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By Anonymous on Thursday, November 6, 2003 - 10:41 pm:
Is triple quad is the solution or triple quad. My application is quantification,and imurity profile characterization and high sensitivity
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By Anonymous on Thursday, November 6, 2003 - 11:42 pm:
It seems that you are already biased towards buying a triple quad
.
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By MG on Friday, November 7, 2003 - 06:58 am:
I use both a modern ion trap and triple-quad (new models introduced within the past ~2 years). In general, the triple-quad will be better for quantitation, because you can do true MRM (aka SRM) experiments. That is, you have two mass analyzers and you are simultaneously monitoring your parent and daughter ions. It is easy and fast to monitor many MRM transitions. But for qualitative analysis, the quad will take more time to produce poorer quality spectra.
The ion trap will be better for qualitative analysis. Traps have better sensitivity in full-scan and product-ion modes, because the trap accumulates ions and then does the mass separation. The trap gives cleaner, less noisy spectra. Modern traps will probably have "data dependent" or "auto ms/ms" software, that allows you to collect full scan and product ion data in a single run. For quantitation, traps tend to be less linear in response than quads. Also for multiple compounds or ion pairs, the trap will tend to move slower than the triple-quads, and you'll get fewer points across your chromatographic peaks. This is because for each MS/MS experiment you are doing accumulate --> isolate --> fragment --> scan. For "pseudo-MRM", add another isolate step.
Of course, triple-quads can be used successfully for qualitative analysis, and traps can be used for quantitation. The vendors will remind you of this in their literature. Ask yourself what type of experiment you will be doing most often. And please don't just take my word for it. Ask as many other experienced folks as possible. Also if you have specific applications in mind, send samples to the instrument vendors and see what the data looks like.
Then there are the new "linear ion traps". These are built like triple-quads, but some of the quadrupole rods are used to do ion-trapping, and they are more expensive. They claim to have the benefits of ion traps without the downsides. I've never used one, so I don't have an opinion of their performance.
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By Anonymous on Friday, November 14, 2003 - 03:40 am:
could anyone give me a definition of mass resolution and how it is
calculated for a quadropole mass spectrometer. And please give me an idea how to find our m/e ions in ESI is singly charged or multiple charged
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By MG on Friday, November 14, 2003 - 07:19 am:
On the quads that I use, resolution is measured as the full peak width at half-maximum (FWHM). When operating in "unit" resolution mode (that is, you can resolve the difference of 1 m/z), the permissible FWHM is 0.6 to 0.8. With quads, if properly calibrated, this value of FWHM is generally fixed across the mass range. There is another number called "resolution" commonly used by mass spectrometrists, but it is more applicable to TOF's and sectors. On a quad, the "resolution" number would vary across the mass range. Our quads have a "high" resolution mode where the instrument is calibrated to a smaller value of FWHM, as well as a "low" resolution mode intended for use in quantitation with SIM or MRM.
Charge state can be determined by measuring the differences between isotope peaks. All organic compounds will show an "A+1" peak due to the small fraction of carbon-13. For singly charged ions, the "A+1" peak will be 1 m/z greater than your base peak. For doubly charged, it will be 0.5 m/z greater. For 3 charges, it will be 0.33 m/z greater, etc. You'll have to run your quad in a "high" resolution mode to adequately resolve these higher charge states.
Forgot to mention in my previous post that ion traps are better for resolving multiple charge states than quads, although it can be done on a quad. On the quad, you'll sacrifice sensitivity when the resolution is narrowed. On ion traps, the sacrifice is slower scan speed. I also forgot to mention that traps can do MS^n where triple-quads can't. But, there are some scan types, like neutral-loss and precursor-ion, that can be done on triple-quads but not ion-traps.
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By Anonymous on Friday, November 14, 2003 - 07:35 pm:
Dear MG
Thanks for your useful information.Can u brief me the advantages of triple quad over ion trap ( in General )
Thanks in advance
-------------------------------------------------------------------------------------------------------
By MG on Saturday, November 15, 2003 - 08:34 am:
To Anon, 7:35pm: In general, triple-quads are better for quantitation than ion traps. See above posts in this thread for more details.
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By ves on Tuesday, November 18, 2003 - 05:10 am:
Dear Anon, The following excerpt is a bit too much like having your cake and eating it, too. Hopefully it is correct.
