Mouser, Paula 1-2

Measuring Oxygen, Nitrogen, and Carbon Dioxide on the HP 6890 GC and the TCD

Before you Begin:

1.  Change septum before every batch

  1. Remove the green nut from the top of column 1 with the supplied tool
  2. Be careful the machine inlet can be hot
  3. Use a needle to remove the old septum
  4. Insert new septum without touching the flat surface with your fingers
  5. Tighten the nut back on with your fingers
  6. Tighten the nut slightly again with the tool

2.  Turn the computer on

3.  Run “GC” located on the desktop

4.  Change the method to “OXY_CAL”

  1. This method uses the TCD with:
  2. oven temperature of 40oC
  3. flow rate of 6 ml/min
  4. inlet temperature of 230oC
  5. detector temperature of 230oC
  6. The column is the Supelco Carboxen-1010 PLOT
  7. 30 m long
  8. 530 um diameter
  9. The makeup and reference gas is helium

5.  After GC comes to levels defined in method OXY_CAL it will read ‘Ready’.

6.  If it shuts down before reaching a ready state, see troubleshooting section in manual

7.  Start a new sequence and save it under the desired name

Make up Standards:

1.  Flush out clean septum bottles with pure nitrogen or a combined N2/CO2 for 20 minutes using needle in-needle out.

2.  Cap and crimp closed

3.  Remove the same volume of gas you which to inject.

4.  Inject pure oxygen into the bottles to make headspace oxygen concentration (vol/vol%) standards of:

  1. 0%
  2. 2.5%
  3. 5%
  4. 10%
  5. 15%
  6. 20%

Load Sample with locking valve:

1.  Use a gas tight syringe (Hamilton)

2.  Remove 0.25 ml of your sample and inject into the front inlet.

  1. Close the needle valve before exposing to air.
  2. Be careful not to break the needle when inserting it into the bottle.
  3. Flush the needle five times before extracting a sample.
  4. Slowly remove 0.25 ml of gas
  5. Close the valve
  6. Remove the needle carefully
  7. Insert the needle into the front inlet
  8. Before opening the gas tight valve, compress the gas with the needle plunger
  9. Open the valve on the needle
  10. Inject the gas
  11. Wait 3 seconds
  12. Close the valve
  13. Remove the needle.

3.  Push the start button on the front of the machine

4.  Allow the program to run (60 minutes)

5.  Chemstation will try and integrate your peaks resulting in a window with your sample results.

6.  Keep these results or use the hand integrator.

7.  Print or record results

8.  Close the window.

9.  Record in the booklet:

  1. your name
  2. date
  3. sample
  4. volume injected
  5. detector used

10.  Run calibration standards

11.  Compare heights and areas to standard curve heights and/or areas to determine the gas %

Return the machine to non use conditions:

1.  Close the software

2.  On the front of the GC machine:

a.  View column 1

b.  Adjust the He flow rate to 1.0

c.  View Oven

d.  Adjust the temp to 100oC

e.  View front inlet

f.  Adjust temp to 100oC

g.  View front detector

h.  Adjust temp to 100oC

i.  Arrow down and turn both “Makeup gas” and “filament” Off

j.  Return the view to column 1

3.  Do not shut off carrier gas (Helium) or the GC!