A. V. Kudryavtsev

Quantitative and qualitative precision improvements by effective mobility-scale data transformation in capillary electrophoresis analysis.

By transforming the time‐based x‐axis of electropherograms in capillary zone electrophoresis (CZE) into the corresponding effective mobility‐scale, we propose a simple and robust data representation for a better qualitative and quantitative capillary electrophoresis (CE) analysis. The time scale of the raw electrophoretic data (detection signal versus time) is transformed into an effective electrophoretic mobility scale (μeff‐scale) with account of the electroosmotic flow (EOF) peak or of an internal standard of known effective mobility. With the new scaling (detection signals versus effective mobility), the obtained electropherograms are more representative of the velocity‐based electrophoretic separation and the comparison of complete electropherograms is directly possible. This is of importance when tracking peaks in real samples where alteration in EOF stability can occur or when comparing electrophoretic runs from different experimental setups (independence in column length and voltage). Beside the qualitative possibilities, a quantitative improvement is achieved in the μeff‐scale with significant better peak area reproducibility and equal to more precision in quantitative analysis than with the primary time‐scale integration.*

Size-exclusion chromatographic descriptors of humic substances.

An approach to the generation of size exclusion chromatographic (SEC) descriptors of humic substances (HS) is proposed. It implies a calculation of initial, central and normalised statistical moments and some of their ratios from the raw SEC-data. The proposed descriptors extend the pool of common molecular weight (MW) characteristics (average MW’s and their ratios) up to 20 parameters, which is important for the purposes of classification and prognostic modelling. Original software was developed to facilitate the computation of molecular weight distribution (MWD) and SEC-descriptors of HS from raw chromatographic data. The developed approach was applied to two model compounds and three humic materials. The discriminatory power of the calculated descriptors was roughly estimated on the example of three humic materials of different origin with the use of a multivariate variance analysis. Weight average MW and a ratio of the z- to weight average distribution coefficients were found to be the best discriminators, whereas the significance level of discrimination provided by the second moment and Mz/Mw-ratio was lower than 95%. ©2000 Elsevier Science B.V. All rights reserved.

Structure of Humic Acids in Zonal Soils from 13 C NMR Data

The structure of humic acids (HAs) in zonal soil types—soddy-podzolic soils (two samples), gray forest soil (one sample), and chernozems (two samples)—was quantitatively studied by 13C NMR spectros-copy. In the series considered, the content of unsubstituted carbon in the aromatic fragments of HAs increased, and the fraction of unsubstituted aliphatic structures decreased. HAs of soddy-podzolic soils were found to be enriched with carbohydrate fragments compared to HAs of chernozems and gray forest soil. The carbon skeleton of HAs from typical rich chernozem contained significantly more aliphatic and carbohydrate fragments compared to typical chernozem, which probably reflected the lower degree of HA transformation in rich chernozem.

A new technique for tritium labeling of humic substances

Abstract Humic substances (HS) of different origins have been labeled with tritium by the thermal activation method. Specific radioactivity of labeled HS ( 3H-HS) was sufficiently high and varied from 0.14 to 0.6 TBq/g. Parent HS and 3H-HS were analyzed by size exclusion chromatography with radioactivity and UV detection. The results allowed concluding that (1) neither partial decomposition nor polymerization of HS occurred during labeling and (2) tritium labeled molecules have a regular distribution among HS fractions of different molecular weights. The performed correlation analysis revealed that there was no significant relationship between HS properties and specific radioactivity of the obtained 3H-HS. Thus universality of the developed technique for radioactive labeling of HS with tritium could be demonstrated.

A comparative study of molecular weight distribution of water-soluble humic substances, humic acids, and fulvic acids extracted from sod-podzolic soils

The alteration of organic matter from three sod-podzolic soils in the course of the extraction of water-soluble humic substances was studied by means of size-exclusion chromatography using a combined UV-DOC detector. A comparison of water-soluble humic substances with humic and fulvic acids extracted from the same soils was carried out.

On the Bayesian approach to the analysis of queueing systems and reliability characteristics

The paper discusses the statements or problems and the results obtained by the authors since 2005 within the bounds of application of Bayesian approach to some problems of queueing theory and reliability theory, as well as some directions of further research in this area. The method provides the randomization of system characteristics with regard of a priori distributions of input parameters. This approach could be used, for instance, for calculating moment and quantile characterics for performance and reliability characteristics of large groups of systems or devices.

Tritium labeling: A unique tool for studying the behavior of humic substances in living systems

A range of labeled humic substances was obtained by the tritium thermal activation method. The high specific radioactivity and radiochemical purity allowed direct determination of the hydrophobicity and surface activity of humic substances, and investigation of the behavior of humic substances in bacteria and plants.

Molecular Composition Study of Mumijo from Different Geographic Areas Using Size-Exclusion Chromatography, NMR Spectroscopy, and High-Resolution Mass Spectrometry

Four mumijo samples originated from different mountain ranges were studied using size-exclusion chromatography (SEC), Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS), and 1H and 13C NMR spectroscopy. All the used analytical techniques demonstrated that the mumijo samples studied consist of a “high-molecular” fulvic-like and a low-molecular components. The second component is shown using FTICR MS and NMR methods to be predominantly a range of vegetative and animal metabolites.