Chromatography Forum

Hi everyone from Texas.
I am a german Expat working here in Houston, setting up a new Lab.
Back home, I used Perkin Elmer GCs for almost 20 years, here I have to deal with Agilent / Chemstation.

Now, I have one Turbomatrix 40 HS connected to a 7890B GC. I want to operate it splitless. I am supposed to have an excess flow of about 30 ml/min from Headspace to GC Inlet.
Turning the Split off in the Method results in problems regarding the Carrier Gas Pressure being too high and the GC does not reach its READY state. If I turn off the Carrier Gas Pressure in the Method to use only the Carrier Gas coming from the HS I don't have any signal at all (I assume thats because unchecking the pressure shuts down the inlet completely).

What do I need to do to to go splitless?

Thanks
Frank

How is your HS connected to the gc?
If you indeed have 30cc/min from your HS, I think you will need to split.

The Transfer Line from the HS Unit is connected to the Inlet and the Pressure on the HS is about 25 psi. The Carrier pressure in the Method is 21 psi.
The 30 cc/min is the "over pressure" needed so my sample is getting on the column and not being pushed back to the HS.

I just don't understand ... if I go to splitless mode the Chemstation and GC Method settings are set to 20 psi pressure and it holds. If I initiate a PrepRun the purge valve opens and the pressure goes up to the Pressure set at the HS. How do I prevent that???

Sorry, what I meant was is the transfer line cut in to the as inlet line to the injection port, or ende in a needle through the septa?
If you put it in series with the injection port gas supply, the sample transfer will be controlled by the GC.

Hello baderfrank,

IMHO, it is best to avoid the GC inlet, as cold trapping of volatiles can occur.

I have had best results where the transfer line is connected directly into the oven.
You may be lucky and only have one GC Inlet, therefore the rear GC inlet hole can be
opened up, and the transfer line secured into there and protrude into the gc oven slightly
and then fastened in place.
I would then run the column directly into the TurboMatrix, avoiding having to have any connections
(noting that the manufacture usually recommends a pre-column with no stationary phase to avoid
column bleed, but my analytes were being affected by the joiner, and column bleed wasn’t a problem for me)

Thus the split/splitless and pressure is controlled via the TurboMatrix, and the GC inlet pressure and temperature are turned off.

Of course switching back to liquid injection is similarly going to be labour intensive,
unless you use a column joiner.

Kind regards
Alex