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Comprehensive two-dimensional gas chromatography (GC x GC) offers significant improvement for volatile chemical separation. Selecting suitable first (¹D) and second dimension (²D) columns normally requires consideration of the chemical composition of a sample. Replacing one of these dimensions with a two-column ensemble (for example, ¹D1 + ¹D2 for the ¹D column), provided with a pressure tuning makeup gas between them, varies the relative retentions of compounds before the modulation step according to the junction pressure. This makes it possible to alter the apparent polarity of the ¹D ensemble, and this alters peak positions in the 2D GC x GC space. This article presents an account of studies that suggest this offers potential for improved operation for a GC x GC laboratory. [ABSTRACT FROM AUTHOR]

Abstract: In a recent contribution a design method for steady-state recycling chromatography in the so-called mixed-recycle mode (MR-SSR) has been proposed by . The method holds under ideal, dispersion-free conditions for chromatographic systems with competitive Langmuir adsorption isotherms. Here this approach is extended to practically relevant nonideal conditions with significant dispersive effects and convex-upward adsorption isotherms in general. The developed shortcut design method allows designing MR-SSR processes based on a simple procedure applied to a single conventional chromatogram. The method is validated experimentally for the separation of two cycloketones on a polymeric stationary phase. The performance of the MR-SSR process is compared to batch chromatography by means of a simulation study. [Copyright &y& Elsevier]

The article examines several activities of some leading separation science research institutes in Austria. One group is the Institute Chemistry and Radiochemistry which simplifies sample preparation technique to isolate trace components from complex environmental to allow interference-free chromatographic measurements. Other groups include the Institute of Analytical Chemistry, Institute of Chemistry-Analytical Chemistry, and Center for Analytical Chemistry.

Discusses calibration in chromatography. Importance of residual standard deviation in estimating the prediction interval and uncertainty of the result; Determination of the standard deviation of a signal at its lowest and highest concentration.

Part II. Investigates the baseline disturbances in chromatographic systems with refractive index detection using acetonitrile-water mixtures on amino-phase columns. Role of minor fluctuations in the column thermostat in causing composition fluctuations in the column effluent; Correlation between the magnitude of these composition fluctuations and the time derivative of the temperature fluctuations.

The article explores a problem related to the transfer of a method from one instrument to another in chromatographic analysis. It discusses how to troubleshoot this liquid chromatography (LC) problem. It suggests that a periodic system performance qualification test be performed for each LC system on a semiannual or annual basis so that method transfer problems will not occur.

Discusses the extracolumn effects on the chromatogram's appearance. Advantages of checking for reasonable chromatographic behavior; Importance of controlling temperature and checking its influence on the separation; Retention factor for the analyte in the liquid chromatography assay.

The article focuses on the impact of the size of pore packing materials for peptide separations in ultra performance liquid chromatography peptide mapping. The pore size materials of 130 A and 300 A are compared in the separation of its two complex peptide digests. The result shows that both peptide separation technology columns give useful separations of peptides over a wide range of sizes and chemical properties.

Features several literature on separation science. Dionex Corp.'s product catalogue on CD-ROM; Bionisis' application bulletin describing how scientists can monitor the metabolism of radioactively labelled drug candidates; Sun-Sri's catalogue for its range of chromatography vials and validated syringe filters.

The article presents information on multidimensional separations in analytical chemistry. Conventional, heart-cut multidimensional separations are valuable when extra resolution is needed in the examination of a small segment of peaks in a complex chromatogram. Prior knowledge of the sample composition is always beneficial. In comprehensive multidimensional separation techniques, the entire sample, not just a part of it, is subjected to different separations. Separation techniques that utilize more than two dimensions can certainly be expected in the future.

Lists conferences on separation science for February to June 2004. Eighth International Symposium on Hyphenated Techniques in Chromatography and Hyphenated Chromatographic Analyzers in Brudges, Belgium; Environmental Mass Spectrometry Meeting in Chester, England; 27th International Symposium on Capillary Chromatography in Italy.