Günter Kraus

Analysis of heavy metals and sulphur-rich compounds in the water moss Fontinalis antipyretica L. ex Hedw.

The water moss Fontinalis antipyretica has been investigated to estimate heavy metal pollution in the river Elbe (middle Germany). Procedures of plant separation, digestion as well as an analytical method for ICP-MS analyses have been evaluated. Reproducibility and accuracy have been demonstrated on BCR 61 (NIST) reference material and results have been compared with AAS and AES data. The distribution of heavy metals in different plant segments of indigenous material has been analyzed. Exposition of plant material in the river Elbe have shown no correlation between the heavy metal content in plants and that of water samples. Cd and Zn concentrations found in the plant material are significantly enriched relatively to control samples. To understand the sophisticated ‘real system’ experiments have been carried out under laboratory conditions to investigate induced sulphur-rich compounds in the presence of heavy metals using HPLC including on-line derivatization.

Löseverhalten kristallin-flüssiger phasen in der kapillar-gaschromatographie : I. Lösseigenschaften nematischer oximester

Abstract Solution behaviour of liquid crystal phases in capillary gas chromatography. I. Solution properties of nematic oxime esters The use of capillary columns to investigate the solution properties of a homologous series of liquid-crystalline-4-n-pentyl-acetophenone-(O-4-n-alkoxybenzoyloximes) was very favourable. A number of disubstituted isomeric benzenes could be completely separated in columns of a length of only 8 to 27 m. The alternations of partial molarenthalpies and entropies of solution were discussed in terms of the Maier-Saupe theory. The p-isomers show in the nematic ranges in most cases the largest partial molar enthalpies of solution and the smallest solute activity coefficients. Because of the shape, the polarizability and polarity, the p-isomers have the largest translational energy loss in comparisons with o- and m-isomers

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.

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.

Highly selective liquid crystalline polysiloxane stationary phase for gas chromatographic separation of isomers

Abstract The gas chromatographic isomeric selectivity (for p- and m-xylene) of six mesogenic monomers and polysiloxanes having various side-chains, degrees of polymerization and linking ester groups (- OOC- and -COO-) were investigated. The results indicate that the polymeric stationary phases had higher isomeric selectivities. The highest selectivity coefficient for p- and m-xylene, α =1.21, was obtained at 65°C for the polymeric stationary phase [4-octyloxy(4-allyloxyphenyl benzoate)] polymethylhydrogensiloxane (POBAP-20) with an optimized film thickness of 0.63 μm.

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.

Löseverhalten kristallin-flüssiger phasen in der kapillargaschromatographie: II. Löseeigenschaften smektischer A-, B- und C-modifikationen

Zusammenfassung The solution behaviour of smectic A-, B- and C-modifications has been investigated by capillary gas chromatography. When the crystalline liquid order of the phases smectic B, C and A decreases the solubilities increase. At the transition temperatures the partial molar free excess enthalpy differences can be correlated to the heats of transition. The thermodynamic data determined by gas chromatography confirm the system of thermotropic liquid crystal phases.

Hochleistungs-gaschromatographie an flüssigkristallglaskapillaren : III. Trennung von isomeren kohlenwassertstoffen an cholesterinischer mesophase

Abstract High-resolution gas chromatography with liquid crystal glass capillaries. III. Separation of hydrocarbon isomers on cholesteric mesophase high-performance glass capillary columns with cholesteryl butyrate as stationary phase were applied for separations of isomeric alkylbenzenes and n -alkenes in cholesteric, crystalline, isotropic and supercooled range. Structure-retention correlations, retention indices, d I /d T values and homomorphy factors are discussed. The cholesteric modification shows a higher selectivity for trans - cis -isomeric n -alkenes, than nematic and smectic mesophases or common stationary phases.