GC MS column problem

Discussions about GC and other "gas phase" separation techniques.

9 posts Page 1 of 1
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?
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.
Bigbear wrote:
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.
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
Peter Apps
ferish91 wrote:
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.
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
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.
The past is there to guide us into the future, not to dwell in.
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.
9 posts Page 1 of 1

Who is online

In total there is 1 user online :: 0 registered, 0 hidden and 1 guest (based on users active over the past 5 minutes)
Most users ever online was 1117 on Mon Jan 31, 2022 2:50 pm

Users browsing this forum: No registered users and 1 guest

Latest Blog Posts from Separation Science

Separation Science offers free learning from the experts covering methods, applications, webinars, eSeminars, videos, tutorials for users of liquid chromatography, gas chromatography, mass spectrometry, sample preparation and related analytical techniques.

Subscribe to our eNewsletter with daily, weekly or monthly updates: Food & Beverage, Environmental, (Bio)Pharmaceutical, Bioclinical, Liquid Chromatography, Gas Chromatography and Mass Spectrometry.

Liquid Chromatography

Gas Chromatography

Mass Spectrometry