Substituted pyridines

5-Methyl-4-phenyl-2-styryipyridine has been oxidized to 5-methyl-4-phenylpyridinie-2-carboxylic acid. The decarboxylation of this acid has given 3-methyl-4-phenylpyrldine. To prove the structure of -(5-methyl-4-phenyl-2-pyridyl)acetophenone, it has been converted into 2, 5-dimethyl-4-phenylpyridine. The reaction of benzyl chloride with the lithium derivative of 2, 5-dimethyl-4-phenylpyridine has been studied. 3,7-Dimethyl-2-azafluorene has been obtained from 2,5-dimethyl-4-p-tolylpyridine.     

Determination of the elemental composition of cyanobacteria cells and cell fractions by atomic emission and atomic absorption spectrometry

An approach to studying the elemental composition of cyanobacteria Spirulina platensis and Nostoc commune using a set of complementary analytical methods (ICP-AES, PAAS, and ETAAS) is proposed. The procedures were adapted for the determination of macro- and microelements (Na, K, Mg, Ca, Fe, Mn, Cu, Mo, Zn, B, and Se) in the biomass of cyanobacteria and separated cell fractions (chloroform and water-methanol extracts and precipitates). The conditions for the mineralization of biological materials were optimized for autoclave and microwave sample preparation procedures. The evaporation and atomization of Se and Mo in a graphite furnace in the presence of chloroform and methanol were studied. The use of combined analytical methods and the interpretation of analytical results allow one to draw conclusions about the ability of cyanobacteria to accumulate biologically important microelements (B, Mo, Se, and Zn) and to optimize technological processes for manufacturing biologically active substances.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 1, 2005, pp. 35–40.Original Russian Text Copyright © 2005 by Sedykh, Lyabusheva, Tambiev, Bannykh.     

Ascorbic acid as a matrix modifier for determination of tin in concentrated boric acid solutions by electrothermal atomic-absorption spectrometry

It has been found that the atomic-absorption signal for tin is reduced in the presence of 5 micro1 of 0.05-0.30M boric acid at STPF-conditions. It has been proposed that the reason for the boron interferences is the formation of SnB(g) at the atomization stage. In the presence of palladium chloride the interferences from 0.2M boric acid are reduced by a factor of 1.3. The interferences are reduced most effectively when the sample is atomized from a polycrystalline graphite platform or in the presence of ascorbic acid. The interference of up to 0.2M boric acid can be suppressed and the area of the tin signal doubled. It is proposed that the observed phenomenon is connected with the bonding of boron as non-volatile B(4)C. Ascorbic acid is the most effective matrix modifier for the determination of different trace elements in boron compounds.     

Minimizing the effect of organic matrices in the analysis of tin-containing extracts by electrothermal atomic absorption spectrometry: Determination of Tin in rocks

The effect of the nature of the extracted complex and of the organic solvent on the sensitivity of the extraction/atomic absorption determination of tin in a graphite-furnace atomizer is investigated. It is recommended that extracts of tin as its chloride complex, or chelates with N-benzoyl-N-phenylhydroxylamine or 8-quinolinol, in organic solvents which do not contain chlorine should be used. The depressive effect of the organic matrix can be significantly decreased by using ascorbic acid as matrix modifier, by atomization from a graphite platform, and by using an atomizer coated with tungsten carbide. The procedure developed is applied to the determination of tin in rocks. For tin concentrations of 0.1–10 μg g^?1, the relative standard deviation does not exceed 10%.     

Factors influencing the free oxygen content in an electrothermal atomizer

A considerable decrease in the partial pressure of free oxygen in the gas phase within a graphite atomizer during atomization with the use of ascorbic acid as a matrix modifier was proved by using the method suggested by L'vov and Ryabchuk. A similar change in the gas-phase composition was observed in graphite tubes treated with compounds of refractory metals. A mechanism for this oxygen binding is suggested. It is shown that the sensitivity of the determination of tin is improved by decreasing the free oxygen content of the gas phase.     

Oxidation of p-cresol with ozone in acetic anhydride

Preparation of aromatic alcohols and aldehydes by oxidation of p-cresol with ozone in acetic anhydride in the presence of sulfuric acid, manganese acetate, and potassium bromide was studied. The optimal oxidation conditions were determined.     

Effects of plasmonic absorption of terahertz radiation in silica nanocomposite doped with erbium silicate

This paper studies terahertz transmission spectra of silicon and erbium silicides which can be used to create uncooled bolometers for terahertz frequency domain.