5. It's a little wooly
Choice of liner type and packing material is important to ensure good injection reproducibility. There are several aspects which need to be considered.
Glass wool packing – deactivated glass wool is used to provide a large surface area from which less volatile components may volatilize, it provides a tortuous route through the liner so that the sample vapor is properly mixed to ensure good homogeneity, and also serves to wipe the tip of the syringe to avoid the discrimination processes whereby higher boiling analytes are selectively removed from the inlet prior to them volatilizing. For all these reasons, deactivated glass wool in the right amount, density, and positioning within the inlet liner can vastly improve the precision and accuracy of sample introduction, especially in splitless injection. If you are unsure of the right amount or positioning of the glass wool please contact your manufacturer.
Liner features – a gooseneck restriction at the bottom of the liner prevents analytes encountering hot metal surfaces and potentially degrading, which is especially useful in splitless injection. A gooseneck at the top of the liner prevents overfilling of the liner (backflash) and may improve analytical reproducibility.
For split injection, the default choice is a straight through (no gooseneck) unpacked liner. For splitless injection the default choice is a packed liner with a lower gooseneck.
For more information on liner selection see the following CHROMacademy page: GC Inlet Systems »
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