Helium carrier gas [August 12, 2004]
Posted: Mon Aug 30, 2004 7:04 pm
By Anonymous on Thursday, August 12, 2004 - 07:15 am:
What happens when you forget to turn on the helium carrier gas cylinder and run your GC to warm up for a few hours? Is the column ruined?
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By Consumer Products Guy on Thursday, August 12, 2004 - 08:00 am:
Depends on type of column, and how hot you got it; try it out with known samples or standards, and compare separation, peak shapes, etc.
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By Mark on Thursday, August 12, 2004 - 08:30 am:
To Anonymous,
You might want to disconnect the column from the detector first and program the column up to its max to clean off any degrdation products and then reeconnect it to the detector before trying the test samples.
Regards,
Mark
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By anonymous on Friday, August 13, 2004 - 07:57 am:
How do we know that the column is ruined?
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By Mark on Friday, August 13, 2004 - 11:10 am:
To Anonymous
Best bet is to use some kind of standard test mix to evaluate the column, the kind of thing Alltech, Supelco, etc. sell for cap columns. A "bad" column will cause peak tailing on one of the analytes. For example if there are acidic active sites you would see the basic analytes tailing, basic active sites would cause acidic analytes to tail, if there is very extensive damage you would see poor efficiency for all of the analytes. Also if you are using an FID there should be a large amount of bleed from a ruined column which will give an elevated baseline as the column temperature rises.
Regards,
Mark
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By carla on Sunday, August 15, 2004 - 02:37 pm:
why should the column be ruined? no carrier gas, no analyte in the column!? if you install or change a column, you heat it for a few hours. I guess thats the same when you dont turn on the gas while a run.
peak tailing can have many other reasons!
if your column is ruined, your theoretical plates are are damaged.
seperation seems to be a good indicator for that, cause higher HEPT -> decrease in seperation????
but not for sure.
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By Ron on Monday, August 16, 2004 - 04:38 am:
If the column is heated with oxygen present the stationary phase is damaged to some extent. I certainly hope you don't heat up columns after installation without gas flowing for long enough to flush air from the column.
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By PLOT-column on Monday, August 16, 2004 - 07:07 am:
I once had the oven ON with no carrier gas flowing. The separation seems to be the same. The oven was at 75C.
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By Ron on Monday, August 16, 2004 - 07:16 am:
The degradation proceeds more rapidly as the temperature increases. Remember the old rule of thumb that reaction rate doubles with every 10C rise in temperature. 100C is usually assumed to be the cutoff to heat a column with no flow and see no oxidative damage to the column. If you are using a PLOT column you may be able to go to a higher temperature without damage, as the separation takes place on a solid material instead of on a polymeric liquid stationary phase.
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By Jason on Monday, August 16, 2004 - 07:35 pm:
Can SUPEL-Q PLOT column be used to separate alcohols?
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By jeffo on Monday, August 23, 2004 - 12:50 pm:
If your initial column conditioning step had no carrier gas- you would have problems. Once its conditioned it should be oK. However, never expose a column to oxygen
What happens when you forget to turn on the helium carrier gas cylinder and run your GC to warm up for a few hours? Is the column ruined?
-------------------------------------------------------------------------------------------------------
By Consumer Products Guy on Thursday, August 12, 2004 - 08:00 am:
Depends on type of column, and how hot you got it; try it out with known samples or standards, and compare separation, peak shapes, etc.
-------------------------------------------------------------------------------------------------------
By Mark on Thursday, August 12, 2004 - 08:30 am:
To Anonymous,
You might want to disconnect the column from the detector first and program the column up to its max to clean off any degrdation products and then reeconnect it to the detector before trying the test samples.
Regards,
Mark
-------------------------------------------------------------------------------------------------------
By anonymous on Friday, August 13, 2004 - 07:57 am:
How do we know that the column is ruined?
-------------------------------------------------------------------------------------------------------
By Mark on Friday, August 13, 2004 - 11:10 am:
To Anonymous
Best bet is to use some kind of standard test mix to evaluate the column, the kind of thing Alltech, Supelco, etc. sell for cap columns. A "bad" column will cause peak tailing on one of the analytes. For example if there are acidic active sites you would see the basic analytes tailing, basic active sites would cause acidic analytes to tail, if there is very extensive damage you would see poor efficiency for all of the analytes. Also if you are using an FID there should be a large amount of bleed from a ruined column which will give an elevated baseline as the column temperature rises.
Regards,
Mark
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By carla on Sunday, August 15, 2004 - 02:37 pm:
why should the column be ruined? no carrier gas, no analyte in the column!? if you install or change a column, you heat it for a few hours. I guess thats the same when you dont turn on the gas while a run.
peak tailing can have many other reasons!
if your column is ruined, your theoretical plates are are damaged.
seperation seems to be a good indicator for that, cause higher HEPT -> decrease in seperation????
but not for sure.
-------------------------------------------------------------------------------------------------------
By Ron on Monday, August 16, 2004 - 04:38 am:
If the column is heated with oxygen present the stationary phase is damaged to some extent. I certainly hope you don't heat up columns after installation without gas flowing for long enough to flush air from the column.
-------------------------------------------------------------------------------------------------------
By PLOT-column on Monday, August 16, 2004 - 07:07 am:
I once had the oven ON with no carrier gas flowing. The separation seems to be the same. The oven was at 75C.
-------------------------------------------------------------------------------------------------------
By Ron on Monday, August 16, 2004 - 07:16 am:
The degradation proceeds more rapidly as the temperature increases. Remember the old rule of thumb that reaction rate doubles with every 10C rise in temperature. 100C is usually assumed to be the cutoff to heat a column with no flow and see no oxidative damage to the column. If you are using a PLOT column you may be able to go to a higher temperature without damage, as the separation takes place on a solid material instead of on a polymeric liquid stationary phase.
-------------------------------------------------------------------------------------------------------
By Jason on Monday, August 16, 2004 - 07:35 pm:
Can SUPEL-Q PLOT column be used to separate alcohols?
-------------------------------------------------------------------------------------------------------
By jeffo on Monday, August 23, 2004 - 12:50 pm:
If your initial column conditioning step had no carrier gas- you would have problems. Once its conditioned it should be oK. However, never expose a column to oxygen