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From: Don Magin <MAGIND@md.AHP.COM>
Date: Thu, 27 Jun 1996 18:35:50 -0400
Subject:  CI reagent gas

At the ASMS meeting this year there were two posters
presented by Munson's group using a "methane/ammonia
(3%)" reagent gas for CI.  Was that 3% ammonia in
methane, or 3% methane in ammonia?  I thought it was 3%
ammonia in methane, but none of the compressed gas
suppliers I contacted would make it.  Could it have been 3%
methane in ammonia?  Whichever it is, can anyone tell me
who can supply it?
-- Don


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From: mrheadmstr@aol.com (MrHeadmstr)
Date: 30 Jun 1996 11:44:38 -0400
Subject: Re: CI reagent gas
Organization: America Online, Inc. (1-800-827-6364)


Since both methane and ammonia are commonly used reagent gases, I would
bet they simply fed both gas lines into a gas blending valve and varied
the ratios until they got the results desired.

You won't find such blending valves in the Alltech or Supelco catalogs,
but I would think a petroleum or refinery supply company would have such
things in a catalog.

PS.  Since I wasn't at ASMS and haven't read any papers presented there,
could you summarize the work for which this gas mix was used?  TIA



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From: cody@jeol.com (Chip Cody)
Subject: Re: CI reagent gas
Organization: JEOL USA, Inc.
Date: Mon, 1 Jul 1996 13:41:23 GMT



This idea was presented by P. Rudewicz and B. Munson a long time ago, and I
had some fun with it myself a few years ago.  The point is that ions
formed by ammonia chemical ionization can react with neutral ammonia.a
This can cause a loss of analyte ion current ([M+H]+ or [M+NH4]+).
Therefore, the better approach is to use a few percent ammonia in
methane so that the [NH4]+ reagent ions are produced in abundance, but
the neutral environment is dominated by methane molecules, which do
not back-react with the analyte ions.  Therefore, ~1% ammonia in
methane is a better way to do ammonia CI.

Unfortunately, I don't have the references handy.  If you look 
back in Analytical Chemistry between, say 7 to 10 years ago
for an article in my name (Robert B. Cody) on low-pressure CI
with ammonia, you should find references to the original work by
Rudewicz and Munson that described the reasons for using ammonia
in methane as a reagent gas.  Alas, I don't seem to have the
article or the reference at my fingertips at this moment.  Maybe
Patrick or Burnaby could help if they are reading the newsgroup ?


		        	Sincerely		
	                        Robert B. Cody
		                Applications Manager
		                Mass Spectrometry
				JEOL USA, Inc.




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From: "David M. Parees" <pareesdm@ttown.apci.com>
Date: Wed, 10 Jul 1996 11:24:39 -0400 (EDT)
Subject: Re: STMS Mailing 

  I'm not sure what the problem is.  Did you contact Air Products and 
 Chemicals, Inc. (Allentown, PA)?  We got ammonia in methane mixtures from 
 them (I don't think the fact that I work for them has anything to do with 
 this).  Incidently, some investigators have also shown interesting 
 results for methylamine in methane; the most recent of this work was 
 Jim Little's (Eastman Chemical) at ASMS 1996.  Air Products does not 
 supply this, but we got it from Matheson (2% methylamine in methane; that 
 is also the type of ratio you want to use with the ammonia/methane 
 mixture, by the way).
 
     Dave Parees
     My company pays others to speak for it, therefore they will not 
    back up any comments that I make... 



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