Chromatography Forum

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

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