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  • 1.  Waters 7725i HPLC Injector

    Posted 01-30-2023 09:57
    good morning, I am using a Waters 1525 pump with a 7725i manual injector.  When the injector is in "inject" mode, everything flows correctly.  When we put it into "load" mode the flow stops and the pressure goes up until it faults.  I have changed the rotor seal and the stator face and I still have the same problem.  I also checked the flow into each position of the stator and they seem to be okay.   Does anyone have any ideas on where to go next before I change the entire manual injector?   thanks!  Jodie

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    Jodie Franklin
    Research Associate
    Johns Hopkins Univ/Sch of Med
    Baltimore MD
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  • 2.  RE: Waters 7725i HPLC Injector

    Posted 01-31-2023 10:43
    Hi Jodie,
    I'm assuming you can load the loop with the syringe and some liquid actually comes off of one of the drain connections (see http://www.hplc.ru/catalogs/hplc_7725-9725_injectors.pdf for drawings). Then none of the tubing is clogged, so it must be one of the channels in the rotor/stator (I don't know which part has the channel grooves). 
    If sonicating all the parts does not help, I'd suggest connecting it in the opposite direction (swapping pump and column connections) and trying to push some liquid through.
    hope this helps.
    zdenek

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    Zdenek Svindrych
    Research Scientist
    Dartmouth College
    Lebanon NH
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    Original Message


  • 3.  RE: Waters 7725i HPLC Injector

    Posted 01-31-2023 11:08
    Hi Zdenek, I actually cannot push liquid into the loop in the load position and then I over pressure.  I've looked at the injector schematics and in the inject position it is flowing from the pump into the loop and then out to the column utilizing 4 of the ports.  When it is in the load position, it flows from the pump to the column bypassing the loop.  I cannot wrap my head around why it cannot flow from the pump straight to the column bypassing the loop.  All of the ports are flowing at one point or another.  I will try the swap you mentioned and see what happens.  Thank you!

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    Jodie Franklin
    Research Associate
    Johns Hopkins Univ/Sch of Med
    Baltimore MD
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    Original Message


  • 4.  RE: Waters 7725i HPLC Injector

    Posted 01-31-2023 11:35
    Oh, I always confuse the Load and Inject positions...
    This is strange. Is there a way to assemble the valve incorrectly? Like one of the parts rotated 180 degrees out of position? I can't think of anything else that might cause the behavior you've observed...

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    Zdenek Svindrych
    Research Scientist
    Dartmouth College
    Hanover NH
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    Original Message


  • 5.  RE: Waters 7725i HPLC Injector

    Posted 01-31-2023 11:58
    I would have definitely thought I had assembled the valves incorrectly except the flow was stopping when I put it to the load position before I even took the injector apart to change the rotor seal and stator face.  I thought for sure one was stuck or something and that changing them would fix the problem...no such luck.  I was trying this forum for one last ditch effort but I think I'm just going to order a new injector.  I believe I have tried everything else.  Thanks for your response!  Jodie

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    Jodie Franklin
    Research Associate
    Johns Hopkins Univ/Sch of Med
    Baltimore MD
    ------------------------------

    Original Message


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