Chromatography Forum

Hello,

I have a DB-Wax column. The column had been baked 3 times. First time was trimmed and baked overnight. 2nd time was full maintenance, timmed and baked (no bleeding occured). Third time full maintenance, trimmed, and baked overnight again at 180 degrees. Then i ran some straight water and big column bleed starting occurring i am not sure that is the column destroyed?

We have an oxygen and moisture trap installed for the carrier gas helium. We did inject plant sample mixed with water, filtered and shoot. Now the column is bleeding too much. Can anyone please help what i can do to lower the bleed. Thank you in advance picture is also attached.


https://cdn.pbrd.co/images/HyZYSEW.jpg

Hi sohaib1,

Please, what was the temperature used to bake out the DB-WAX column each of the first two times? Also, what is the film thickness of the column?

Hi sohaib1,

Please, what was the temperature used to bake out the DB-WAX column each of the first two times? Also, what is the film thickness of the column?

180 degrees it was baked all the time. The column max temp is 250 degrees (260 degrees maximum isothermal). It is 28.01m * 250 um * 0.25 um

Thanks

Hi sohaib1,

Perhaps heating the column for one to two hours at 250 degrees Celsius will help with the bleeding--or for the method you are running, is the highest temperature no more than 180 degrees Celsius?

Note Slides 17 - 18

https://www.agilent.com/cs/library/esem ... olumns.pdf

Also, remember that water has a high expansion coefficient--it is easy to overload a column if care is not taken.

Hi sohaib1,

Perhaps heating the column for one to two hours at 250 degrees Celsius will help with the bleeding--or for the method you are running, is the highest temperature no more than 180 degrees Celsius?

Note Slides 17 - 18

https://www.agilent.com/cs/library/esem ... olumns.pdf

Also, remember that water has a high expansion coefficient--it is easy to overload a column if care is not taken.

For the method the max temperature is 240 degrees. Glycol requires high temperatures to get rid of it right.

We only injected 0.5um of water, because of its expansion volume.

Long ago i called Agilent and they said that always bake the column overnight.

Hi again,

Very well--perhaps heating the column overnight at a temperature between 220 - 250 degrees Celsius would be helpful in this case as 180 degrees Celsius seems to be inadequate.

My apology--without knowing the volume of the injector liner and head pressure it is difficult to speak further knowledgeably regarding the injection volume. If the liner for an Agilent GC, though, 0.5 uL of water may be overly large.

Hi again,

Very well--perhaps heating the column overnight at a temperature between 220 - 250 degrees Celsius would be helpful in this case as 180 degrees Celsius seems to be inadequate.

My apology--without knowing the volume of the injector liner and head pressure it is difficult to speak further knowledgeably regarding the injection volume. If the liner for an Agilent GC, though, 0.5 uL of water may be overly large.

Wont the polymer phase of the liner degrade more if heated again overnight at 220-250

The liner we are using is Agilent Ultra Inert Liner. The head pressure is around 10.961 PSI but pressure set point is 11 PSI

Agilent did say inject no more than 0.5um

Hi again,

You said:

Won't the polymer phase of the liner degrade more if heated again overnight at 220-250

The liner we are using is Agilent Ultra Inert Liner. The head pressure is around 10.961 PSI but the pressure setpoint is 11 PSI.

Agilent did say inject no more than 0.5um

I am unsure what you mean by "degrade" here--it is true that a higher temperature will allow more of the PEG stationary phase to be removed. This is the source of column bleed, to begin with, the removal of stationary phase upon heating. Bleed should decrease with a higher conditioning temperature. 240 degrees Celsius should not cause damage to the stationary phase as its isothermal limit is 240 degrees Celsius.

Make sure that whilst you condition the column that gas flow is being applied to the column, too.

Perhaps this will help:

http://lcgcindia.com/GC%20and%20GC%20MS ... n/pdf3.pdf

Also:

http://m.restek.com/images/calcs/calc_backflash.htm

I concur with Agilent's suggestion with the caveat that 0.5 uL of water injected is still too much for the liner. For example, 0.3 uL would not exceed the liner volume, assuming an inlet temperature of 250 degrees Celsius at a head pressure of 11 psi.

Hi again,

You said:

Won't the polymer phase of the liner degrade more if heated again overnight at 220-250

The liner we are using is Agilent Ultra Inert Liner. The head pressure is around 10.961 PSI but the pressure setpoint is 11 PSI.

Agilent did say inject no more than 0.5um

I am unsure what you mean by "degrade" here--it is true that a higher temperature will allow more of the PEG stationary phase to be removed. This is the source of column bleed, to begin with, the removal of stationary phase upon heating. Bleed should decrease with a higher conditioning temperature. 240 degrees Celsius should not cause damage to the stationary phase as its isothermal limit is 240 degrees Celsius.

Make sure that whilst you condition the column that gas flow is being applied to the column, too.

Perhaps this will help:

http://lcgcindia.com/GC%20and%20GC%20MS ... n/pdf3.pdf

Also:

http://m.restek.com/images/calcs/calc_backflash.htm

I concur with Agilent's suggestion with the caveat that 0.5 uL of water injected is still too much for the liner. For example, 0.3 uL would not exceed the liner volume, assuming an inlet temperature of 250 degrees Celsius at a head pressure of 11 psi.

OK thank you i will try to condition the column at higher temperature. Thank you

You are welcome and best wishes!