Optimization of selectivity by tuning column temperatures for series-coupled capillary columns in dual-oven gas chromatographic systems

A method has been developed and evaluated for optimization of the selectivity of series-coupled capillary columns in a twin-oven gas chromatographic system in the shortest possible analysis time. The temperatures of either one or both columns were varied independently (partial optimization) or simultaneously (overall optimization), in order to separate the maximum number of sample components. The method is based upon computer-aided calculation of Kováts indices of the coupled columns by means of second and third order (polynomial) functions of the temperatures of the individual columns. The applicability and limitations of the methods are discussed and illustrated with separations of a synthetic hydrocarbon mixture of 33 components

The use of solid sorbents for direct accumulation of organic compounds from water matrices : a review of solid-phase extraction techniques

The main principles of solid-phase extraction techniques are reviewed in this paper. Various solid sorbents can be used as a suitable trap for direct accumulation of organic compounds from aqueous solutions. The trapped analytes can be desorbed by elution with suitably chosen liquid phases. These preconcentration procedures can be considered as low performance liquid chromatography and the efficiency of the procedure can thus be related to the retention characteristics of the preconcentration column. The main sorbents used for trace enrichment purposes are also reviewed. Besides, the concise methodology, sample storage, and automation are discussed. The advantages of solid phase extraction as compared to liquid-liquid extraction are given as well as some drawbacks of this method

Correlations between boiling points and relative retention data for hydrocarbons

An equation correlating retention indices, boiling points and activity coefficients is proposed. The equation can be applied not only to homologous series, but also to different classes of hydrocarbons

Analysis of divalent metal dialkyldithiocarbamates by gas chromatography and mass spectrometry

The influence of various gas chromatographic supports, coated with SE-30 as stationary phase, on the qualitative and quantitative analysis of Ni(II) and Zn(II) dithiocarbamates was investigated. Retention indices were correlated with the structures of the compounds studied. Cu(II), Co(II) and Cd(II) dialkyldithiocarbamates decomposed during analysis under the applied conditions. Special emphasis was given to the quantitative analysis of Ni(II) and Zn(II) bis(N,N-dialkyldithiocarbamates). Basic conditions were established for the separation of Ni(II) bis(N,N-dialkyldithiocarbamates) on glass capillary columns coated with polydimethylsiloxane stationary phases (OV-101 and SE-30). The main problem in the successful analysis of these compounds in glass capillary columns was found to be adsorption on the column wall. Electron-impact positive-ion mass spectra of Ni(II) and Zn(II) bis(N,N-dialkyldithiocarbamates) are discussed in detail. From the mass spectra of these compounds, general fragmentation pathways were derived. All of the dithiocarbamates studied showed molecular ions, the intensity of which decreased with increasing size of the alkyl substituent