m/z 254 and m/z 300-500 contamination

[areeya]

I found out the contamination ion intensify at m/z 254 and many ion between m/z 300 - 500. These can be observed even no injection. I used H2O+Formic acid+ammonium acetate and Acetonitrile for mobile phase.

I changed mobile phase to only MilliQ water and Acetonitrile, however, these ions still can be observed. I used gradient mode. These ions are always observed in period of acetonitrile.

Are there anyone had the same experience or any suggestion to clear up these contaminant?

Thank you,
Areeya

[sassman]

What grade solvent are you using. We have found that it is necessary to use a very high grade solvent to avoid seeing these kinds of problems. A bit more expensive, but should solve your problem. Alternatively, you can distill your solvents prior to use (preferably multiple distillations). Or just try chromasolv from Sigma-Aldrich:

Part number= 34967-2.5L