Nature 424, 581 (31 July 2003); doi:10.1038/424581b
Mass spectrometry goes mainstream
DIANE GERSHON
Diane Gershon is assistant editor, Nature Medicine Technical Reports.
http://www.nature.com/cgi-taf/DynaPage. ... 1b_fs.html
"...The new 4000 Q TRAP LC-MS/MS system from Applied Biosystems in Foster City, California, and MDS Sciex in Concord, Canada, is a triple-quadrupole mass spectrometer where the last quadrupole can be operated as a conventional quadrupole mass filter or as a linear ion trap — an arrangement that allows decoupling of precursor ion isolation and fragmentation from the ion trap itself. The company says that this provides more sensitive tandem mass-spectrometry (MS/MS) and allows the identification and measurement of low levels of post-translational modification in a single liquid chromatography–MS/MS run. "This is one of the few instruments where you'd actually be able to do the protein identification work, protein characterization and absolute quantitation on the same instrument," claims Ron Bonner, director of applied research at MDS Sciex..."
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By Anonymous on Thursday, March 11, 2004 - 06:22 am:
It's clear that the 3Q is better for quantitation, but does it follow then that they are better for trace analysis than the ion trap? I guess what I'm asking, is which one will give the better LOD?
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By Anonymous on Thursday, March 11, 2004 - 06:56 pm:
Dear MG,
We are new to the LC/MS/MS. We would like to buy some good books on this subject. Can you recommend some books (recent), we are looking for a book(s)with a lot of applications and a good coverage of MS/MS.
Thanks
-------------------------------------------------------------------------------------------------------
By Jennifer on Tuesday, June 15, 2004 - 12:59 pm:
Just got a 4000 Q-Trap here. It rocks!
-------------------------------------------------------------------------------------------------------
By Anonymous on Friday, June 25, 2004 - 03:53 am:
I tend to buy TSQ from Finnigan, can anybody will share view about this machine
Is triple quad is the solution or triple quad. My application is quantification,and imurity profile characterization and high sensitivity
-------------------------------------------------------------------------------------------------------
By Anonymous on Thursday, November 6, 2003 - 11:42 pm:
It seems that you are already biased towards buying a triple quad
.
-------------------------------------------------------------------------------------------------------
By MG on Friday, November 7, 2003 - 06:58 am:
I use both a modern ion trap and triple-quad (new models introduced within the past ~2 years). In general, the triple-quad will be better for quantitation, because you can do true MRM (aka SRM) experiments. That is, you have two mass analyzers and you are simultaneously monitoring your parent and daughter ions. It is easy and fast to monitor many MRM transitions. But for qualitative analysis, the quad will take more time to produce poorer quality spectra.
The ion trap will be better for qualitative analysis. Traps have better sensitivity in full-scan and product-ion modes, because the trap accumulates ions and then does the mass separation. The trap gives cleaner, less noisy spectra. Modern traps will probably have "data dependent" or "auto ms/ms" software, that allows you to collect full scan and product ion data in a single run. For quantitation, traps tend to be less linear in response than quads. Also for multiple compounds or ion pairs, the trap will tend to move slower than the triple-quads, and you'll get fewer points across your chromatographic peaks. This is because for each MS/MS experiment you are doing accumulate --> isolate --> fragment --> scan. For "pseudo-MRM", add another isolate step.
Of course, triple-quads can be used successfully for qualitative analysis, and traps can be used for quantitation. The vendors will remind you of this in their literature. Ask yourself what type of experiment you will be doing most often. And please don't just take my word for it. Ask as many other experienced folks as possible. Also if you have specific applications in mind, send samples to the instrument vendors and see what the data looks like.
Then there are the new "linear ion traps". These are built like triple-quads, but some of the quadrupole rods are used to do ion-trapping, and they are more expensive. They claim to have the benefits of ion traps without the downsides. I've never used one, so I don't have an opinion of their performance.
