Chromatography Forum

Hi

I'm about to buy inlets and septa. Using THF in my analysis i've chosen a silicone/PTFE septum and believe that should be perfect (for any analysis really).

However im about more in doubt with the inlet. I'm a bit set on focused liners with a tapering in the bottom. I see that focused liners are very popular and seemingly make more reproduceable results - so this sounds perfect. However i'm a bit in doubt on the tapering. Some sites say this is mainly for splitless injection whereas other (incl supplier) say split/splitless and the tapering is just guiding the gas towards the column.

Is a focused liner with tapering in the bottom a good choice for split 1:20 analysis of bio-oils solvatised in THF?

You can try some of each and see if either gives better results. I've tended to use the tapered liner for splitless and an open liner with wool for split - because it is my habit. Sometimes it makes a difference in the quality of the analysis - and sometimes it does not. If the selection of a liner will make a difference, it will be because of the analytes in the mixture you are analyzing.

I would strongly consider the tapered liner for your application to keep the inlet system cleaner. Bio-oils tend to leave some residue, and with the tapered liner less of this will end up on the bottom of the injection port.

My thought exactly - im going for the tapered ones then, thank you for your help

tapered or gooseneck liners are to be used for liquid injections. Straight-through liners for gaseous injections. The taper allows the liquid a bit more time to volatilize before it exits the bottom of the liner. Otherwise, one can get what is called the Leidenfrost effect, not a good thing when it comes to reproducibility/response.

You can use a liner with a glass wool plug in it to catch non-voalitle material. They come in both tapered and straight through styles. Wool can cause degredation - so folks who do pesticides tend to avoid it. When you are analyzing very dirty samples, however, the wool will collect nonboiling material and keep it off the head of the column. With a sufficient plug of wool, you do not need the taper to avoid liquid contact with the bottom of the inlet. However you can get a tapered liner with wool to avoid any remaining issues with the bottom of the liner.

Browsing the inlet liner portion of a chromatoraphic supply catalog will give you an overfies of kinds of liners and uses.