While using GC Sampler 80 for headspace analysis, is there a way to delay the split flow so that the split won't be turned on during sample incubation?

We have a 7890A coupled with GC Sampler 80. I noticed that when we use a split method, the split flow will be turned on in the beginning of the incubation. This is quite a waste of helium gas in my opinion. I have tried to look for any delay settings and was not able to find any. Am I missing anything? Is there any way to save helium?

  • While waiting for any answers, I'd like to add some of my thoughts.

    Based on my previous experience on Gerstel TDU/CIS inlet and Axel LC/GC inlet, those inlet flow and split vent (or equivalent vent) were both controlled by a separate in/out flow device built by Gerstel/Axel. I wonder if it was due to the control of the inlet timing. But since this autosampler was installed with imbedded Agilent method, I wonder if there might be a solution.

  • How high a split flow are you using?    Is Gas Saver turned ON in your method?  --like Gas Saver ON, 20 ml/min at 2.00 minutes.      Make sure not to go lower than 20 ml/min as there is a chance of back diffusion of air into the inlet any lower. If you run an oven temperature profile that goes hotter than 250° C, I'd even say that the gas saver should be set to 30 ml/min or even higher to avoid any possibility of oxygen damage to the column.

    What CTC cycle are you using?  Does it list A-xxxx or is it a non-Agilent CTC cycle? 

  • Hi Paul, thank you for your response! the method uses 100:1 split. (I know this is high.... We can try reduce it to 10 or 20). Gas saver is on at 20mL/min at 10 min. I like the info about the oven temp - gas saver flow. Ours goes up to 270 degrees. I'm not sure what CTC cycle mean. The autosampler we are using has these info: CTC Analytics AG, Part# MN01-02; Agilent G6501B.

  • 100:1 is not high at all. I've used 500:1 and 1000:1 for a few applications.  

    The CTC cycle used is important. If you edit entire method and step through the screens, you should come to one that looks like this. Where it says GC-Inj -- which one are you using?  If you click on the arrow it will drop down a list.  One should be something like A-HDSPC ...or something like that, it's been too long, but certainly starting with A-xxxxxx .  Select that cycle, save the method with a new name, and test it.  The A-xxxx cycles should turn the gas saver off just before each run rather than before the sequence starts.

  • Thank you Paul! The instrument is running right now. I will definitely try it next week! 

  • Hi Paul, I finally got a chance to twork on this one today. The one we are using now is HS-inj with 2.5mL HS syringe installed. I went ahead and found A-HS-Inj in the dropdown list. But I was given a msg: Object in Atom issued is not an object. I guess I will have to configure that? I couldn't find where to change the injector except at under Instrument, this was "CTC-PAL Reset Injector". Is this where I should go? I hesitated to click on this one without checking wtih you. Without much knowledge on this CTC I'm worried that if I change something I may not be able to change it back.

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