Chromatography Forum

Hello,

We have a Agilent 6890 GC with two injection ports and two FIDs and a GC-PAL autosampler. Our data system is ChemStation. We are using a fast isothermal method and I would like to be able to inject into both ports to maximize throughput. Can this be done and how would the sequence be set up to do this? Any advise is appreciated.

Thanks!

Hi,

You want to maximize the throughput,does it mean:
1) that you want to run like 2samples at the same time, one in each inlet/colum/FID system?
2)Or you want a dual column confirmation, the same sample injected into 2 different polarity columns?

If it's option 2) what I suggest is that you combine the 2 columns in 1 inlet and distribute then the signals to the 2 FIDs.
However if it's option 1) that's indeed more complicated,but maybe building 2 methods one with inlet back and the other with front and try to put in the sequence without prepahead?I'm just speculating....Have you check the manual for help already?
Regards,

Atom

Hi it's me again,

I just thought that if you have Gerstel Maestro software to control the MPS maybe try to use the Prepsequence option,there maybe you can get away and build a sequence with 2 methods injecting in 2 different inlets almost at the same time.I never tried dual injection in different inlets but if it's what you want give it a try...

Regards,
Atom

Hi Atom,

I actually want to do the first, inject two samples on two inlet/column/FID sets, with the second injection immediately after the first one. I'm not familar with the Gerstel software, but I was hoping to do it all through ChemStation. Thanks.

Hi,

You want to maximize the throughput,does it mean:
1) that you want to run like 2samples at the same time, one in each inlet/colum/FID system?
2)Or you want a dual column confirmation, the same sample injected into 2 different polarity columns?

If it's option 2) what I suggest is that you combine the 2 columns in 1 inlet and distribute then the signals to the 2 FIDs.
However if it's option 1) that's indeed more complicated,but maybe building 2 methods one with inlet back and the other with front and try to put in the sequence without prepahead?I'm just speculating....Have you check the manual for help already?
Regards,

Atom

When you set up a new method on the CTC panel there is an option for the method to be gc injection or dual gc injection. This should then give you a starting point for configuring the dual-channel injeciton.
As far as I know there is no way to control the CTC settings through the FID chemstation.

Rich

Scottjn,

Spuzzin hits on the key point. Can the CTC inject, either at the same time or even one right after the other (with one syringe) in it's software? Don't own a CTC so I, personally, don't have a clue. If so, the rest is a piece of cake. If you have a CTC manual, dig in to see if it will do injections one right after the other.....

Let us know and I think I can walk you through the rest.

Best regards.

Thanks. When using the CTC as the autosampler, you can only choose "front injector", then from within the CTC method you can choose inj1 (front) or inj2 (back). I don't see a way to setup dual injections, unless it can be done from cycle composer, which I'm not that familiar with.

When you set up a new method on the CTC panel there is an option for the method to be gc injection or dual gc injection. This should then give you a starting point for configuring the dual-channel injeciton.
As far as I know there is no way to control the CTC settings through the FID chemstation.

Rich

With the Cycle composer of CTC, it can be done.
You just need to make a new macro.
Start with a single GC-inj.
And place after the injection (to inj1), place on more injection (to inj2)
Not to difficult, but not easy to tell you over a forum.

We could make it for you it you want.
I'm working at ATAS GL International B.V.
We are a CombiPAL distributor with some addition parts for the CombiPAL made by us.

Thanks. I'm not all that familar with Cycle composer. So would this integrate with ChemStation?

With the Cycle composer of CTC, it can be done.
You just need to make a new macro.
Start with a single GC-inj.
And place after the injection (to inj1), place on more injection (to inj2)
Not to difficult, but not easy to tell you over a forum.

We could make it for you it you want.
I'm working at ATAS GL International B.V.
We are a CombiPAL distributor with some addition parts for the CombiPAL made by us.

Agilent has a driver for CTC CombiPAL.

The following is only useful for temperature gradient runs, that has an inital oven temperature that cold traps the analyte of interest onto the front of the column (i.e. not isothermal runs)

What I did is to to create two methods, one called eg frontinject.m, and the other, rearinj.m

rearinj.m is your standard method that you run, with the temperature gradient, that is of course saving both signal data from the FIDs, with same pressure program.

Frontinj.m, is a low oven temperature isothermal method, that performs the same injection port function as your rearinj.m, eg pulsed split-less @ ? pressure. the isothermal oven program is set to run for .5 of a minute

you then create a sequence that starts and alternates between the Frontinj.m and the Rearinj.m, as what you will be doing is ignoring the data from the Frontinj.m and only processing the data from the rearinj.m

this works, because the sample that you injected using the Frontinj.m has not shifted since it was cold trapped onto the front of the column as the oven temperature has not risen.

this technique works, and I have used it for a while.

if you run a lot of samples, or there there a large number of users who put their sample onto the GC,it is best to write an excel macro that will create a sequence, that they can copy and paste into the sequence table, as a common problem I found, could be usually traced back to errors in entries in the sequence table, not with the technique.

hope this answers your question

Alex

The macro editor is part of the Cycle composer (it is an option). If you go to program files\Pal System (default install) you should see Cycle Composer and if available Cycle Composer with Macro Editor
Select the later one to create the macro to do the dual injection.

Feel free to contact me at phlippemottay@brechbuehler.com for more info.

Philippe Mottay

Allowing for travel and syringe priming, the time delay between the two injections is about 15-20 seconds. Obviously, you don't need to rinse the syringe after the first injection because it is going into the same sample vial again.

Regards,

Ralph