Which kind of samples? Which method are you using? ???

Hi,

thanks for you answer. I performed a cell lysis followed by an IP protocol. Then I run a precast gel...So polymers were not expected...When I run the sample after performing salt purification... I used a 30 min gradient on a Q-Exactive ... Unfortunately the sample was full of polymers that hampered the analysis

Not sure what you mean by polymers. Do you mean protein oligomers or non-protein polymers as chemical contaminants? Protein oligomers are generally a lot more likely.

unfortunately they are chemical contaminants sice they shos the classical shift of 44...so I think they are PEGs...

If it is PEG then the most likely source is residual detergents in the glassware.

http://www.proteomics.ox.ac.uk/documents/Mass%20Spectrometry%20Contaminants.pdf

This will cause a lot of other problems with many other assays as well. Rinse all the glassware out thoroughly and set aside one set to use for your protein purification. If this doesn't work, you can try a TiO2 microcolumn

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1949484/

which can be ordered from

http://www.newobjective.com/products/tools/prep.shtml

TiO2 will also absorb some proteins so try rinsing out the glassware first

This is not my own experience but, I heard from a mass spec expert that 1.5mL tubes from a certain brand can cause this type of contamination (i.e.contamination by chemical polymers). We normally use Eppendorf protein lo-binding tubes for preparation of MS samples and never had a problem of this sort.

Thanks a lot... I have already used Lobind eppendorf...I will read all the references and I will let you know...I was wondering if water could be contaminated...