Abstract
    Electron capture negative ion (ECNI, or so-called “negative-ion chemical ionization”^1,2) mass spectrometry is a well-established technique in mass spectrometry.  It is a highly sensitive and selective method for detecting certain compound classes of environmental and forensic importance and the range of applications can be extended by derivatization with electrophilic substituents.  However, conventional gas-moderated ECNI suffers from some serious problems.  The bipolar plasma produced by the high-pressure ECNI ion source can lead to competing reactions and a lack of reproducibility.
    An alternative approach is to omit the buffer gas and form negative ions directly with a beam of electrons with low (0-10 eV) energies.  Jim Laramée³ and Max Deinzer⁴ have shown^5,6 that a trochoidal electron monochromator can have important applications in analytical chemistry and that the electron capture resonances for molecular and fragment anion formation are structure-dependent.  In a collaborative effort, JEOL USA, Inc. has refined the Oregon State monochromator design to increase the ionizing electron current to analytically useful levels (hundreds of microAmperes at near-zero electron energies).
    A Tuneable Energy Electron Monochromator (TEEM^TM) installed on a JEOL AX-505 mass spectrometer has demonstrated GC/MS detection limits in the low femtogram range.  The monchromator source has shown excellent reproducibility and absence of artifacts due to ion-molecule reactions, and it also has positive-ion applications.  We have examined a wide range of analytes including explosives, polychlorinated biphenyls (PCB’s), polynuclear aromatic hydrocarbons (PAH’s) organic acids, and DNA and RNA bases.  In collaboration with Prof. Kent Voorhees and Mike Beverly⁷ at Colorado School of Mines, we have recently demonstrated⁸ that the electron monochromator provides enhanced specificity and improved detection limits for the determination of dipicolinic acid (an indicator of spore-forming bacteria) in pyrolyzed bacteria.  The electron capture resonances for the formation of the nitro anion can be used to distinguish isomers of nitroaromatic compounds.  Molecular orbital calculations⁹ have been applied to understanding the behavior of the nitrotoluenes and the approach may lead to a more general understanding of the electron capture behavior of nitroaromatics..  It will also be shown that the electron monochromator can be applied to the detection of nitrated polynuclear aromatic hydrocarbons in diesel soot.   Most recently, we have collaborated with Harvard University Chemistry Department and Institute of Chemistry and Cell Biology to explore an application of the TEEM^TM to combinatorial chemistry¹⁰.    We have also adapted the TEEM^TM to fit on our larger (MStation^TM) and smaller (GCmate^TM) mass spectrometers.

References:
1 Hunt, D. F. Anal. Chem. 1978 50, 1781-1784.
2 Bowie, J. H. Mass Spectrom. Rev. 1984 3, 161-207.
3 Kansas City, MO (can be contacted through R. B. Cody at JEOL)
4 Oregon State University, Corvallis, OR
5 Laramée, J. A.; Mazurkiewics, P.; Berkout, V.; Deinzer, M. L. Mass Spectrom. Rev. 1996 15, 15-42.
6 Laramée, J. A.; Cody, R. B.; Deinzer, M. L. Encyclopedia of Analytical Chemistry (in press).
7 Eli Lilly, Indianapolis, IN
8 Beverly, M. B.; Voorhees, K. J.; Hadfield, T. L.; Cody, R. B. Anal. Chem. 2000 72, 2428-2432.
9 Cody, R. B.; Voorhees, K. J.; Eberhart, M. to be submitted for publication
10 Robert B. Cody, Elaine Cope Eatough, Jason Gatlin, Andrew N. Tyler, Michael Foley, to be submitted for publication.
 

