Hi everyone,
I am new to FAME analysis. I am trying to separate Supleco 37 Fame mix using the HP-5MS (30 m * 0.25 mm ID * 0.2 um thickness) column using the following protocol:
System: Agilent 7890A GC coupled with Agilent 5975C MS
HE flow rate: 1.2 mL/min
50 C to 180 C (15 C/min)
180 C to 230 C (2 C/min)
230 to 300 C (15 C/min)
Problems:
1. So far, my chromatogram has 33 peaks corresponding to 36 FAMEs (out of 37). I am not able to separate some of the C18 and C20 FAMEs. Any suggestions to improve the separation?
2. The Supleco Mix has cis and trans isomers of C18 FAMEs. Any idea which isomer elutes first from the HP-5MS column? Since cis and trans isomers have similar mass spectra, I am unable to identify the compounds.
3. If anyone is using the HP-5MS column for FAME analysis, could you please share your protocol and chromatograms? I would greatly appreciate it.
Thanks in advance for your help.
Firstly, modify the temp program. If the compounds are eluted during first ramp or few minutes after - change the first rate from 15 degC/min to 10 or 7 degC/min.
You should use split injection.
Can you post a chromatogram?
If everything is done well and after changes of temp prog. you still cannot separate these isomers = you need to get more selective column.
Regards
GB
Firstly, modify the temp program. If the compounds are eluted during first ramp or few minutes after - change the first rate from 15 degC/min to 10 or 7 degC/min.
You should use split injection.
Can you post a chromatogram?
If everything is done well and after changes of temp prog. you still cannot separate these isomers = you need to get more selective column.
Regards
GB
Unfortunately, 5-MS is not very suitable to separate all the FAMEs including isomer resolution. DB-23 or HP-88 is amenable to FAME analysis, you can have a look at this application sheet for a comparison of WAX and the aforementioned columns.
https://www.agilent.com/cs/library/applications/5989-3760EN.pdf
Hi Grzegorz Boczkaj,
Thank you for your response. Compounds that cannot be separated are eluting during the 180-230 C temp program. I tried to reduce the temperature ramp rate to 1C/min but it didn't help in the separation. I will now consider changing the column itself.
Hi İsmail Emir Akyildiz,
Thank you for your suggestion. I will check the application sheet for DB-23 and HP-88.
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