Liner choice

Discussions about GC and other "gas phase" separation techniques.

9 posts Page 1 of 1
Hello,
Could you recommend a good liner for ethanol measurement?
We produce pure ethanol from corn,(99.8%) I measure it with Gc Shimadzu 2010 plus with FID.
My problem is acetaldehyde,because it’s very volatile, it depends on liner geometry.I’ve tried many variations of liners(shimadzu,agilent) .The best was splitless liner which I have filled with glasswool,but it’s difficult to fill it ,and the value of acetaldehyde could hardly be reproduced.
Thanks a lot.
I am assuming you are using headspace sampling. You do not need wool and you do not need a large volume liner as the sample is already in a gaseous state it is not vaporizing and expanding in the inlet. Consequently you want a narrow liner to keep the sample focused. I use a 1mm ID Restek 20973.

Using a split liner with wool only adds room for band broadening and the wool needlessly adds active sites.
Thanks for your answer.
I will try to find a similar liner for my Shimadzu GC which you recommended.(I need 95 mm long)
Many thanks:)
Aniko74 wrote:
Thanks for your answer.
I will try to find a similar liner for my Shimadzu GC which you recommended.(I need 95 mm long)
Many thanks:)


Look for one made for SPME (Solid phase micro extraction) Those are typically 1mm or less ID.
The past is there to guide us into the future, not to dwell in.
Unfortunately,I don’t use headspace,(we don’t have)do you thing it will be good for me?I have tried one straight type liner(2,6mm i.d)this week,without wool,but aldehyde has dissapeared from the sample...
How are you preparing and injecting the samples if not headspace? There really isn't any good alternative to measuring acetaldehyde and ethanol rather than headspace.

If you are doing direct injection of water or methanol extract your GC will get fouled up very fast and acetaldehyde is very active and disappear in a fouled liner and column. I saw one old paper that used a liner with glass beads that got changed out every 50 samples or so. However, this analysis really needs headspace sampling anything else is kind of a hack.
Our gc has an autosampler which inject 1microliter ethanol sample ,I use split injection (split ratio 40)Injector temperature is 220 C Column is a restek 1701,30 m long.Sample is very pure,99,8% etanol,apr. 500 ppm acetaldehyde in it.
I see so you are basically checking for acetaldehyde in an fairly pure ethanol sample. Headspace would still be preferable. Also keep in mind acetaldehyde tends to form paraaldehyde and aldehydes also react with alcohols to for acetals.

In this case use a large volume liner with wool in the middle and a bump at the bottom for the split flow. You also want to make sure everything is fairly well deactivated. Also make sure you are using a gas-tight injector syringe.
Thanks your advice!
I’m trying to use an agilent inert liner(3.4 mm I.D)with wool,aldehyde results ok,as you have mentioned ,acetal value was too high,so I changed the oven heating up temperature,now I see normal acetal data.
Many thanks :P
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