i am trying to analyse culture media by esi ms and keep getting a contamination peak (353.12 and 705.23 in particular). According to the ms people it is not a peptide or lipid because its spectrum is too simple. I have been looking at common contaminant tables (plasticizers etc) and the m/z associated with those contaminants, so far i have not seen my contaminant.
i have bought new media stocks and tested them only to find the same contaminant. The MilliQ water that the media is made up in does not have the contamination. we use a previously tested amount of BSA so that it doesn't block the signal of less abundant proteins and a previous researcher was getting this to work, but i don't know what has changed apart from me.
The attached spectra are (1) media with BSA, (2) milliQ and (3) media without BSA.
Thanks in advance for any suggestions
Edited by rachelg, 11 February 2010 - 04:24 PM.