B. V. Stolyarov

Needle-type concentrator and its application to the determination of pollutants

A new method for impurity concentration in gas and liquid media using a needle type microconcentrator was developed. The main advantage of this method using microconcentrators is its efficiency and simplicity. Our work was stimulated by Pawliszyns solid-phase microconcentration method.

Headspace gas chromatographic determination of aromatic hydrocarbons in natural and waste water

SummaryThe possibilities of using headspace analysis of aromatic hydrocarbon traces in aqueous solutions with changing values of the partition coefficients are discussed. A variant of headspace analysis of the simplest aromatic hydrocarbon in natural and waste water is described. It involves two-step gaseous extraction of a sample in vessels of varying volume before and after the equilibrium phase is replaced with a pure gas (air or nitrogen). This method permits to analyse 5–50 ml water samples with benzene and toluene contents varying from the ppb to the ppm range within an error not exceeding 155. The analysis time is about 1.5 h. The presence of non-volatile organic or mineral substances does not influence the determination. This method is unsuitable to heterogeneous systems (aqueous oil emulsions): before carrying out the analysis for the hydrocarbon content these systems have to be homogenized first.

Homogeneous catalysis studied by reversed-flow gas chromatography

Abstract The reversed-flow gas chromatography technique was used to study the kinetics of dehydration of 2-butanol in phosphoric acid solution. A combination of the mathematical analysis developed in heteregeneous catalysis, mass transfer across gas—liquid boundaries, and diffusion of gases in liquids was employed to find the relevant equations pertaining to the present problem of homogeneous catalysis in a liquid phase. The equation describing the diffusion band of the reaction product(s) was derived for both a stirred solution and a quiescent one. These equations were then used to analyze the experimental data, from which the rate constants for the first-order reaction and for transporting the products away from the solution were determined. From the latter rate constant, the overall mass transfer coefficient of butenes in the liquid phase was found. This increases with temperature, showing that mass transfer coefficient of butenes in the liquid phase was found. This increases with temperature, showing that mass transfer across the gas—liquid boundary is activated, with an activation energy of 60.9 kJ mol−1. The diffusion coefficient of butenes in the reaction mixture, and their partition coefficient between the gas and the liquid phase, were also determined. The activation energy of the first-order reaction was found to be equal to 34.1 kJ mol−1.

A modification of the internal normalization method with sample splitting

SummaryThe procedure of sending a part of the sample vapor directly to the detector has been proposed earlier. This permits the quantitative determination of any sample component by relating its peak area to that of the total peak. This method represents a modification of the internal normalization method, with sample splitting. The necessary operating conditions and the applicability range of the method are considered. The dependence of the analytical results on the errors of splitting detector response factors and peak area measurements is discussed. Different types of split systems and flow paths have been tested. The possibilities of this method are demonstrated by determining the total amount of paraffins and cycloparaffins in platforming gasolines enriched in aromatics.

Reaction gas chromatography of alkyl halogenides. Optimization of the conversion into alkyl azides

SummaryThe central orthogonal composite design methodology is employed to find optimum conditions for the conversion of alkyl halogenides into alkyl azides in a chromatographic system. In spite of the difference in the chemical structure of the starting alkyl halogenides, we have found that there is a similarity in the effect of various factors on the conversion process of alkyl halogenides into the corresponding azides. Conditions have been established which provide 100% conversion of n-butyland isopropyl iodide. Computation of the response functions by the corresponding regression equations permitted us to define a region of optimum conditions common for the primary and secondary propyl- and n-butyl iodides and bromides, as well as for n-pentyl iodide providing for a conversion at least 90–95%. Differences in the relative retention times of the alkyl halogenides and the corresponding azides are sufficient to carry out identification by the peak shift method.