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  • Title: Uncoated capillary column inlets (retention gaps) in gas chromatography.
    Author: Grob K, Schilling B.
    Journal: J Chromatogr; 1987 Mar 27; 391(1):3-18. PubMed ID: 3294873.
    Abstract:
    Uncoated but deactivated pre-columns have become a widely used tool in capillary gas chromatography (GC), serving strongly differing purposes. Pre-columns are often used as guard columns, reducing the effects of involatile sample by-products on chromatographic performance and rendering exchange of contaminated column inlets simple. Wide-bore pre-columns facilitate introduction of the syringe needle and open the way for a relatively robust on-column autosampler. Other pre-columns are used for re-concentrating solute bands that are broadened due to the flow of sample liquid in the column inlet (retention gap). Long pre-columns allow on-column injection of large sample volumes (e.g., 50-80 microliter when a 15 m X 0.32 mm I.D. pre-column is used). The background of the various uses of pre-columns is discussed, concluding with an evaluation of different deactivation methods for the internal wall of the pre-columns. Critical parameters are inertness, wettability and retention power. Press-fit connections are recommended for coupling pre-columns to the coated columns.
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