Liner Design Features
Dimensions
- The outside diameter (OD) of the liner determines if the liner is more effectively used in split or splitless mode
- Larger OD liners are designed for splitless operation, fit tightly and limit sample contact with metal parts of the inlet
- Larger OD liners improve analyte recovery by retaining more sample inside the liner
- Agilent splitless liners are all designed with exacting dimensional tolerances to fit tightly in the inlet and minimize sample contact with metal surfaces
- Smaller OD liners are designed for split injection because they produce less resistance to carrier and split flow through the inlet
- Large volume liners are used for split injections with enforced dimensional stability for a wide range of split ratios
Tapers
Tapering or narrowing the liner internal diameter (ID) is done for a number of purposes:
- Bottom taper focuses sample onto the head of the column
- Bottom taper minimizes contact with metal parts of the inlet
- Center taper positions glass wool correctly
- Top taper minimizes sample backflash
To operate properly, the column must be installed correctly in the injection port with the tip of the column ideally located about halfway into the taper, or about 6 mm from the column tip to the top of the ferrule. Some applications work better with different column installation depths. Therefore, you should check the instrument manual for proper installation distances and determine which distance is appropriate for your application. Reproducible positioning is important for repeatable quantitative results.
Packing
Glass Wool
Many liner designs used deactivated glass wool packing. The glass wool is positioned or held in place near the center of the liner to:
- Provide additional surface area for complete volatilization of the sample to minimize thermal discrimination
- Trap non-volatile components and septum particles before they reach the column
- Wipe any sample from the syringe needle, thereby increasing reproducibility and preventing sample residue build-up at the septum or Merlin Microseal
Glass wool liners that have glass wool near the center of the liner, such as Agilent Part Nos. 5183-4647 and 5183-4711, are recommended for automatic injections or when using the Merlin Microseal septum.
If glass wool is positioned at the bottom of the liner, its main purpose is simply to trap non-volatile components. Glass wool is generally not recommended for the following analytes:
- phenols
- organic acids
- pesticides
- amines
- drugs of abuse
- reactive polar compounds
- thermally liable compounds
Glass Cups
Another design feature used to help volatilize the sample and provide good mixing is the incorporation of a glass cup inside the liner. Glass cup liners are also available with additional glass wool and inert packing to increase reproducibility and limit sample discrimination. Not recommended for use with Electronic Pressure Control Inlets.