Auto Sampler 1260 is Clog very high pressure

The auto sampler model G1329B 1260 is having high back pressure without column.

So far we had been doing the following:

  • Rotor seal is replaced 
  • Injection valve is cleaned
  • Metering Head is cleaned
  • Sample Loop is replaced
  • Needle seat is replaced
  • Needle is replaced
  • Pump is cleaned too.
  • All tubing lines connected to the injection valve were check one by one. Not clog
  • It's noticed that not solvent is coming out from  the injection valve to the column compartment.
  • Warm water was used to flush the system without column.

After all this procedure steps the back pressure still high.

What else we can do to prevent this issue again?

I noticed that several users have the same situation with this 1260 auto sampler.


Thank you

  • Don´t take it personally, but it´s certainly not a problem of this type of sampler (the G1329B is a very robust workhorse and it used to be our best selling vial sampler), but more a sign of insufficient sample preparation, poor quality of solvents or septa, insufficient lab housekeeping etc.


    You will have to trace the LC flow backwards: while pumping, open the fittings until you see the pressure dropping.


    Agilent offers some suggestions for best HPLC practices:

  • It's noticed that not solvent is coming out from the injection valve to the column compartment.

    Were is the solvent going then?

    Are you sure to have the rotor seal installed correctly and didn't overtighten the valve?

    Did you choose the correct replacement part?

    Did you check the connecting capillary from the injection valve o the column?


  • Hi Ankugler,


    Rotor was installed correctly. Valve was installed properly.

    All tubing lines were checked.

    Thank you.

  • So have you meanwhile been successfully in identifying the blocked part in your flow path?

    Switching the injection valve from main to bypass should be you first action.

    If the pressure drops rapidly while being in bypass you know that the culprit is somewhere in your sampler's flow path.

    Afterwards go back to mainpass and start disconnecting the different parts one by one.

    First is the needle seat capillary at the injection valve.

    • no change: continue with next connection
    • backpressure low: check valve, rotor seal and stator head (take off stator and check through-holes)

    Disconnect the loop from needle.

    • no change: continue with next connection
    • lower back pressure: blockage in needle or needle seat (most likely some culprit pressed into the needle seat, you can try to backflush the needle seat by de-installing it and connecting it to the purge valve outlet on the pump an put a beaker underneath). before doing this you should inspect the seat pill (the part of the needle seat where the needle is pushed into). In case the needle was not centered precisely after replacement, it most likely damaged the internal surface of the needle seat and seat material got compressed into the seat pill. In this case you should replace the needle and the seat and take care of precise needle center alignment (this must be done manually after needle installation, use the referring maintenance positioning functions of the Lab Advisor Software. A needle position offset can also result from using wrong vial caps. In case the seat is OK then it most likely is a blocked needle. In this case also replace the needle.   


    next steps would be the loop and the capillary between injection valve and metering


    have a successful troubleshooting if still required 


    best greetings


  • If you have flow going into the sampler at port 1 and nothing out of the sampler at port 6, what happens if you right click on the sampler icon and change the valve to bypass? 

    Not sure what software you are running but  Chemstation, OL 2 and Mass Hunter all allow you to switch to bypass.


    You replaced a lot and possibly the valve?

  • This question has been marked as assumed answered.

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