Wash your hands ... or glass?

[natusik]

Have you ever mixed acetonitrile with water in 1:1 ratio and then shake biker (flask, bottle) vigorously? After I did it today I noticed extensive bubble formation (like a foam). Is it contamination from detergent-washed glassware, or it is supposed be like this? I used like a 3 different glassware, but always have this foam-like bubbles.

I have struggled with PEG contamination my MSQ Surveyor last two weeks and want to find out the source of contamination.

+44 m/z peaks appeared only when I used chloroform/methanol/NH4OH mobile phase (80/19.5/0.5). Methanol/water (50/50) or acetonitrile/water (50/50 w or w/o NH4OH) give fine clean background. Looks like chloroform/methanol combination extracted something from somewhere.

Thanks for any idea.

I changed tubing (now I am using direct infusion, not LC). So, contamination is in the solvent-pump-mass-spec part.

[Kostas Petritis]

It would be best to use new glassware to prepare your mobile phase if you think that you might have contamination from washing them (you always contaminate your glassware if you use detergent to wash them).