Subject: Re: Mass Spec Interpretation Question
From: cody@jeol.com (Chip Cody)
Date: 25 Nov 1996 11:18:37 -0500
In <574rr6$og5@acmex.gatech.edu> sappenfilde@baylor.edu (Eric Sappenfield) writes:
}I'm trying to interpret a mass spec of [(n-C4H9)4N]3 Sc(CNS)6
}(MW=1120) and do not understand the fragmentation pattern. The
}peak with the highest m/e is at 1362 which corresponds to the
}molecular ion (1120) plus one [(n-C4H9)4N] group (242). The
}molecular ion peak at 1120 is missing. The x-ray crystal
}structure gives the expected molecular formula. Can someone
}explain this phenomenon?
}******************************************************************
}The preceding is my opinion and only my opinion and has nothing to
}do with the organization I work for.
}Eric Sappenfield Chemistry Department
}sappenfilde@baylor.edu Baylor University
} Waco, Texas 76798
}******************************************************************
If you are using FAB, ESI or a similar ionization method, you will need
a net positive charge to see the compound in (positive-ion) mass
spectrometry. Otherwise, the electric and magnetic fields cannot exert
a force on the molecule so that the mass spectrometer can do its job.
The structure that you describe has three cations and three anions,
with a net neutral charge. You need to form a charged species in order
to detect the compound by mass spectrometry. What you will usually see
is the gain of an extra cation, or the loss of one anion to leave you
with a net positive charge. This is very common.
--
=========================================================================
|____________
|_ Robert B. Cody, Ph.D
|________________________________ Applications Manager
|__ Mass Spectrometry
|________________________ JEOL USA, Inc.
|_
|__________ http://www.jeol.com
|_ e-mail: cody@jeol.com
=========================================================================
Subject: Re: Mass limitation on a Trio 1
From: dwh@cam.org (David Heywood)
Date: 25 Nov 1996 17:35:13 -0500
Hi Pascal,
A couple of years ago Fisons did offer an upgrade to the electronics which
gave an extended mass range upto 2000amu. I don't know whether this is
still available or not, you would have to contact Thermo Instruments.
Dave Heywood
Micromass Canada Inc.
Tel: 514 694 1200
Fax: 514 694 6280
In article <574ekt$ntq@acmey.gatech.edu>, proulxp@ERE.UMontreal.CA says...
}
}We builded an electrospray source to be used on a Trio 1 quad-MS.
}The design was adapted from Chait (probe-type ES source).
}
}Unfortunately, the VG-Trio 1 has a full scan limit at 1023amu.
}Is there a way to scan beyond this limit to 1500-2000amu
}at the price of lower resolution of sensitivity?
}
}We use MassLab on that particular MS.
}
}Regards,
}Pascal Proulx
}Universite de Montreal
}proulxp@ere.umontreal.ca
}
}
Subject: Screen Capture from Varian Saturn or Finnigan ITD
From: Don Magin
Date: 25 Nov 1996 17:35:27 -0500
The data system for older Finnigan ITD and Varian Saturn systems is a
DOS-based program. It will run under Windows, but within a window it
runs very slowly; as a full-screen application, it isn't too bad. When
I needed to use graphical data (spectra or chromatograms) for a paper,
presentation, or report, I would have to start the data system from
Windows (3.1), run it as a full-screen application until I got to the
screen I wanted, then switch to the run-in-a-window mode in order to copy
the screen to the clipboard. Then I would minimize the MS data system,
and paste the screen image into a graphics package. Then a switch back
to full screen mode to go to the next image I wanted, and repeat the
cycle.
I found a neat DOS-based screen grabber which works very well with the
data system running in DOS. It is a TSR which is invoked by a hotkey
combination. It saves the screen to a file in a directory which you can
specify, but it requires a different program to convert it to a .GIF file
(the utility to do this is included with the screen capture program, and
can be run in a batch mode). Best of all, it's freeware. It is called
CAPTUR22, copywrighted by Henrique Avila Vianna (1994), and is available
as CAPTUR22.zip from 'www.shareware.com' (which is a great site!);
search for it by name from files for the DOS platform.
Now, when I have the screen I want to capture up, I just press
C and a file appears in the directory of my choice. It even
has the ability to automatically capture the screen every so many seconds
up to a maximum of a specified number of screens (e.g., capture the
screen every 10 seconds up to a maximum of 20 screens). The files are
saved as PICTnnnn.CAP files, but a batch command will convert all of them
to the corresponding .GIF files. It even preserves the color display of
the Saturn (which saving to the clipboard doesn't).
I plop these .GIF files right into Microsoft PowerPoint for
presentations. I have printed them out using a color ink jet printer
on special glossy paper, and matted them as poster presentations.
