O. V. Rodinkov

Dissolved oxygen removal from aqueous media by the chromatomembrane method

The possibilities of the new chromatomembrane method in the removal of oxygen dissolved in water are studied. The scheme of the water deoxygenation process is determined. The new reagent-free method allows production of water with oxygen content at the level of a few ppb.

The properties of chromatomembrane cells in flow systems coupled to gas chromatography-analysis of volatile organic compounds.

The economical use of modern analytical instrumentation requires an online-coupling of efficiently working flow-systems which automate both sampling and sample pretreatment. Whenever extraction and preconcentration procedures are necessary the application of chromatomembrane cells proved to be very worthwhile. On this occasion the analyte exchange takes place inside a block of biporous PTFE wherein the two immiscible phases come into contact with each other. A special enclosure enables water and the extracting nitrogen to flow independently through that block. In case of gaseous extractants the behavior of the biporous PTFE and its mechanical parameter have to be investigated precisely in order to overcome the special problems of trace analysis in gases. The gas-chromatographic detection of volatile organic compounds (VOCs) requires a discussion on the effects of gas-sorption and the kinetics of equilibration which should be taken into consideration for using the chromatomembrane cell as an extractor from waste water. The investigation realizes at least that a quick pretreatment is made possible and, however, sample sizes decrease remarkably in comparison with competing methods as head space analysis or purge and trap technique. The application of chromatomembrane cells permits reasonable accuracies with a limit of detection on the ng/l level.

Surface-layer composite sorbents for the rapid preconcentration of volatile organic substances from aqueous solutions and gas atmospheres

The regularities of the dynamic sorption of volatile organic substances from aqueous solutions and atmospheric air on surface-layer composite sorbents, in which a finely dispersed sorption-active material is retained due to adhesion on the surface of a relatively coarsely dispersed macroporous carrier, were determined. The analytical capabilities of such sorbents were studied, and they were found more effective than traditional porous bulk sorbents used for the concentration of volatile organic compounds from aqueous solutions and gas atmospheres.

Chromatomembrane gas extraction generation of standard gas mixtures using composite carbon-fluoroplastic matrices

A procedure is proposed for the generation of standard gas mixtures of volatile organic substances based on chromatomembrane gas extraction with the use of composite carbon-fluoroplastic matrices. The regularities of this process were found, and an adequate physicochemical model was developed. The advantages of the proposed procedure over traditional bubbling and chromatomembrane gas extraction on unmodified matrices were demonstrated.

Liquid-gas adsorption chromatography

The history of the discovery, physical and chemical properties, and analytical potentialities of chromatographic methods using the stationary gas phase, such as liquid–gas and liquid–gas adsorption chromatography, are considered. Taking into account the retention of the stationary gas phase in the pores of a hydrophobic support, one can optimize the conditions for the separation and extraction of volatile substances from aqueous solutions on hydrophobic adsorbents in solid-phase extraction and reversed-phase liquid chromatography. “Scientific progress is the progress of a method.” M.S. Tswett

Chromatomembrane Preconcentration of Trace Impurities of Organic Pollutants from Natural Waters and Atmospheric Air

Physicochemical regularities and analytical potentialities of chromatomembrane gas extraction and chromatomembrane absorption as sample-preparation methods in determining organic pollutants in natural waters and atmospheric air were considered. The design of manifolds was described and the parameters of procedures involving chromatomembrane preconcentration of test analytes were presented.

Modification of hydrophobic sorbents by cobalt chloride in order to concentrate low molecular polar organic substances from the air for subsequent gas chromatographic determination

The article presents a new method of modification of hydrophobic sorbents. To improve sorption pre-concentration of polar organic compounds in the air analysis, these sorbents are coated with cobalt chloride. This modification increases retention volume of lower alcohols by 5-10 fold as compared to that of unmodified sorbents and solves the problem of gas-chromatographic determination at 1-2 ppb (micrograms/m(3)) by using the most common flame ionization detector. It should be noted that the modification of hydrophobic sorbents by cobalt chloride has little influence on their porosimetry parameters (specific surface area, proportions of meso- and micropores) and modified sorbents are capable of retaining hydrophobic nonpolar and weakly polar analytes as well as original unmodified sorbents. Thus, a fairly simple procedure leads to a large positive effect.

Compositional surface-layered sorbents for pre-concentration of organic substances in the air analysis.

We juxtapose methods of synthesis of non-polar surface-layered sorbents on the platform of a carrier, which combines macro-porous coarse-dispersed polytetrafluoroethylene with micro-dispersed activated carbon. Further, we present data about the sorption properties of the said materials alongside perspectives of their analytical applications. Our study established that with respect to efficacy of dynamic sorption from gaseous phases these sorbents outperform bulk-porous analogues in their normal, granular form.

Composite carbon-fluoroplastic surface-layer sorbents for the rapid preconcentration of organic substances from aqueous solutions

The regularities of the dynamic solid-phase extraction of organic substances (exemplified by chloroform, butyl acetate, and diethyl ether) from aqueous solutions on composite surface-layer sorbents, in which a finely dispersed sorption-active carbon material (active carbon or nanocarbon) was supported onto the surface of porous polytetrafluoroethylene, were found. It was demonstrated that the efficiency of the sorbents developed was higher than that of traditional bulk porous sorbents used for the preconcentration of volatile organic substances from aqueous solutions.

Gas-Chromatographic Determination of Gaseous Hydrocarbons in Aqueous Solutions Using Chromatomembrane Gas Extraction

A procedure was developed for the gas-chromatographic determination of gaseous hydrocarbons (C1–C4) in aqueous solutions using the continuous chromatomembrane gas extraction of test substances from a flow of the test solution. The procedure provides the rapid determination of background concentrations of methane in natural waters (0.1–1.0 μg/L).