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GPC Agilent 1200/1100 system - baseline issues

BChristle78

Hi,

Our system consists of the following components and stacked like that from top to bottom:

  • Tray with THF Bottle as solvent A/no solvent B and Waters in Line Degasser
  • 1200 Series G1312A Binary Pump
  • 1100 Series G1313A Autosampler
  • 1100Series G1316A Column Compartment with guard column and analytical column in sequence
  • 1200 Series G1362A RI Detector

I am assessing the instrument as it has been sitting for a long time and was not in use.

When I run the system as it is set up with a flow of 1 ml/min and temperature of columns and RI at 55C, this is what I see:

When I change the flow to 2 mL/min the freqency observed of the rhythmically varying baseline does not change (approximately 13 s-1). From what I understand is that that behavior is not caused by the pump as if it was that frequency would change proportionally with the flow.

If I bypass the degasser using degassed THF, this is what I see:

To me that means that the wavy part of the noise came from the degasser, but there still is noise in the system.

After purging RID reference cell (did not know I had to do this as I am just learning about GPC) and changing the T to 35C (to not be at the limit of the temperature range for RID in case that matters). 

After equilibration over night, this is what I see:

I then bypassed sample port and column

It seems that there is quite a lot of noise still. Do I need to purge the system in a certain way in case there are bubbles, etc? Any feedback is welcome on how to further assess and optimize.

Best, Bettina

Parents
  • 0

    Do you have a Bubble Trap installed?

    In our experience, the pulling from the water in the discharge is enough to create issues in the baseline. We always set up the RIDs with a bubble trap whose level is over the detector. As shown in the pictures

  • +1 in reply to santanacarballo

    I'm not into GPC, but for a standard RID setup we recommend quite a few things in order to get a stable baseline:

    A clean (no contaminations) and stable (p,T = const.) system is absolutely vital
    Position the solvent and waste bottles correctly: ABOVE(!) the detector
    Use the correct solvents (HPLC grade, stabilized e.g. for THF)
    Recommended is an isocratic pump
    If a quaternary pump is used, bypass the MCGV
    If a binary pump is used, run pre-mixed solvent 50:50 channel A and B from same bottle
    Check for leaks (pressure test for system, except RID, tighten fittings on RID)
    Set the temperature of the optical unit to at least 5 degrees above ambient, 10 degrees above ambient temperature would be better
    Verify inlet frit, pump filters and fittings quality
    The TCC/MCT needs to be set to the very same temperature as the optical unit

  • 0 in reply to sschombu

    Thank you very much. Ok. I will need to make sure out T/p is stable in the lab. We have a binary pump and I am using only THF running them through channel A and B from the same bottle. Temperature is set to 35C and ambient is approximately 22C. I will go through the parts you suggested and replace them if needed. They have been in the instrument for a long time. Maybe time to change them out.

    Can you tell me how to do a pressure test or in which manual I can find this information?

    What is TCC and MCT? 

  • 0 in reply to BChristle78

    Both are ovens. TCC is the old G1316A/B/C, where MCT is the new G7116A/B

    For a pressure test you will need the LabAdvisor software and it will guide you through.

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