Mass Contaminat ions Help

[CoCo]

I am seeing two contaminat ions on LC-MS, 227.2 and 453.2. It's the ABI QTrap 2000, EMS positive scan mode. Mobile phase containg water, acetonitrile and formic acid, ammonium formate.

I suspect these ions are plasticizers, but I didn't filter the mobile phase. Any boby know waht these ions are and what could be the contamiant scouce?

Thank you.

[jag]

I am not sure about 227.2, but 453.2 is a palsticizer. I also got 453.2 when I used formic acid packed in plastic bottle. It is known to be the adduct of diisooctyl phathalte with sodium and acetonitrile (Diisooctyl phthalate+Na+CH3CN).

If any one of reagent used for mobile phase is packed in plastic container then you may get this ion even if you don't filter the mobile phase.

[CoCo]

Tahnk you, Jag.

I did use formic acid packed in plastic bottle. So that's the problem. I also used water purified through a water system, the 227.2 could come from the water.

Thank you for replying my post.