High-Sensitivity Determination of Hydrocarbon Impurities in Arsine by Reaction Gas Chromatography

It is shown that the results of determining methane in high-purity arsine by reaction gas chromatography can be overestimated by more than two orders of magnitude. This overestimation is caused by the formation of methane as a side product of the reaction. Cryogenic preconcentration at the injection stage is proposed to improve the accuracy of determination of methane, and the cryofocusing of impurity hydrocarbons is proposed to improve separation. Detection limits of (3–10) × 10^–6 vol % are achieved for C₁–C₅ hydrocarbons.     

Sorption-photometric and test determination of lead in environmental materials

The main analytical characteristics of the reaction of hexaoxacycloazochrom with lead were determined. A method for the sorption preconcentration of lead on the Thiopan 14 sorbent was proposed. Procedures were developed for the photometric determination of lead in natural waters, air, and soil at the level of the maximum permissible concentration. A new melange gel technique for preparing silicic acid xerogels modified with hexaoxacycloazochrom was developed for the test determination of lead in environmental samples at the level of the maximum permissible concentration.     

Fractionation and Determination of Different Lead Species in Contaminated Soils

A new approach was proposed to fractionating soil lead species differing in mobility and biological availability. Ground solid samples were retained as a stationary phase in a rotating coiled column while continuously pumping aqueous solutions of salts and complexing agents necessary for the sequential leaching of different element species. It was shown that field-flow fractionation in a rotating coiled column is suitable for separating three lead species in an automatic mode within 4 h, as compared to several days for conventional methods of sequential extraction. The study of lead elution curves at different fractionation steps provides additional information about its mobilization under changing environmental conditions.     

Synthesis, structure, and electrochemical properties of 12,42-dioxo-21,31-diphenyl-7,10,13-trioxa-1,4(3,1)-diquinoxalina-2(2,3),3(3,2)-diindolizinacyclopentadecaphane

The oxidative dehydrocyclization of the 3-(indolizin-2′-yl)-2-oxoquinoxaline monopodand performed either electrochemically or under the action of molecular iodine affords new redox-active heterocyclophane consisting of the redox-switchable biindolizine fragment combined with the polyether-bridged π-deficient quinoxaline systems. The single-crystal X-ray diffraction study showed that the trioxaundecane chain of heterocyclophane adopts an extended conformation, and one of the phenyl substituents of the molecule closes the pseudocavity formed by the spacer from one of the sides. The cyclic voltammetric study of heterocyclophane in MeCN and DMF showed the three-step oxidation of the indolizine fragments accompanied by the single-electron transfer in each step. The first and third steps are reversible, and the second step is irreversible. The oxidation at potentials of the first peak gives rise to stable radical cations detected by the ESR method (g = 2.0024, a _2N = 0.26 mT). Dedicated to Professor E. A. Berdnikov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1991–2003, October, 2007.     

Track membrane with immobilized colloid silver particles

A method for modification of track membranes by immobilization of polymer complexes of colloid silver nanoparticles on the surface of microfiltration membranes was developed. The antimicrobial properties of track membranes modified with silver nanoparticles were tested on E. coli, Ps. aeruginosa, St. aureus, and B. cereus.