Chromatography Forum

Hello,

i´am pretty new in GCMS (agilent 5975 msd, GC:6890, headspace) and i want to know, if i it is recommended to use sim/scan for every run i do within a storage test of certain samples (oxidizing ones). i wonder about the very high baseline when i do raw scan (it is about 1,000,000), when i do "normal" scan, it is just at 50,000 (the column is PEG).
If i do sim/scan i get really high peak areas and i wonder if the detection limit is decreased by raw scan...
since i do not really know which volatiles will be develop in my samples, so i usually do scan. i´m afraid nobody can help me at work and the informations in the manual are very scarce.

THANK YOU,
Propanal

Hello

Usually the SIM technique is used when you are looking and quantitate for specific compounds, trace analysis and so on, BUT it is mandatory that you have to know what you are looking for (ions to monitor ...)
Viceversa the scan mode is used for qualitative analysis.
Also, I usually suggest to run different autounes on running one or the other, indeed.

So my question is: wath kind of analysis you have to do ?
The new 5975 can run both techniques simultaneously, increasing the informations gathered in one shot, this is because you can see an higher signal ... Of course the data files takes more room, and so on ...

I could suggest you to run in scan mode until you have determined all the volatiles coming out of your sample.
I think indeed that a good method preparation in the HS side is necessary.

Hoping to be helpful
greetings

MSD5970

Hello,

i´am pretty new in GCMS (agilent 5975 msd, GC:6890, headspace) and i want to know, if i it is recommended to use sim/scan for every run i do within a storage test of certain samples (oxidizing ones). i wonder about the very high baseline when i do raw scan (it is about 1,000,000), when i do "normal" scan, it is just at 50,000 (the column is PEG).
If i do sim/scan i get really high peak areas and i wonder if the detection limit is decreased by raw scan...
since i do not really know which volatiles will be develop in my samples, so i usually do scan. i´m afraid nobody can help me at work and the informations in the manual are very scarce.

THANK YOU,
Propanal

if you register onto the agilent website there are some "e-seminars" which feature the 5975. If you go through the intro and overview to the 5975 there is a good description of the sim/scan mode explaining it out. i only found this out recently as we are in the midst of setting up a 5975 ourselves.

Also you can visit technical support site for FAQs at,
http://www.chem.agilent.com/cfusion/faq/faq.cfm