selective, robust, and amenable to the rapid analysis of a majority of small molecules. In order to achieve high-throughput bioanalysis in support of pharmacokinetic studies, many approaches have been reported utilizing automated sample preparation and reducing analysis time by pooling samples, parallel analysis, and fast chromatography. 25,26,152,153... 

Adenosine triphosphate is utilized in portions of the cell other than the mitochondria and chloroplasts therefore, the utilization as well as the production of ATP is of importance to total adenylate status. As a result, it became important to consider total ATP content of plants. When detached pinto bean leaves were exposed to 1,0 yl/1 ozone for 30 min total ATP content of the leaf decreased (12), Since ozone altered leaf ATP content it could also alter the leaf s adenylate status we wished to determine if a correlation existed between alteration in adenylates and the change previously reported in photosynthesis and respiration. Since ATP is readily broken down by adenosine triphosphatases, a reliable method of extraction and quantitative method of ATP analysis was designed for the study (8),... 

Quring the past several years coal petrography has gained acceptance in certain areas of coal utilization, preparation, and mining as a useful analytical tool. The rapid evolution of this analytical technique can be attributed to the development and subsequent refinement of quantitative methods for measuring the reflectance characteristics of vitrinite in coal (8, 14, 15, 16). Mean maximum reflectance has been shown to be directly related to coal rank (14, 16). Moreover, it is known that rank is important in determining certain carbonization and chemical properties. 

Taylor CR, Levenson RM Quantification of immunohistochemical - issues concerning methods, utility and semi-quantitative assessment II. Histopathology 49 411-24,2006. 

A quantitative method was reported by Maslova for the determination of acetylcholine in biological tissues by polarographic analysis utilizing a rotating platinum electrode [18]. The principle of the method is based upon a polarographic analysis of the iron ions which remain after the formation of a specific Fe-acetylhydroxamic acid complex. Using this method, it was shown that 1 mL of peripheral blood of a healthy adult man contained 6.6 ng of acetylcholine. 

Determination of free 4-hydroxy-2,3-trans-alkenals by HPLC Esterbauer (1982) has developed a procedure for the qualitative detection and quantitative measurement of steady-state concentrations of free hydroxyalkenals (specifically HNE) in tissues, tissue extracts and lipid containing foodstuffs. Their method utilizes UV-detection of the free aldehyde at its 220 nm UV-absorption maximum and peak identification was confirmed by mass spectrometry. An effective purification and concentration step is employed using dichloromethane to extract hydroxyalkenals from samples trapped on Extrelut columns. The samples are subsequently purified by solid-phase extraction on octadecyl-bonded silica (ODS) disposable cartridges and then analysed by HPLC. 

The usual method utilized to identify the clay minerals in coal is X-ray diffraction of the low-temperature ash (LTA), but because of the poor crystallinity of the clays in the coal, the technique cannot be used for quantitative measurements. The Mossbauer effect does not provide much improvement owing to the small iron content of the clays. A coal rich in clays is shown in Figure 7 (about 10% mineral matter). The two peaks at higher... 

A new colorimetric procedure has been developed for the quantitative measurement of atmospheric ozone. The specific, sensitive, and reproducible nonaqueous method utilizes the rate of color produced on ozonization of o-dichlorobenzene solutions of N-phenyl-2-naphthylamine. The color reaction conforms to Beer s law and has a practical sensitivity of 1.8 X 10 mg. of ozone. Oxygen and oxides of nitrogen, in concentrations greater than those normally occurring in the atmosphere, do not interfere with the chromogenic reaction. 

So, the methods characteristic of each test, comprising taken together a type of tests, must undergo validation testing of their results. This is the implementation of the method, and the establishment of a standard for its performance. For the standardization of quantitative methods, this consists at a minimum of a determination of trueness when blank utilization, certified reference materials (or reference materials, or spiking materials) or collaborative trials are used, repeatability (r) with repetition,... 

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