Chromatography Forum

Dear All,
I'm analyzing with FID some VOC in solid samples dissolved in propanol wtih splitless mode.
I've installed a pre column (about 1 m for 0.53 ID of empty silica tube connected with universal glass press-fit) in front of 30 m 0.53 ID 1um HP-Innowax for inject dirty samples.
If I compare the areas of standard solutions injected with or without the pre column I can observe a difference of about 20% (with the precolumn I've 20% less than without); is it normal? Where is the problem?
Thanks

First guess would be a leak...

Sometimes if your column cut is not clean enough, you might have problems fitting it and leakage from there.

be aware that glass pressfits can have active places which can be responsible for loss of alcohols.
press-fits should be deactivated.
This can be done with DMDCS, procedures can be found in internet

You say that your pre-column is "empty silica tube", if this means that it is not deactivated then you are very probably losing analytes by adsorption to the pre-column. The pre-column has a much larger surface area than the press-fit.

If the pre-column has a non-polar deactivation the propanol solvent will not wet it and you will get peak distortions that might cuase a loss of integrated area.

You need to use a pre-colum with a polar deactivation.

Good luck Peter