Kinetic studies of antimony and selenium atomization processes including a chemical modifier during their determination by electrothermal atomic absorption spectrometry

We have studied antimony and selenium atomization processes including a chemical matrix modifier (palladium-containing activated carbon) during their determination by electrothermal atomic absorption spectrometry. We have developed and fine-tuned an experimental setup for determining the kinetic characteristics (activation energy and frequency factor) for element atomization processes from measurements in the initial section of the analytical signal. We provide a rationale for the most likely mechanism for the interactions that occur. The results of the kinetic studies of the atomization processes showed that the modifier we developed was highly effective, as a result of formation of a thermally stable condensed system C-Pd-A (where A is the analyte). __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 530–534, July–August, 2006.     

Preparation and properties of silica gel with immobilized formazan group

A new sorption material, silica gel with covalently immobilized formazan group, was suggested and characterized. The material was prepared by coupling the immobilized aryldiazonium salt with benzaldehyde phenylhydrazone. The equilibrium and kinetic characteristics of the sorption of Cu(II), Co(II), Ni(II), and Cd(II) from solutions onto the modified silica gel were determined. The material proved to efficiently concentrate Cu(II) from multicomponent solutions. The coordination surrounding of Cu(II) in the complex on the sorbent surface was determined by ESR.     

Determination of Polycyclic Aromatic Hydrocarbons in Soils and Bottom Sediments by Gas Chromatography–Mass Spectrometry with QuEChERS Sample Preparation

Journal of Analytical Chemistry - The work is dedicated to the determination of polyaromatic hydrocarbons (PAHs) in soils and bottom sediments by gas chromatography–mass spectrometry using...     

Stereoselective synthesis of unnatural α-amino acid derivatives through photoredox catalysis

A protocol for stereoselective C-radical addition to a chiral glyoxylate-derived N-sulfinyl imine was developed through visible light-promoted photoredox catalysis, providing a convenient method for the synthesis of unnatural α-amino acids. The developed protocol allows the use of ubiquitous carboxylic acids as radical precursors without prior derivatization. The protocol utilizes near-stoichiometric amounts of the imine and the acid radical precursor in combination with a catalytic amount of an organic acridinium-based photocatalyst. Alternative mechanisms for the developed transformation are discussed and corroborated by experimental and computational studies.

A protocol for stereoselective C-radical addition to a chiral glyoxylate-derived N-sulfinyl imine was developed through visible light-promoted photoredox catalysis, providing a convenient method for the synthesis of unnatural α-amino acids.     

Identification of wine provenance by ICP-AES multielement analysis

We have estimated the possibility of identifying the provenance of some natural wines produced in the Krasnodar region. The macro- and microelement composition of wines and soils from the place of grape origin has been used as the classification criterion. The main elements indicating the wine provenance, Al, Co, Cu, Mn, Ti, Zn, Ba, and Rb have been determined by inductively coupled plasma atomic emission spectroscopy. We have revealed the possibility of distinguishing wines by their brand and provenance using pair-wise comparison of the classification function parameters for soils and wines produced from grape grown on those soils.     

Indirect voltammetric determination of total surfactants in waters

The effect of anionic, cationic, and nonionic surfactants on anodic peaks of metals in their voltammetric determination was studied. It was shown that the total of synthetic surfactants in waters can be determined. Neonol was chosen as a reference substance for the determination of synthetic surfactants in solution; zinc and cadmium were chosen as reference elements     

Identification of (2-aminopropyl)benzofuran and its metabolites in human urine

An HPLC?HRMS method for the detection of the benzofuran analog of amphetamine and its metabolites in human urine using both library search and target search of the most probable metabolites based on their calculated accurate weights and fragmentation regularities is proposed. The proposed method is confirmatory. Gas chromatography–electron impact mass spectrometry with library search is proposed as the main screening method.     

On the limitation of the term <Emphasis Type="Italic">petroleum products</Emphasis> in the determination of the oil pollution of bottom sediments

Problems related to the determination of the oil pollution of bottom sediments are discussed. Tarry substances resistant to degradation, whose content can be as high as 50% on a total oil basis, are accumulated in the bottom sediments. The conventional term petroleum products, which implies only a hydrocarbon fraction, does not adequately describe these substances; because of this, the really evaluated level of the oil pollution of bottom sediments becomes underestimated to a considerable degree. We proposed to determine tarry substances in bottom sediments by fluorescence spectrometry at 490–510 nm in combination with a stage of the chromatographic preconcentration and separation of oils and petroleum products into the following main group components: hydrocarbons, tars, and asphaltenes. The substances coextracted with the petroleum products (pesticides, phenols, pigments, etc.) occurred in a chromatographic zone of tars and asphaltenes, but they fluoresce at other wavelengths and do not interfere with the determination. The typical chromatograms of hydrocarbons from the bottom sediments of different water bodies obtained by gas chromatography are given.     

气相色谱法探究聚醚醚酮的热降解及热氧化降解（英文）

Poly(ether ether ketone)(PEEK)was synthesized via polycondensation of hydroquinone with 4,4′-difluorobenzophenone at 320℃for 5 h.Thermal and thermo-oxidative degradation of PEEK was studied over a wide range of temperatures.In an inert medium,decomposition of the polymer occurred in one stage,with the formation of a coke residue accounting for approximately 50%of the original polymer mass.In air,the mass loss curve exhibited two distinct stages.The first stage involved breakdown of the main polymer chain,the speed of which indicated a radical chain failure mechanism.In the second stage,the rate of mass loss clearly decreased,indicating a transition from the radical chain failure mechanism to simple combustion reactions(wherein the polymer combusted completely).To further investigate the nature of the processes occurring during the pyrolysis of PEEK,the investigations were carried out using gas chromatograph under isothermal conditions.It was concluded that during thermal degradation,the decomposition of the polymer starts with the rupture of ketone and ether bonds and proceeds to destruction of the benzene ring at higher temperatures,which is accompanied by the formation of H2O and CH4.Above 500℃,the polymer degradation further involved thermohydrolysis.The thermo-oxidation of PEEK,which was accompanied mainly by the formation ofH2,was noticeable beginning at 325℃.The total yield of the latter indicated oxidation of fragments of the benzene ring.