By Inga Gupta on Thursday, March 7, 2002 - 08:25 am:
Could you please help me to find out whether I can do analyses on Varian CP-3800 GCMS , MS - Saturn 2000 with a CPSIL8MS capillary column (30 m , D 0.25mm) for gases like CO, CO2, CH4,C2H5 and N2. If not what system I can use. We try to inject samples with a syringe into the column but can not see any of these gases.
Thanks a lot,
Inga
By Anonymous on Thursday, March 7, 2002 - 08:57 am:
I am not familiar with the SPSIL8MS, butI have have performed the separation of all the gases you mentioned with a Carboxen 1006 PLOT column from Supelco (2-4241). You need to go sub-ambient to get separation of N2 and O2 with this column (~0C). I've used it successfully with GC-TCD and GC-MS EI, Agilent 6890/5973.
By Anonymous on Thursday, March 7, 2002 - 01:16 pm:
The column you are asking about is a semivolatiles column, so it will not resolve the gases, even with subambient cooling. A plot column is the way to go for this analysis. Call the column manufacturers and ask for their recommendation.
By Inga Gupta on Saturday, March 9, 2002 - 01:10 am:
Could you please tell me more about the conditions you used for the separation of these gases with a Plot column as temperature, time, flow rate etc. What do I need to do due to change the column I have got to a Plot column with a different ID as I couldn't find the Plot column with ID 0.25, only 0.32 and more. Is it going to be a problem if I change columns from time to time as we don't do gas analyses so often?
Thanks,
Inga
By Anonymous on Wednesday, March 13, 2002 - 08:33 am:
The Agilent 5973 can handle 0.32mm columns. You might be able to attach a 10m piece of 0.25mm fused silica between the detectora dn the column in order to allow the vacuum system to operate within the maximum flow rate.
Here are the conditions we use for our TCD analysis:
Carrier Gas: Helium
Carrier Flow: 1.8ml/min. at 0C
1.8mL/min for 3.5min.
1.8 to 2.6mL/min at 1mL/min.
2.6mL/min for 12min.
Injection Port Temperature: 200C
Detector Temperature: 150C
Column Oven Temperature: 0C-3.5min.
OC to 225C @ 24C/min
225C - 4 min.
Injection Type: Split
Injection Liner:Single Taper Liner
Split Vent Flow:15 mL/min
TCD Makeup Gas Flow:3.5 mL/min.
TCD Reference Flow:16 mL/min.
TCD Polarity:Time 0 (-) Polarity On
Time 2.1 (-) Polarity Off
Septum Purge Flow:0 (must be capped off)
Injection Volume:250uL
The TCD polarity is changed in order to detect H2 as a positive peak. The sensitivity is very poor for H2 when using He as a carrier. I believe -10 to -20C is necessary to separate O2 and N2.
Ret. Times
H2=1.8min.
Air=2.3
CO=2.7
CH4=4.6
CO2=6.7
H2O=8.5(broad)
MeOH=11.0
Good luck!
By inga on Thursday, March 14, 2002 - 04:58 am:
Thank you very much for your help!!!
I will try.
Inga
By titok aludi on Wednesday, March 24, 2004 - 10:05 pm:
Could you please help me to find out whether I can do analyses on GCMS a capillary column (30 m , D 0.25mm, 0.25micrometers) for gases like CO, CO2, CH4,C2H5 and N2. If not what system I can use. We try to inject samples with a syringe into the column but can not see any of these gases.
Thanks a lot,
titok
By Anonymous on Thursday, March 25, 2004 - 05:12 am:
You are probably scanning above the molecular weight. But what kind of ion are you creating?
Why not use a Helium Ionization detector?
Even with a properly configured TCD you can do low ppm levels.