Slow GC response

[patcontr]

Hi, I am new with GCs, but I been working lately in a Shimadzu GC 2014, with TCD. My problem now is that takes at least 30 minutes for the GC to be ready, even though all the temperatures and flows are already at the setting temperature.
My other problem is I have a misterious peak at the beggining of any sample, even a blank one.
Can anyone give me any advice?

[DR]

Check that your default temperatures are a match for the starting temperatures in your method of choice. It sounds like you're waiting for a late change in temp. Also, check for leaks. They are the cause of most aberrant early behavior.

If you want more specific information, you will have to provide a lot more detail about your column, injection size and timing as well as temperatures...

[chromatographer1]

My guess is your 'mystery' peak is caused by the change in pressure caused by an injection which also causes a change in flow, a flow/pressure pulse, which when reaching the detector changes the conductivity of the carrier gas in relation to that of the reference side of the TCD.

It is a common phenomenon, especially if you are using a syringe larger than several microliters in volume.

See for yourself: inject 0 µL (insert the needle empty) then increase the volume of 'air' or fill the syringe with carrier gas and make more injections with larger and larger amounts of gas. You can also use liquid samples of solvent.

best wishes,

Rodney George
consultant