Chromatography Forum

Hi,

I have a lot of volumetric glass which has a crappy meniscus. I'm in a new lab and my mates say they used corning vacuum grease on some of the glass and there seems to be a film on a lot of glass. It causes the water to bead up a lot and the meniscus is flat and not concave.

I tried soaking in high conc alconox. Now I'm soaking in hexanes. After soaking for 3 hours and rinsing with IPA, Acetone, water there is no improvement.

Has anyone experienced this before?

Maybe someone in the lab has been using siliconising agents (like Sigmacote)??

That stuff is impossible to remove from glass, and destroys the meniscus.

Soaking or sonicating in a strong base will probably take it off, but will also cloud the glass. I recommend new glass and hiding it from @#$%&s.

I agree with Don !

Its funny, as a uni student back in the day I did a project on polarography, the lecturer had me cleaning the glass with 10% solutions of HF (!).

Certainly wouldn't do it now but it got the glass clean...

Ha. Like brushing with wire bristles isn't it?

If the contaminant is Corning silicone vacuum grease you can try a saturated solution of KOH in isopropylalcohol.
Chloroform or hot decaline are also usueful to remove silicone grease.

Robert

There comes a point when the cost of new glassware is lower than the cost of chemicals and time to clean the old glassware. If your bean counters protest, then gravity and a tiled floor are your friends.

Peter

Glacial Acetic Acid works wonders and is not that expensive.

Dawn kitchen soap will also work wonders as a pre-soak before the acetic acid.

best wishes,

Rod

If you are as busy and understaffed as most chemists, nothing beats the Peter Apps approach.

At least recycle the glassware instead of putting into the town dump.

They can be made into decorative pieces when filled with colored water.



Or can be used as small vases for flowers.

Rod

Great suggestions. Haha. I have found that rinsing with hexanes get rid of the thick layer of dimethicone grease that might be there but it's not enough to remove the film that ruins the meniscus. Soaking in ~30% nitric acid definitely does the trick without harming the glass. It smells bad but works. 10% nitric acid also works but it takes longer.

The only other thing that works was breaking the glass and starting over as mentioned above. I like the acid bath

The acid bath will remove the vwr labels and graduations on beakers, however.....

...take the good with the bad I guess.

MEK/cyclohexanone is also one of the cleaning agent for high vacuum grease

Damn floors !