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new gc/ms/ms operator
Posted: Mon Oct 05, 2009 2:20 am
by che313
hi every body
as a new gc/ms/ms operator and after trying with instruments' starting guide (the instrument is Agilent 7000 and the software is mass hunter) I've got up with unanswered questions.
1- how can I determine the precursor ion?
2- in same manner how to determine the product ion?
3- what is the importance for MRM?
4- what is the output of ms/ms? since there is no library to compare with??
Posted: Wed Oct 14, 2009 10:22 am
by che313
no experiance!!
Posted: Thu Oct 15, 2009 6:21 pm
by Bigbear
Look for the optimizer icon and read the help for it. the precursor ion depends on the nominal mass of your compound. This is how it's done in LC/QQQ so I'm assuming it's close to the same in GC/QQQ.
Posted: Fri Oct 16, 2009 3:39 pm
by Loekie
Set the instrument for Q1ms. Inject a reasoable amount. find your compound and determine the precursor ion. set the instruemnt up for full scan product ions and do incections with varing amounts of colision energy and determine the right product ions. after this you might want to optimize the colision energy for the selected transitions.
Nice that agilent is not helping you by telling how to use and setup your instrument
Posted: Fri Oct 16, 2009 3:42 pm
by Ron
If you don't have much mass spectrometer experisne I would strongly recommend that you take a course on GCMS. It doesn't have to be the Agilent course, atthough that will give you more information about using the instrument your company owns. A general course on mass spectrometry that includes tandem mass spectrometry would give you an understanding of the basic principles of setting up and optimizing a method.
Posted: Sun Oct 18, 2009 8:58 pm
by che313
thanks every body
bigbear: do you working with mass hunter?
loekie: I know that it goes in this why but my concern was which ion I have to select to be the precursor- what is the criteria? and the same question for optimised CE, low CE keeps the precursor but high ones eliminate it totally so what is the criteria here also to keep it or to eliminate it?
Agilent install the instrument only and give some introduction to mass hunter to run one ms only- they didn't told us even that ms2 need a procedure to work
ROn: any suggestions?
Posted: Mon Oct 19, 2009 10:06 pm
by Spectro
Hi che
Maybe it depended on the constract. My company bought a new GC-MS and Agilent helped setting up the instrument and the product ions as well.
Hi Ron,
I always have the trouble how to tuning the BFB. Do you think a mass spec class could hepl?
Thanks for reply.
Spectro.
Posted: Tue Oct 20, 2009 1:27 pm
by Bigbear
Yes che313 I sometimes use mass hunter. It's on our LC/QQQ's but I'm only a backup operator. I just took Agilent's LC/QQQ software class that deals with Mass hunter and found it very good.
I primarily am a GC/MS guy running chemstation.
Posted: Tue Oct 20, 2009 5:11 pm
by Loekie
I would start with the most intense peak in the spectrum that you are sure is from the compound of interest as a precursor ion. for the CE determination the precursor intensity is not important at all. You want to optimize the product ion intensity. On triple quads the product ion intensity does not have to maximize with the minimum precursor intensity
Posted: Tue Oct 20, 2009 7:30 pm
by yangz00g
If you have no previous experince, my suggestion is not to do it by yourself. It is time consuming, and requires certain level of understanding into the instrument and chmistry.
Literature search will help. If you use EI, most likely MRMs from the literature is readily usable.
Posted: Wed Oct 21, 2009 8:22 am
by che313
Bigbear - can we met on msn?
Loekie - thanks for your help, I'll do it in this way
yangz00g - I like to read and search and try, this is my pleasure.