Chromatography Forum

We use parafilm extensively throughout our lab. we are seeing erratic retention times and basline drifts. Our mobile Phases are mainly buffered solutions without organics, however our needle rinse and seal wash are 90% methanol to water.
has anyone seen parafilm as a source of these problems? What do you guys use? Aluminum foil? bottletop caps with multiple holes?

parafilm is only of concern if it is on the mobile phases w/ organic solvents right?

Hi semivoadude,

First thing first: What makes you think that the parafilm causes the erratic retention times and the baseline drift? Have you reached to this conclusion through experiments or is it just a thought?
We use bottletop caps with holes in our lab but the reason for that is the ease of use.
So, unless you can eliminate the problems mentioned above by substituting the parafilm with something else, you have nothing to fear, according to my experience anyway.

90% methanol in water as needle rinse and seal wash can potentially cause a problem bearing in mind that your mobile phase is some kind of buffer (maybe highly concentrated) but I won’t bet my savings on this one

Best Regards

I'd say parafilm is an unlikely source of contamination. Most of the time you just use it to cover up mobile phase bottle right? You can always change the cover to aluminium foil and see if the baseline drift issue still arise.

If you are using a largely buffered MP, I think you should change your seal wash to 90:10 H2O:MeOH/ACN. Seal wash mainly serve to remove buffer deposit so a higher aqueous medium is more suitable. Needle wash shouldn't cause too much disruption to your chromatogram because I think it only wash the outside of the needle (well for Waters Alliance anyways).

Dear semivoadude:
We never experience contamination by parafilm (we use it to cover the diluted samples). For MP with organics, we use caps called "Vaplock" (you may buy from Chromtech.com).
Do you have a column heater?
Alfred

Hi,

My concern with parafilm is if you seal the bottles too tight and do not leave a vent hole. As you use mobile phase, you could create a partial vacuum. That would “starve the pumpâ€

Just a quick comment about the Seal Wash solution :

I was wiping by lab bench with 70% ETOH and could not clean up some spots of dried salts from buffer. Swiched to water and it cleaned up easily.

This got me thinking about using strong solvent for a "pump head seal wash" when using aqueous buffers ... not a good idea !