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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]

When we made changes in the column conditions (length, diameter, particle size or flow rate) under isocratic conditions, the observed chromatograms matched our expectations. However, when we made the same changes in a gradient separation, sometimes the results were quite surprising. Isocratic lvalues (equation 2) are not influenced by changes in the column conditions, so peak spacing, a (equation 1) won't change, either. This is not the case with gradients, because k* is influenced by the flow rate and the column volume (equation 3), so when changes in these factors are made, a change in k* results, with a corresponding change in a. We found that if we made compensating adjustments, using equation 4 for a guide, we could change the column conditions for a gradient separation and get the expected result. The key learning point here is if changes in the column conditions are made for a gradient separation, compensating changes must be made to keep k* constant, or the separation is likely to undergo undesirable changes. [ABSTRACT FROM AUTHOR]

The article offers the author's insights on the comparison of gradient and isocratic separations under the same conditions. The author describes the equivalent conditions under which the peak and retention properties are almost the same with gradient and isocratic runs. He states that if the isocratic k-value is too large, it will be difficult to obtain a single isocratic separation in liquid chromatography (LC) without sacrificing run time and peak height.

The article presents a case study on the appearance of an extra peak in liquid chromatography (LC). It mentions the causes of the extra peak in isocratic or gradient separations such as late elution, a carryover from an earlier injection, and ghost peaks, which arise when the mobile phase is contaminated. It also discusses how to troubleshoot a chromatogram once the presence of an extra peak is detected such by replacing the suspected part or the column.

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.

Features several separation science equipment products. Chromatography software from Waters; Chromachem evaporative light-scattering detector from ESA; Twister high-speed evaporator from Presearch Ltd.

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.

Crude synthetic peptide samples were separated on preparative Atlantis™ dc18 columns. Fraction collection was triggered by the mass-to-charge (rn/z) ratio of the peptides. which specified the target peptide in the collected fraction to increase the fraction purities. Mass-directed peptide purification was more robust than UV-based collection under overloading conditions, and increased the traction purities. LC-MS-MS analysis was further employed to identify the impurities in the crude synthetic peptide sample. This study demonstrates high mass loading, selective purification. high recoveries and purity, and the capability of utilizing mass-directed fractionation for purifying peptides on preparative RPLC columns. [ABSTRACT FROM AUTHOR]

Provides information on the 17th International Symposium on Microscale Separations and Capillary Electrophoresis in Salzburg, Austria. Topics that will be discussed during the symposium; List of events and activities; Contact information.

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.

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.