http://www-east.elsevier.com/webjam/access/fast-toc.htm.
"Sodium Trifluoroacetate as a Tune/Calibration Compound for Positive- and
Negative-ion
Electrospray Ionization Mass Spectrometry in the Mass Range of 100-4000 Da,
M. Moini, et al, on-line June 25, 1998.
It appears that there IS some truth to the old saying "one man's trash is
another
man's treasure."
At 09:37 AM 7/21/98 -0500, you wrote:
> We have also observed a series of ions separated by 136 amu by
>Electrospray MS. This series of ions appeared to be Na trifluoroacetate
>clusters with the first ion of the series at 159 amu [ie., (Na
>trifluoroacetate)+Na+] and subsequent ions at 295, 431, 567, 703, and
>so on. The sample in which these clusters appeared was a peptide
>isolated by typical reverse phase HPLC with TFA/Acetonitrile containing
>solvents. The customer had decided to neutralize the peptide fraction
>with NaOH solution prior to drying the fraction. We verified the source
>of the cluster ions simply by mixing TFA and NaOH solutions, diluting
>the mixture with our usual solvent for ESMS analysis of samples
>introduced by infusion, and checking the result by ESMS.Further
>comments:
> Sources of sodium in samples for MS need not be as obvious as the
>one above. A sample may contain a large concentration of a sodium
>salt. On HPLC, the tailing of the sodium salt may be collected along
>with the peptide of interest and then be concentrated along with the
>peptide.
>
> Sodium ions may arise from poor quality water used for preparing
>HPLC solvents, contaminated glassware, alkaline reagents stored in glass
>bottles.
>
> An example: In our laboratory a simple tripeptide with only the
>c-terminal COOH available for ionization is solubilized in ammonium
>bicarbonate solution, then diluted with 50% methanol containing 0.5%
>acetic acid for positive ion ESMS analysis. If the ammonium bicarbonate
>solution has been prepared and stored in plastic containers, the peptide
>spectrum shows the M+H+ and M+NH4+ ions. However, if the ammonium
>bicarbonate solution has been prepared and stored in glass containers,
>the peptide spectrum has a high proportion of sodium and potassium
>adducts.
>
>Beverly DaGue
>Research Associate
>Analytical Chemistry Center
>University of Texas Medical School
>Houston, Texas 77225
>(713-500-6285)
>bdague@bmb.med.uth.tmc.edu
> Len Packman wrote:
>
>> I have some sample contamination on mass spec analysis which appears
>> as a
>> polymer with a repeat unit of 136Da. Any ideas as to the nature of
>> this? Is
>> this another 'releasing agent' problem from the tube manufacture? All
>> samples are ingel digests which have been prepared using the Keck
>> Facility
>> protocol and then cleaned up on a micro C8 cartridge.
>>
>> Thanks for any input
>>
>> Len
>>
>> *********************************************************************
>> Dr Len C. Packman
>> Assistant Director of Research
>> Protein and Nucleic Acid Chemistry Facility
>> Department of Biochemistry
>> University of Cambridge
>> 80 Tennis Court Road
>> Old Addenbrookes Site
>> Cambridge, CB2 1GA, UK
>> Tel: +44 (1223) 333639 (including answerphone)
>> FAX: +44 (1223) 766002
>> e-mail: lcp2@mole.bio.cam.ac.uk
>> Visit my WWW page at http://www.bio.cam.ac.uk/proj/adr/PNAC/pnac.html
>
>
>
>
______________________________
Dan Kirby
Harvard University
Microchemistry Facility
16 Divinity Av Cambridge MA 02138
617.495.4043 fx 617.495.1374
http://golgi.harvard.edu/microchem
dkirby@fas.harvard.edu