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GC MS column problem
Posted: Thu Oct 12, 2017 12:13 pm
by ferish91
Hello.i have shimadzu gc ms with 5 ms universal column.when i run solvent asetonitril or hexan ms deteceted many siloxanes.what can i do?
Re: GC MS column problem
Posted: Thu Oct 12, 2017 12:19 pm
by Bigbear
How old is the column? Has it been at max T without gas flow? Try conditioning it.
Re: GC MS column problem
Posted: Thu Oct 12, 2017 12:26 pm
by ferish91
we analyzed phthalates with this column.in this method column temperature 300C. we used this method 1 months.Our column max temperature 350.
Re: GC MS column problem
Posted: Thu Oct 12, 2017 12:31 pm
by ferish91
How old is the column? Has it been at max T without gas flow? Try conditioning it.
we analyzed phthalates with this column.in this method column temperature 300C. we used this method 1 months.Our column max temperature 350.
Re: GC MS column problem
Posted: Thu Oct 12, 2017 1:10 pm
by Peter Apps
If you do not have oxygen and moisture scrubbers on you carrier gas just before the GC then get some. If you have them, replace them with new ones.
Peter
Re: GC MS column problem
Posted: Thu Oct 12, 2017 1:51 pm
by Consumer Products Guy
Hello.i have shimadzu gc ms with 5 ms universal column.when i run solvent asetonitril or hexan ms deteceted many siloxanes.what can i do?
Like others have posted: the siloxanes are typically from column bleed or septum bleed.
Re: GC MS column problem
Posted: Fri Oct 13, 2017 10:51 am
by anena
Hi
I would cut off 10-20cm of your column at the inlet end. Check your liner to see if it is dirty and replace your septum.
Then bake out the column (condition) for > 3h @ 300°C (make sure you have carrier gas flow). Also give attention to your carrier gas filters (scrubbers) as was mentioned by one of the other members of the group. If you still have significant Si-peaks, your column stationary phase is probably starting to break down, but if your column has only been used for a month, I would be very surprised.
In my opinion acetonitril is not an ideal GC solvent (boiling point a bit high, and very polar). Try to use tBME (tert-butylmethylether) instead.
Kind regards
anena
Re: GC MS column problem
Posted: Thu Oct 19, 2017 3:45 pm
by James_Ball
Another source of this contamination can be septa particles trapped in the liner. If you get these in the liner then each time you make an injection a little more of the siloxanes will be extracted and sent into the column.
Re: GC MS column problem
Posted: Thu Oct 26, 2017 7:49 pm
by dgomezibarra
Check what m/z are those silanes or siloxanes.
https://blog.restek.com/?p=10706 check this webpage where those peaks are explained.
Have a great day.