Chromatography Forum

Hello,

I would like to install a HP7694 Headspace on a 6890 GC with S/SL inlet and it's the first time i will use an headspace. So, i need some help please.
The HP7694 is not a standalone version, I should use the GC EPC flow module to control the gaz flow and the gaz pressure. It is a G1289A headspace sampler.

If i have right, i need to connect the carrier gaz:
-Connect my gaz tank in the rear of my GC, in the EPC inlet
-Cut the carrier gaz line just before the split splitless inlet
-Connect a zero dead volume union on my carrier gaz line, and attached it with a new 1/16 tubing in the rear of the headspace.
-Connect a zero dead union on my transfer line and attached my transfer line with the rest of the small tube I cut previously, just before the split/splitless inlet
I am right?

How to connect the pressurization gaz? Directly attached at my gaz tank?

I read something about a auxiliary EPC module, i don't know if i need use it, and how to use it.

Need I change everithing on my S/SL inlet like the septum nut or the liner? I read the better liner for headspace analysis is a 2mm internal diameter.


Your help will be highly appreciated, because i don't want to pay an agilent service to install the headspace.

Thanks a lot!

Pierre

I think you've got it. You will need to tee off your carrier gas and connect this to the pressuruzation connection on the HS.

Be careful that you cut the correct line to the inlet. The correct one is 1/16", the septum purge line is metric. Cut the worng one and you'll be scrounging up a metric union to fix it. (Been there - got the T-shirt). I'd scrounge up a piece of 1/16" tubing and hold it up there for comparison first to be sure you're going to cut the right one.

I've never changed the liner/septa to do HS. That doesn't mean that it may not help.

Like you, I certainly wouldn't pay Agilent to do it.

Thank you very much for your reply.

I will install the HS in few days. I wait to receive unions and tubing to do it.

Have a good day,

Pierre

Hello,

I am sorry, i have another question :

To connect the pressurization line, I will install a Tee union but where exactly I will install it : Before the carrier gaz line enter in the GC or just before the carrier gaz line enter in the Headspace, so in other words : before or after the GC EPC inlet ?

What do you prefer, install the transfer line directly in the SSL inlet or with a needle throught the septum?

Tank you for all

Pierre

Bear in mind that connecting the transfer line to the stub of the inlet carrier gas input line puts a cold spot and bare metal into the sample path. This is not the most brilliant design that has ever entered a GC lab !

Peter

To cut the correct line, look at where the tubing enters the port. The one you want to cut is going through a flat portion of the weldment.

As for the cold spot I wouldn't worry about it. I run a 150:1 split so my total flow through the 1/16" tube is just under 100cc/min, doubt that anything condenses.

Yeah if properly installed the cold spot is not an issue for all but the most fickle of methods. You can also rig up ways of keeping that area heated or at least insulated.

The vial pressure should be supplied by aux EPC or by manual pressure control.

Hello Everybody!

Thank you for reply and your help!

I will install the HS directly in the s/SL and control the pressurization line with a pressure regulator (I don't have a auxilliary EPC and it's expensive to buy one)

Thank for all!

Pierre