7 Replies Latest reply on Jul 18, 2018 5:11 AM by eme091

    Low level Oxygen and CO by 490 Micro GC in plant's nitrogen supply


      Utilizing a 490 Micro GC with a TCD and MolSieve 5A 20 m column we are attempting to determine the purity of our plant's nitrogen as Airgas( run the nitrogen generation plant on site) can not provide chromatography or proof of the 99.99% purity of their nitrogen.  We were told by the sales rep that the 490 micro GC can see down to the 5ppm levels of CO and O2 in nitrogen, but we have yet to obtain even a peak at 10ppm of either in a nitrogen balance.  Below is the system parameters we are currently running:

        1. Channel 1:

        i.    Carrier gas: Helium

        ii.    Description: 20m MS5A Unheated Injector,Backflush

        1. Injector:

        i.    Injector Time: 40ms

      ii.    Backflush time: 0s

        1. Detector:

        i.    Detector state: Checked

      ii.    TCD temp limit check: Checked

      iii.    Invert signal: unchecked

      iv.    Sensitivity: Auto

        1. Column and pneumatic:

        i.    Column temperature: 40°C

      ii.    Pressure mode: Static

        iii.    Initial Pressure: 200.0 kPa

        1. Signal Settings:

      i.    Acquire Channel: Checked

      ii.    Sampling Frequency: 100 Hz

      iii.    Run Time: 500 s

      iv.    Acquisition delay: 0 s

        1. Common:
      • Stabilizing Time: 5 s
      • Sample Time: 30 s
      • Continuous Flow: Off
      • Flush Cycles: 1 cycle
      • Injection Delay: 0 s


      Any suggestions are much appreciated.