Re: make PEG fly now!

Deborah A. Grimm, Ph.D. (dgrimm@mailhost.tcs.tulane.edu)
Thu, 19 Aug 1999 09:15:06 -0500

We are analyzing PEG in our lab. Basically, we make a 1%
soln by weight of the polymer in either MeOH or CHCL3. Then
we use a 10mg/ml solution of DHB (2,5-dihydroxybenzoic acid)
as matrix. I mix equal amounts of matrix and sample in a
micro centrifuge tube and then pipette the 0.5ul from the
mix. Doping with LiCl can help. I have not really looked at
PEG derivatives, but adding a significant number of acidic
sites would make it much more difficult to get the polymer
volatilized. Have you looked at negative ions?

Also, you don't specify the mass range. But I have seen
published spectra for PEG 20,000. I have been able to easily
see PEG 5,000. If you start looking at higher masses, and
you have the option on your MALDI, try the low mass
deflectors.

Debby

Deborah A. Grimm, Ph.D.
Organic Laboratory Manager
Coordinated Instrumentation Facility
605 Lindy Boggs Bldg
Tulane University
New Orleans, LA 70118
Phone: 504-865-5142
Fax: 504-865-6768
e-mail: dgrimm@mailhost.tcs.tulane.edu

-----Original Message-----
From: Gary Van Domselaar <gvd@redpoll.pharmacy.ualberta.ca>
To: Recipients of ABRF List <abrf@aecom.yu.edu>
Date: Wednesday, August 18, 1999 8:33 PM
Subject: make PEG fly now!

ABRFers,

I am trying to quantitate the molecular weight distribution
of PEG and PEG
derivatives (ie proprionic-acid peg) by MALDI tof analysis.
I have read a
paper by Williams et al. in Macromolecules (1996),
29:8144-8150 that
describes liquid-phase matrix methods to make this work, but
they also
report nice spectra using 5ul alpha-CHCA in CH3CN as
substrate and sat'd
sol'n of the same matrix in MeOH:H20:PEG in equal volume of
1mg/ml PEG. I
tried the a-CHCA approach, but cant seem to get it the PEG
to fly under
these conditions, and I have toyed around a bit with ratios
of analyte to
matrix but still no luck. I have had some helpful
suggestions from the
Genetics Institute that doping the matrix with CsCl or AgCl
may work (it
works for PS). Does anyone have a protocol for this method,
or know of
another sure-fire way to make my peg or peg-cooh fly?

Cheers,

--Gary
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
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Gary Van Domselaar gvd@redpoll.pharmacy.ualberta.ca
Faculty of Pharmacy Phone: (780) 492-4493
University of Alberta FAX: (780) 492-5305
Edmonton, Alberta, Canada