Determination spectral methods

DETERMINATION OF MACRO- AND MICROELEMENTS IN BIOLOGICAL SAMPLES BY ATOMIC SPECTRAL METHODS... 

The molybdenum, tungsten and tantalum concentration influence on LCD nickel-ferrous HRS resistance, used for gas turbine installations parts is investigated. The tests were carried out on modeling compositions. Samples were molded on the basis of an alloy of the ZMI-3C. The concentration of tantalum varied from 0 up to 5% with a step of 0,5%. The contents of elements were determined by a spectral method. 

Molten salt investigation methods can be divided into two classes thermodynamic and kinetic. In some cases, the analysis of melting diagrams and isotherms of physical-chemical properties such as density, surface tension, viscosity and electroconductivity enables the determination of the ionic composition of the melt. Direct investigation of the complex structure is performed using spectral methods [294]. 

DI methods tend to produce even-electron ions such as protonated molecules [M + H]+, or cationised molecules such as [M + Na]+ these stable ions undergo only a minimum amount of fragmentation. Desorption/ionisation mass-spectral methods (in particular FD, EH and LD) may be used for determining molecular... 

The progress of polymer degradation may be followed by a wide variety of techniques, some of them being mentioned at the right column in the Bolland-Gee scheme (Scheme 2). There are techniques that directly monitor some of the elementary reaction steps such as, for example, oxygen absorption (reaction 2), differential scanning calorimetry (DSC) (reaction 3), chemiluminescence (reaction 11) analytical and/or spectral methods of determination of hydroperoxides, etc. 

The structure of the complexes in solution and in crystals was established using spectral methods and by comparison with the data for initial ligands. This approach made it possible to determine the structure of new ligands formed in the reaction by complexation. 

During the Western Project, a total of 3000 grab samples were assayed by using the rapid spectral method to determine 32 elements and chemical adsorption to determine gold. Spectral assay data were processed in order to determine the distribution of 24 elements. Background (Cf) values were calculated using Lognormal Statistics software. 

If an investigator remains concerned about the substrate purity following repurification procedures and subsequent analysis, then a number of other approaches may be considered. For example, different lots of substrate could be analyzed with the enzyme to learn if identical kinetic parameters are obtained. If one has some idea as to the identity of the possible contamination, then the impurity can be added to the stock substrate solution at a known amount and the accuracy of the kinetic parameters in the presence of the adduct can be assessed. Since the researcher already knows the degree of sensitivity of the various chemical, enzymatic, and/or spectral methods used to assess substrate purity, this known addition provides a means for determining the maximum amount of impurity present. Combined with the observations seen with the known addition of the impurity, such information will provide an idea on the level of accuracy of the kinetic parameters. 

Stability constants, from which AG° values are calculated, provide a direct measure of the extent of complexing in solution, and these values have been used to determine cation selectivity by macrocyclic compounds. Several of the methods commonly used to determine log K values cannot be used with many of these systems. Thus, procedures based on change in hydrogen ion concentration (pH titration, hydrogen electrode, etc.) cannot be used in those cases where the ligand is uncharged and its concentration is not pH dependent. Spectral methods generally have not been used because of the usual lack of favorable absorption characteristics by the compounds, cations or cation-complexes in the cases studied. 

This is an additive constitutive property that is easy to determine experimentally and has theoretical significance, but it has been superceded by spectral methods that offer a deeper... 

This is an additive constitutive property that is easy to determine experimentally and has theoretical significance, but it has been superceded by spectral methods that offer a deeper insight into the molecular structure. Nevertheless, it has historical value in the early elucidation of the structure of secondary ozonides as substituted 1,2,4-trioxolanes . ... 

Ozonolysis of alkenes (end of Section 6.4) and cleavage of glycols (Section 14.11) afford carbonyl compounds. These reactions, once used for structure determinations, have been superseded by spectral methods. 

Epoxy-latrunculin A (478) and latrunculin M (479) were isolated from L. magnified. The structures were established by chemical and spectral methods [408]. Latrunculin A (205) was isolated from Fasciospongia rimosa collected in Okinawan waters and the absolute configuration was determined by X-ray analysis [409]. F. rimosa also contained the cytotoxic latrunculin S (480) and the structure was elucidated by NMR spectroscopy and chemical correlation with known congeners [410]. 

