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From: singley@clinpharm.niaaa.nih.gov (Erick Singley)
Subject: Humidity and derivitization
Organization: (National Institutes of Health, Bethesda, MD)
Date: Thu, 27 Jul 1995 15:44:42 GMT

Background: I've got a HP 5970 with a Phasor HED running Chemstation (windows)
and a 5890 GC with a J&W Scientific DB-225 (50% Cyanopropylophenyl) Methyl-
polysiloxane.

Problem: I"m extracting neurotransmitters (5-HIAA; MHPG; HVA, etc) from
cerebral spinal fluid (acid/base extraction with ethyl acetate), drying, and
derivitising with TFAA and TFE. Everything *was* going all right, but I've got
a rather dramtic drop in peak hights with our SIM scans.  People here say
it's a humidity problem (45%) wrecking my anhydrous reaction.  (Maryland
in the summer...) Has anyone else had a problem with esterfication or
anyhydrous derivitisation in the summer more than the winter? 
What humidity level should I be comfortable with trying again?

I've replaced all my reagents with new (blew nitrogen into bottles to displace
moisture laden air); retuned the MS; and tried running the same samples on
someone else's GC/MS (similar set up) - same results (so I don't think it's
my instrument. no air leaks)

I can always try doing a prep in a cold room here and then trying it, say,
outisde where it's really rotten :) but I' thought I'd ask around to see before
I start wrecking any more samples (bit hard to ask for more CSF after the study
is done...)
Thanks
Erick
--
singley@clinpharm.niaaa.nih.gov


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From: rjnemery@uniwa.uwa.edu.au (Neil Emery)
Subject: Re: Humidity and derivitization
Date: 2 Aug 1995 09:36:29 GMT
Organization: The University of Western Australia

In article <3v8iqv$cma@acmex.gatech.edu>, singley@clinpharm.niaaa.nih.gov (Erick Singley) says:


I assume you've tried cleaning the ion source although you didn't mention it 
in your message.

I've had problems getting rid of water when I make TMS derivatives, and try to 
get around this by adding methylene chloride as an azeotrope and evaporating under a stream of N2
I don't have any experience with TFAA/TFE, but perhaps my comments might help, as noone else appears 
to be answering.  If they are I'd appreciate seeing the responses posted, since I think the problem
is of general appeal.

Neil