I have had success in the past with negative ion ESI, using both LC-MS (up
to 0.7 mL/min without flow splitting) and syringe pump infusion, and it was
actually easy to set up. I just followed the user's manual instructions for
tuning at high flow rates (this was on a TSQ7000), using peptides of known
(M-H)-, looking at both positive and negative ion modes. I must also
confess that, at times when I was either too hurried or too lazy to do this,
the autotune in positive ion mode provided for acceptable negative ion mode
tuning. My LC mobile phases were the standard 0.1% TFA +/- ACN, which
suited me fine since I wasn't sample-limited; if you need to boost the
sensitivity, acetic and formic acid should be suitable replacements.
Mike Klein
Amgen, Inc.
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From: Dougie Lamont [SMTP:dougie01@globalnet.co.uk]
Sent: Wednesday, July 21, 1999 12:56 PM
To: Recipients of ABRF List
Subject: ESI-MS in negative ion mode
Hi all,
I'm interested in analysing acidic peptides in negative ion mode.
Has anyone done this type of work and could provide some information on the
best method of analysis (online-LCMS or infusion),buffers etc.
Thanks
Dougie Lamont
PPL Therapeutics