donjd2@yahoo.com
Super Administrator 
Posts 2
Registered 6/4/2002 Member Is Offline Mood: optimistic
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| posted on 6/1/2005 at 06:47 AM |
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What do you think about the new Agilent 5975 GC/MS?
Is it revolutionary, evolutionary or more of the same? Would you consider purchasing one?
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gregory.wolber@kodak.com
Newbie 
Posts 1
Registered 12/14/2004 Member Is Offline Mood: Not Set
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| posted on 6/1/2005 at 01:30 PM |
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Scan Speed Specification etc.
The ability to export methods sounds nice. Until you read the fine print, namely that you can only do this if you upgrade your 5973 to the newest
software. Only then can you export a 5973 method to a 5975.
What is so hard about writing software that can read a method from an older instrument? That should be trivial, they are both Chemstation ! Now,
software to import methods from other vendors - that would be new !
Agilent, and the other manufacturers continue to provide specifications that do not relate to what the users need to know. David's article
quotes the scan speed as "Scan rates up to 10,000 amu/sec [sic]". However, we do not scan over 10,000 amu (or m/z). We scan over a much
smaller range (e.g. 10 - 510 m/z).
After each "scan", the instrument must reset the electronics (return the quads to the starting voltages) in order to start the next scan,
and that also takes time. The number of scans per second cannot be simply calculated from "scan rate/scan range", since that ignores the
return time.
For example, a new 5973 with fast electronics scanning over a 200 m/z range can scan at 25 scans/second. However, dividing 10,000 amu/sec by 200 m/z
per scan gives a theoretical 50 scans/second. The return time has a huge impact !
Several manufacturers quote scan speeds of around 10,000 amu/sec. However, they all have different return times. In addition, just because the
instrument CAN scan that fast does not mean it will give good peak shapes and valid data.
What is needed is a specification that is clear, and relevant. For example, for a scan range of 10 - 510 m/z, what is the number of scans/second that
will give acceptable ion statistics for the 69/70, 219/220, and 502/503 ion pairs?
I will allow others who have more experience help define "acceptable", and what calculated statistics might be most relevant. David...?
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