Ivan Ostrovský

Gas chromatography analysis of benzene, toluene, ethylbenzene and xylenes using newly designed needle trap device in aqueous samples

A newly designed needle trap device with Carbopack X as a sorbent material is used for sampling, preconcentration and injection of volatile analytes benzene, toluene, ethylbenzene and xylenes (BTEX) into gas chromatograph. The closed system of stripping the analytes from water samples was used. An injection port with a modified metal liner was used to desorb analytes trapped in needle trap device. The main advantage of needle trap device consists in the simple methodology and easiness and rapidity of the analysis. Needle trap device is suitable for sampling in field. The experimental parameters as breakthrough volume of stripping gas, linearity, repeatability and limit of detection (LOD) and quantification (LOQ) were investigated. LOD ranges from 0.05 to 0.07 microgL(-1) and relative standard deviation ranges from 0.5% to 11.6% at concentrations 5 and 0.1 microgL(-1), respectively.

Hochleistungs-gaschromatograpahie an flüssigkristallglaskapillaren☆

Abstract High-performance glass capillary columns with 5- n -heptyl-2-(4- n -nonyloxyphenyl)-pyrimidine were applied for separations of isomeric alkylbenzenes and n -alkens in smectic C and smectic A also in the nematic, isotropic and crystalline range. Structure-retentio correlations were discussed from calculated retention indices and their dependence on temperature. The smectic modifications shows better separations in comparison with previous methods.

Hochleistungs-Gaschromatographie an flüssigkristallglaskapillaren: I. Trennung von isomeren kohlenwasserstoffen an nematischen mesophasen

Abstract High-performance glass capillary columns with 4- n -pentyl-acetophenone (O-4- n -octyloxybenzoyloxime) were applied for separations of isomeric alkylbenzenes and n -alkenes in the nematic liquid-crystalline also in the crystalline and isotropic range. From the calculated retention indices and their dependence on temperature structure-retention correlations were discussed. A specific selectivity of the liquid crystals for isomeric n -alkenes was found and also their influence on other effects ( e . g . hindrance of propyl effect, anomaly order of retention of trans -6- trans -5-dodecenes, alternation of the relative retention with C-number). Different orientation in the mesophase shows differences in selectivity. The applied liquid crystal capillaries permit better separation of isomers in shorter time.

Capillary gas chromatography of linear alkenes on squalane

Abstract All positional and spatial isomers of straight-chain C 15 and C 16 alkenes (except both pairs of trans -5- and cis -4-isomers) were separated on an efficient squalane capillary column at 130°. The identification of the isomers was achieved with sufficient certainty only by means of gas chromatography. Retention data are given and unknown boiling points were derived from them.

Hochleistungs-gaschromatographie an flüssigkristallglaskapillaren : VII. Einfluss der struktur mesogener stationärer phasen auf die selektivität und auf die trennung isomerer C15C17-n-alkene

Abstract High-resolution gas chromatography with liquid crystal glass capillaries. VII. Influence of structure of mesogenic stationary phases on selectivity and on separation of isomeric C 15 C 17 - n -alkenes Relations between chemical constitution of symmetrical and unsymmetrical azoxy compounds as mesogenic stationary phases and selectivity for isomeric hydrocarbons were investigated. Influence of terminal groups and planarity of the liquid crystal molecule was found. Measurements on high-performance glass capillaries coated with 4-methoxy-4′-ethoxyazoxybenzene permit rapid and better separations of isomeric C 15 C 17 - n -alkenes.

Hochleistungs-Gaschromatographie and Flüssigkristall-Glaskapillaren : V. Trennung von isomeren n-Tridecenen und n-Tetradecenen

Abstract The separation of isomeric n-tridecenes and tetradecenes was investigated on high-performance glass capillaries with nematic 4-n-pentyl-acetophenone (O-4-n-pentyloxybenzoyloxime). The reproducibility of retention indices of n-alkenes in contrast to alkylbenzenes show only a small dependence on the film thichness of stationary phase. The influence of the effect of alternation on the resolution of neighboring positional isomers could be confirmed.

High-resolution gas chromatography with liquid crystal glass capillaries : IX. Separation of isomeric C9–C11n-alkenes and n-alkanes

Abstract The separation of isomeric C 9 –C 11 n -alkenes and n -alkanes was studied on high-efficiency glass capillary columns coated with nematic 4- n -pentylacetophenone (O-4- n -pentyloxybenzoyl oxime) (PBO) stationary phase. The separation was optimized with respect to the stationary phase film thickness, column temperature and carrier gas flow-rate. The use of PBO liquid crystal as the stationary phase makes it possible to prepare high-efficiency, stable glass capillary columns with improved properties in terms of resolution and speed of separation.

Hochleistungs-gaschromatographie an flüssigkristall-glaskapillaren : IV. Einfluss der alternation auf die trennung von isomeren kohlenwasserstoffen

Abstract High-resolution gas chromatography on liquid cyrstal glass capillaries. IV. Influence of alternation on the separation of isomeric hydrocarbons The influence of the effect of alternation on separation of isomeric n- alkenes C10–C15 was investigated on nematic, smectic and cholesteric mesophases. The results were compared with solution behaviour on common stationary phases. It was found that, as a result of the effect of alternation on liquid crystals, trans isomers with an odd number of carbon atoms and the double bond between an odd number of carbon chains and cis isomers with an odd number of carbon atoms and the double bond between an even number of carbon chains have a higher retention.

Shape selectivity of stationary phases for the separation of isomeric hydrocarbons by capillary gas chromatography

Abstract The selectivity coefficients and retention ranges of isomeric hydrocarbons on various stationary phases were compared. The advantage of liquid crystals, used as shape-selective stationary phases in capillary gas chromatography for the separation of structural and geometric isomers and diastereoisomers by hydrocarbons, is demonstrated.

Propyl effect and retention—structure correlation as a means of gas chromatographic identification

Abstract The influence of the propyl effect, i.e. , the intramolecular interaction between a propyl group and a π-electron system of a solute, on retention—structure correlations based on Kovats retention indices, is demonstrated. Its contribution is −1 to −5 index units for hydrocarbons analyzed on squalane and −4 to −10 units for structures with a double propyl effect. A more precise formulation of this effect and its quantification permit the explanation of deviations from regular structure—retention dependences and thus also the identification of the corresponding substances by gas chromatography, e.g. , 15% of 192 n -dienes up to C 11 exhibit the propyl effect.