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.     

Statistical analysis of some topochemical models

A model process is considered in order to investigate the applicability of a particular statistical approach to determination of an input mechanism of topochemical reactions and of the relevant mathematical model.It is shown that the analysis of the experimental data leads to different results due to the reproducibility errors. The applied statistical approach allows one to determine the input mechanism unambiguously when has the value of 0.01.

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Zusammenfassung Ein Modellverfahren wird zur Untersuchung der Anwendbarkeit einer bestimmten statistischen Näherung zur Bestimmung eines Inputmechanismus topochemischer Reaktionen und des einschlägigen mathematischen Modells herangezogen.Es wird gezeigt, daß infolge von Reproduzierbarkeitsfehlern die Analyse der Versuchsangaben zu verschiedenen Ergebnissen führt. Die angewandte statistische Annäherung gestattet die eindeutige Bestimmung des Inputmechanismus bei einem Sigma-Wert von 0.01.

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Résumé On considère un processus modèle pour vérifier s'il est possible d'appliquer une approximation statistique particulière pour déterminer le mécanisme initial des réactions topochimiques et le modèle mathématique respectif.On montre que l'analyse des données expérimentales conduit à des résultats différents en raison des erreurs de reproductibilité. L'application de cette approximation statistique permet de déterminer le mécanisme initial sans équivoque, pourvu que la valeur de soit égale à 0.01.

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- . , , . , 0,01.

     

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.