We often get asked in tech service which injection port liner we would recommend for a particular analysis. For this type of question, it would not be uncommon to receive different answers, as each person has had positive and negative experiences with different liner styles. As a result, the recommendations I provide below are based solely on my past experiences, and do not reflect those of the rest of the tech service group.
Because I used Agilent instruments with split/splitless injection ports for most of my career, I will only provide you the Restek liner catalog numbers designed for these instruments. If you are using another brand of GC, you should be able to determine if we have a similar liner for your particular instrument make/model. Just click on this link Inlet Liners & Liner Supplies and look for “Instrument Manufacturer/Model” under the “Narrow Your Results” filter.
When doing split/splitless, or splitless injections, I usually recommend a single gooseneck liner (no wool). I have experienced efficient sample transfer when the capillary column is installed around 5-7mm from the tip of the compact ferrule. Depending upon the expansion volume of the solvent (or the volume of a gas sample), either a 2mmID or 4mmID should be selected. Our Solvent Expansion Calculator can help you determine the proper liner internal diameter (ID).
The liner below is Restek 23302.1 Sky® 4.0mm ID Single Taper Inlet Liner , which is typically the best choice for 1-2µL injections of non-polar solvents (like hexane), 0.5-1µL injections of polar solvents (like methanol), and gas injections approximately >250µL.
The liner below is Restek 23315.1 Sky® 2.0mm ID Single Taper Inlet Liner , which is typically the best choice for 1µL or less injections of non-polar solvents (with low expansion volumes), or gas injections less than approximately 250µL.
Do I ever recommend a wool-packed split/splitless liner? Sure I do, but only when analyzing very dirty samples, when increased surface area is needed to properly vaporize the sample/compounds, or when doing water injections. However, I personally never recommend water injections be done in split/splitless or splitless mode. I have been able to obtain better peak shapes and peak area count reproducibility using split mode.
When doing split injections, I usually recommend a Cyclosplitter liner like Restek 23312.1 (photo below) Sky® 4.0mm ID Cyclo Inlet Liner . I have found that this style of liner does a great job of vaporizing a sample through increased internal surface area and by introducing turbulence to the sample.
There is, however, one drawback with these liners; they are very difficult to clean. Therefore, if you have dirty samples, or those containing non-volatile residue, I would probably suggest 23300.1 instead (photo below) Sky® 4.0mm ID Straight Inlet Liner w/ Wool
If you are not using a syringe for sample introduction, but instead the sample is from a purge & trap unit or gas sampling valve, then the liner I usually recommend is 23333.1 (photo below). Sky® 1.0mm ID Straight Inlet Liner
There is one more liner that I think every lab should own, a Uniliner®. Although I usually don’t recommend this liner for any specific analysis, I think it’s a great troubleshooting tool because, when properly installed, it can help isolate & even eliminate injection port issues like activity. Just remember, these liners are designed for splitless injections only (if you experience carryover, try turning on the split flow at 5mL/min after the last compound elutes).
A Drilled Uniliner® with the “hole near top”, like Restek 23311.1, is typically the one I suggest (photo below). Sky® 4.0mm ID Drilled Uniliner® Inlet Liner with Hole near Top .
In summary, I believe every lab should have several, or all, of the liners I’ve listed above in their inventory. Will other liner styles provide even better analytical results than any of these liners? I think it would be safe to say “yes”, but only through trial and error would you know for sure. My suggestion, start with one of the liners listed above, and if the desired analytical results are not achieved, only then would I look for a different liner style. Thanks for reading.