Background
    I have been involved in mass spectrometry for over 25 years.  My first experience with a mass spectrometer was to use a Tesla coil to find and fix a leak in the glass inlet on a cycloid-tube residual gas analyzer at Roanoke College.  The Tesla coil made the leak larger, and the Torr-Seal and wooden applicator used to fix it wound up permanently affixed to my pants.
    Despite this experience, I enjoyed mass spectrometry and went on to graduate school to work with ion cyclotron resonance mass spectrometry at Purdue University.   I became one of the first four students in the late Ben Freiser’s ICR research group.  The idea of doing spectroscopy (photodissociation with a theatrical arc lamp and a welding power supply) in a mass spectrometer was intriguing.  I didn’t realize just how far from analytical chemistry we were at that time.  Ben had brought Terry McMahon’s combined trap/drift-cell ICR with him from CalTech.  This machine took up to an hour to scan the magnet at a maximum resolving power of 300 and an equivalent mass range (up to m/z 300).  If you forgot to turn on the “Scan” switch, then the chart recorder pen twitched in place until the red ink bored a hole through the paper and left a puddle on the table.  Things improved when we bought the very first commercial Fourier transform mass spectrometer from Nicolet.
    This was an exciting  time to be doing mass spectrometry at Purdue and there was a lot of collaboration and interaction between Ben’s group, Graham Cooks’ group, and Bob Squires.  My graduate thesis, “New Techniques in Ion Cyclotron Resonance Spectrometry” described three new experiments: (1) electron impact excitation of ions from organics (EIEIO, an early and not very useful forerunner of the electron-capture activation experiments that McLafferty has developed), (2) laser desorption in the trapped-ion cell to produce metal ions, and (3) the techniques for doing MS/MS in a trapped-ion mass spectrometer.  The laser desorption was an accident (the others were deliberate).   I was trying to do multiphoton ionization of salicylaldehyde and got the focal length of the lens wrong.   Because of spectacularly bad mass accuracy and unrecognizable isotope ratios, it took us two days to identify the silver ions that were being desorbed from the rhodium-flashed, silver plated copper back plate of the ICR cell.  Ben combined the laser desorption of metal ions with the MS/MS techniques and went on to explore the gas-phase reactivity of metal ions in great detail.
    After graduate school, I went to Nicolet in Madison, Wisconsin to continue working on FTMS.  I was fortunate to be able to collaborate with a number of well-known mass spectrometrists during this early period in FTMS history.  Unfortunately, the company didn’t realize the potential of the technology.  When Nicolet shut down the FTMS group, I left to go to work with JEOL USA, Inc.  Extrel bought the what was left of the Nicolet group a few months later and a few years later, it was bought by Finnigan and later shut down again.
    After working on FTMS for so long, I was surprised to see at JEOL just how routine magnetic sector technology had become.  While this is a relatively mature technology, the machines have become easier to operate and a great deal smaller.  Some of our research at JEOL USA, Inc. has involved:

• Interfacing an ESI source to magnetic sectors
• Applications of array detectors with single and tandem magnetic sector mass specs
• Development of the pulsed FAB technique with Andrew Tyler at Harvard
• Application of the sector/in-line TOF hybrid developed for CID/SID studies (presently in Vicki Wysocki’s lab at Arizona State)
• Commercial development and applications of the electron monochromator source based on research begun at Oregon State University
• Development of a new approach to high-throughput analysis based upon simultaneous sample measurement

Meeting details

Date:	Tuesday	April 24, 2001
Time:	6:00 pm	Social hour, registration (no-host cocktails)
	7:00 pm	Dinner
	8:15 pm	Presentation (free, no reservations required)
Dinner:	Choice of:	Breast of Chicken Chasseur (mushroom/tomato sauce)
		Salmon with Champagne sauce
		Vegetarian Pasta (penne and vegetables)
	includes	Soup, Salad, Dessert, Coffee, Wine.
Cost:	$25.00	BAMS members.  Reservations required by noon on Tuesday April 17, 2001
	$35.00	Non-members.  Reservations required by noon on Tuesday April 17, 2001
	$15.00	Students only.  Reservations required by noon on Tuesday April 17, 2001

Note: 2001 dues need to be paid to obtain member price.  Dues ($20) may be paid at the meeting

Maps & directions
The Basque Cultural Center
599 Railroad Avenue
South San Francisco, CA 94080
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Want to be a judge?  The Intel International Science & Engineering Fair 2001 needs you! See the call for judges and/or their web site.
 

The San Francisco Bay Area Mass Spectrometry discussion group was formed in 1980 to provide a regular gathering for people interested in mass spectrometry and allied topics. BAMS currently has a membership of about 280 individual and 20 corporate members, and meets 8-10 times per year for a midweek dinner and lecture.  Meetings attract between 30 and 90 people, and are held at a restaurant or hotel in the bay area convenient for our speaker.  We usually convene at 6:00pm for cocktails, dinner at 7:00pm, and lecture at 8:15pm.
 

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Last update: 4/10/01.