-------------------------------------------------------------------------------------------------------
By Anonymous on Friday, November 14, 2003 - 03:40 am:
could anyone give me a definition of mass resolution and how it is
calculated for a quadropole mass spectrometer. And please give me an idea how to find our m/e ions in ESI is singly charged or multiple charged
-------------------------------------------------------------------------------------------------------
By MG on Friday, November 14, 2003 - 07:19 am:
On the quads that I use, resolution is measured as the full peak width at half-maximum (FWHM). When operating in "unit" resolution mode (that is, you can resolve the difference of 1 m/z), the permissible FWHM is 0.6 to 0.8. With quads, if properly calibrated, this value of FWHM is generally fixed across the mass range. There is another number called "resolution" commonly used by mass spectrometrists, but it is more applicable to TOF's and sectors. On a quad, the "resolution" number would vary across the mass range. Our quads have a "high" resolution mode where the instrument is calibrated to a smaller value of FWHM, as well as a "low" resolution mode intended for use in quantitation with SIM or MRM.
Charge state can be determined by measuring the differences between isotope peaks. All organic compounds will show an "A+1" peak due to the small fraction of carbon-13. For singly charged ions, the "A+1" peak will be 1 m/z greater than your base peak. For doubly charged, it will be 0.5 m/z greater. For 3 charges, it will be 0.33 m/z greater, etc. You'll have to run your quad in a "high" resolution mode to adequately resolve these higher charge states.
Forgot to mention in my previous post that ion traps are better for resolving multiple charge states than quads, although it can be done on a quad. On the quad, you'll sacrifice sensitivity when the resolution is narrowed. On ion traps, the sacrifice is slower scan speed. I also forgot to mention that traps can do MS^n where triple-quads can't. But, there are some scan types, like neutral-loss and precursor-ion, that can be done on triple-quads but not ion-traps.
-------------------------------------------------------------------------------------------------------
By Anonymous on Friday, November 14, 2003 - 07:35 pm:
Dear MG
Thanks for your useful information.Can u brief me the advantages of triple quad over ion trap ( in General )
Thanks in advance
-------------------------------------------------------------------------------------------------------
By MG on Saturday, November 15, 2003 - 08:34 am:
To Anon, 7:35pm: In general, triple-quads are better for quantitation than ion traps. See above posts in this thread for more details.
-------------------------------------------------------------------------------------------------------
By ves on Tuesday, November 18, 2003 - 05:10 am:
Dear Anon, The following excerpt is a bit too much like having your cake and eating it, too. Hopefully it is correct.
Nature 424, 581 (31 July 2003); doi:10.1038/424581b
Mass spectrometry goes mainstream
DIANE GERSHON
Diane Gershon is assistant editor, Nature Medicine Technical Reports.
http://www.nature.com/cgi-taf/DynaPage. ... 1b_fs.html
"...The new 4000 Q TRAP LC-MS/MS system from Applied Biosystems in Foster City, California, and MDS Sciex in Concord, Canada, is a triple-quadrupole mass spectrometer where the last quadrupole can be operated as a conventional quadrupole mass filter or as a linear ion trap — an arrangement that allows decoupling of precursor ion isolation and fragmentation from the ion trap itself. The company says that this provides more sensitive tandem mass-spectrometry (MS/MS) and allows the identification and measurement of low levels of post-translational modification in a single liquid chromatography–MS/MS run. "This is one of the few instruments where you'd actually be able to do the protein identification work, protein characterization and absolute quantitation on the same instrument," claims Ron Bonner, director of applied research at MDS Sciex..."
-------------------------------------------------------------------------------------------------------
By Anonymous on Thursday, March 11, 2004 - 06:22 am:
It's clear that the 3Q is better for quantitation, but does it follow then that they are better for trace analysis than the ion trap? I guess what I'm asking, is which one will give the better LOD?
-------------------------------------------------------------------------------------------------------
By Anonymous on Thursday, March 11, 2004 - 06:56 pm:
Dear MG,
We are new to the LC/MS/MS. We would like to buy some good books on this subject. Can you recommend some books (recent), we are looking for a book(s)with a lot of applications and a good coverage of MS/MS.
Thanks
-------------------------------------------------------------------------------------------------------
By Jennifer on Tuesday, June 15, 2004 - 12:59 pm:
Just got a 4000 Q-Trap here. It rocks!
-------------------------------------------------------------------------------------------------------
By Anonymous on Friday, June 25, 2004 - 03:53 am:
I tend to buy TSQ from Finnigan, can anybody will share view about this machine