Whereas zwitterionic forms may be invoked to explain the properties of 2- and 4-thiopyrones, the 3-thiopyrone can only exist as the betaine (42) and is therefore to be compared with the pyridinium system for a bonding and structural likeness. A theoretical treatment (73JPR690) has been published using CNDO/2 methods, and the calculated parameters were found to agree well with experimentally determined spectral properties. 

Diethyl dithioacetals have been used for determining the position of the acetamido group in acetamido sugars by the mass-spectral method.40... 

Tables 6.3-6.5 record data developed to undertake structural analysis in systems possessing chromophores that are conjugated or otherwise interact with each other. Chromophores within a molecule interact when linked directly to each other or when they are forced into proximity owing to structural constraints. Certain combinations of functional groups comprise chromophoric systems that exhibit characteristic absorption bands. In the era when UV-VIS was one of the principal spectral methods available to the organic chemist, sets of empirical rules were developed to extract as much information as possible from the spectra. The correlations referred to as Woodward s rules or the Woodward-Fieser rules, enable the absorption maxima of dienes (Table 6.3) and enones and dienones (Table 6.4) to be predicted. When this method is applied, wavelength increments correlated to structural features are added to the respective base values (absorption wavelength of parent compound). The data refer to spectra determined in methanol or ethanol. When other solvents are used, a numerical correction must be applied. These corrections are recorded in Table 6.5.

Alchorneine (C12H19ON3 mp 43° [a]D — 105°) was isolated from the above-named plant as well as from A. hirtella Benth. Its structure (6), largely determined by spectral methods including an X-ray examination of its methiodide, was confirmed by chemical degradation to recognizable... 

Argentine (9) and argentamine (10) are two new alkaloids whose structures were determined by spectral methods (4). 

Gymnamine (C19H2603N2 amorphous picrate, mp 260°) has structure 101 as determined by spectral methods. Hydrolysis followed by Wolff-Kishner reduction converted it into lycodine (102) (77). 

In addition to the known alkaloids from this plant the trunk bark yielded the new hernandonine (C18H905N mp > 280°) whose structure (109) was determined largely by spectral methods and confirmed by its synthesis from N-methylhernovine by known reactions (88). 

The structure of this base (142) was determined by spectral methods and the aldehyde portion was converted to carboxyl by oxidation with silver oxide ISO). 

The structure of the alkaloid propyleine (C13H21N amorphous levorotatory) (156) from this beetle was determined by spectral methods supplemented by chemical methods. It is the dehydro derivative of coccinellin (143) into which it was converted (144). 

The literature dealing with alkaloids shows no obvious signs of abatement. The classic methods of the organic chemist employed in structural determinations have evolved into spectral methods, and chemical reactions are involved largely in confirmatory and periferal studies. Inasmuch as the spectral methods have become largely standardized we incline to limit the details in these volumes. 

Ultraviolet Spectrophotometry Pentazocine can be determined in pentazocine hydrochloride tablets by a UV spectral method. The sample is extracted with sulfuric acid, basified, extracted with ether and back-extracted into 1 in 70 dilute sulfuric acid. The absorbance of the solution in 0.5 N H2SO1L is determined at 278 nm and compared to that of the standard preparation. A cation exchange column isolation method can be utilized to determine pentazocine in pentazocine lactate injection. Pentazocine is eluted from the column with methanol 6 N HC1 (1 1). Sample absorbance is read at 278 nm and compared to a pentazocine standard at approximately 120-w.g/ mL (3). 

Treatment of aromatic carboxaldehyde (diaminomethylene)hydrazones (105) with hot acetic anhydride or benzoyl chloride affords l,4-diacyl-3-acylamino-5-ary 1-4,5-dihydro- 1H-1,2,4-traizoles (106) in 75-95% yields. In contrast, when the 4-pyridine analog of 105 was employed, the unusual hemianimal triazole derivative (107) was obtained. The structures of the novel compounds were determined by spectral methods and in several cases by x-ray structural analysis. Mechanistic considerations are discussed [95M733]. The oxazole-1,2,4-triazole (108) was prepared by cyclization of the corresponding oxazolecarbonyl-thiosemicarbazide with bicarbonate, alkylation at the sulfur and oxidation to the sulfoxide with MCPBA [95JHC1235]. 

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