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Degassing hexane
Posted: Sun Jun 01, 2014 5:36 am
by riya
Can hexane be degassed?? For how much time?? As its boiling temperature is 68 degree, it will get heated up.
If hot hexane passed through hplc tubing during purging for 1-2 min can it be damaging for the system??
As I am getting staright baseline with 100% Isopropanol and not with 100% hexane?? Can it be due to passage of hot hexane but isopropanol was also degassed but not passed hot while purging.
Re: Degassing hexane
Posted: Sun Jun 01, 2014 9:23 am
by Peter Apps
If you are degassing by purging the hexane will be cooled by its own evaporation, not heated up.
Peter
Re: Degassing hexane
Posted: Sun Jun 01, 2014 4:21 pm
by dblux_
Can hexane be degassed?? For how much time?? As its boiling temperature is 68 degree, it will get heated up.
If hot hexane passed through hplc tubing during purging for 1-2 min can it be damaging for the system??
As I am getting staright baseline with 100% Isopropanol and not with 100% hexane?? Can it be due to passage of hot hexane but isopropanol was also degassed but not passed hot while purging.
Have you really degassed hexane by heating it to boiling state and then pumped hot to the system ?
Although I'm not a cleaner here, but could this strange post be moved to Liquid Chromatography forum ?
Re: Degassing hexane
Posted: Sun Jun 01, 2014 5:13 pm
by riya
If you are degassing by purging the hexane will be cooled by its own evaporation, not heated up.
Peter
I am degassing by using sonicator water bath and I degassed it for 15-20 min so it got heated up in the meantime.....its temperature was around 70-80 degree....and I passed it through system but not through column.....
Can baseline be not coming straight due to hexane.....as with IPA it is straight when passing through column....
Re: Degassing hexane
Posted: Sun Jun 01, 2014 5:17 pm
by riya
Can hexane be degassed?? For how much time?? As its boiling temperature is 68 degree, it will get heated up.
If hot hexane passed through hplc tubing during purging for 1-2 min can it be damaging for the system??
As I am getting staright baseline with 100% Isopropanol and not with 100% hexane?? Can it be due to passage of hot hexane but isopropanol was also degassed but not passed hot while purging.
Have you really degassed hexane by heating it to boiling state and then pumped hot to the system ?
Although I'm not a cleaner here, but could this strange post be moved to Liquid Chromatography forum ?
It is moved......
Re: Degassing hexane
Posted: Sun Jun 01, 2014 6:36 pm
by dblux_
I am degassing by using sonicator water bath and I degassed it for 15-20 min so it got heated up in the meantime.....its temperature was around 70-80 degree....and I passed it through system but not through column.....
Then your column stays intact. BTW - I would rather degass it by filtration through PTFE membrane filter under vacuum than by sonication.
Can baseline be not coming straight due to hexane.....as with IPA it is straight when passing through column....
In my opinion contaminants in hexane may be the culprit.
Re: Degassing hexane
Posted: Sun Jun 01, 2014 6:37 pm
by dblux_
It is moved......
Only the administrator can move it
Re: Degassing hexane
Posted: Sun Jun 01, 2014 7:58 pm
by Peter Apps
If you are degassing by purging the hexane will be cooled by its own evaporation, not heated up.
Peter
I am degassing by using sonicator water bath and I degassed it for 15-20 min so it got heated up in the meantime.....its temperature was around 70-80 degree
since hexane boils at 69C it cannot have reached 70 - 80 C unless it was under pressure, which would have defeated the object of degassing it. Try degassing for a shorter period, if you are still seeing bubbles evolving after 15 min it is because the hexane is boiling, not because there is still dissolved air coming out of it.....and I passed it through system but not through column.....
Can baseline be not coming straight due to hexane.....as with IPA it is straight when passing through column....
Re: Degassing hexane
Posted: Mon Jun 02, 2014 10:06 am
by lmh
if you want to sonicate without heat, you could try degassing by other means. I am very unconvinced by sonication, especially in a water bath type sonicator.
Many years ago, a few of us tried it. We happened to have a portable oxygen measuring probe, and were getting fed up with an HPLC technician who sonicated their buffers in a water-bath in our rather small lab for hours every day, and was doing our ears.
We shook a bottle of water ferociously to get it saturated with air, and took an oxygen reading, getting 100% saturation. We sonicated for 30 minutes, which reduced the oxygen saturation of the water to 99%.
We then stirred under tap-pump-vacuum for about half a minute, and got it down to 10%.
Sonication is supposed to work by causing cavitation, into which the gases evaporate, to create proper bubbles; I think you need a far more ferocious sonication to create cavitation than most hplc labs have available. The only mechanism in action in a typical lab is a vague hope that any dissolved gasses will find the noise so irritating they'll run away of their own accord...
Re: Degassing hexane
Posted: Mon Jun 02, 2014 11:28 am
by Gerhard Kratz
Degassing with Helium or a vacuum degasser will help you. Vacuum degasser please ask the manufacturer that the tubings are resistant to Hexane.
Good luck.
Re: Degassing hexane
Posted: Mon Jun 02, 2014 12:41 pm
by dblux_
Don't shoot to the sparrow with the cannonball. Start with simple, affordable solution
http://www.basinc.com/mans/LC_epsilon/P ... obile.html
Re: Degassing hexane
Posted: Mon Jun 02, 2014 5:55 pm
by riya
Thankyou all for your suggestions...... I will try them and try to solve the problem...........
Re: Degassing hexane
Posted: Tue Jun 03, 2014 6:49 am
by asm
Are you sure, that your problem is caused by solved gas and not by hexane itself due to its own vapor pressure?
When I used hexane with a normal phase column I ever had the problem, that I got bubbles in my HPLC from hexane itself. The backpressure was just to low. I could avoid that problem by using a mixture of hexan and a second solvent (in my case I used Ethyl acetate).
Re: Degassing hexane
Posted: Tue Jun 03, 2014 9:03 pm
by DJ
I'm a fan of the helium sparge. I think it is a gold standard of sorts for degassing.
Re: Degassing hexane
Posted: Wed Jun 04, 2014 7:21 am
by Peter Apps
I'm a fan of the helium sparge. I think it is a gold standard of sorts for degassing.
Helium sparging of a volatile liquid like hexane will evaporate more hexane than goes through the column !
Peter