> Hong Li,
>
> I have seen a series of peaks that differ by 44 when I was running
> nanospray. The samples I ran ( >2mL) were concentrated / desalted on a
> C-18 micro concentrator ( <2uL resin) and eluted with 10 uL of 50% ACN,
> 0.1% formic acid. I found that the water I diluted my samples with had
> trace amounts of this delta 44 material that concentrated on the C-18.
> Totally swamped my mass spectra at times. I switched to B+J water and the
> peaks went away. I never identified the contaminant.
>
> Mike Knierman
> knierman@lilly.com
>
> >This might have been discussed before, what are the common polymers,
> >detergents or plasticizers that show up in ESI spectra as series of
> >polymers differ by 44 amu? If not detergents, can these materials be
> >bleeds from tubes, columns, capillary or concentrator membranes?
> >
> >Hong Li
> >
> >
>
The delta 44 mass appears on detergents carrying polyoxyethylene
groups (O-CH2-CH2)n (16+4x1+2x12=44) such as tween, tritons etc.
Sources of this type of contaminats are typically detergens used in
previous manipulations of the protein of interest, or contaminated
glassware. Also a RP column contaminated with detergent may leak out
enough detergent to be seen on the mass spec for weeks.
We have also observed that some plasticware can leak this kind of
"detergentlike" stuff. This contamination is likely to be due to
chemichals used in detaching the plasticware from their molds after
casting.
Juhani Saarinen
Protein Chemistry Laboratory
Institute of Biotechnology
University of Helsinki, Finland
e-mail jksaarin@operoni.helsinki.fi
Phone +358-9-708 59 414
Fax +358-9-708 59 416
Street adress:
Viikinkaari 9
FIN-00014, Helsingin yliopisto
PL 56