6/10/2007

"how many frits have you ruined?"

Sadly, this may be the last carbon-based photo you see from me for the next two months. I'm interning in a non-synthetic environment (as opposed to A Synthetic Environment?), so I won't have nearly as many colourful organic things to show you. I may throw up some device pics, though, since that's what I'll be doing in the meantime. While I could dig up some glowing liquids I've made and not posted, or some glowing TLC plates, I figure you might be more interested in what exactly I'm doing with some of the lovely materials we've blogged about here. That, and lit posts. No one ever gets tired of lit posts, right?


Anyway, the title question is something a labmate asked when she heard I was working on a particularly insoluble class of compounds. The answer was somewhere around three or four when I finally decided to do some cleaning because I needed usable glassware.

The pic on the left shows some pretty-but-insoluble gunk embedded in a frit. This isn't good. After repeated solvent rinses, nothing would come out. That is...until I went crazy and decided that sulfuric acid was really a pretty good solvent. Plus, it turns some things a lovely magenta-to-blue colour. NoChromix is also an option, so I've heard, as is a mixture of H2SO4 and H2O2.

Yeah, I know cleaning glassware isn't exactly exciting, but I bet yours doesn't turn bright pink. And neither will mine, for the next few months. Doesn't mean I'll stop writing, though.

15 comments:

Jean-Claude Bradley said...

That is how I learned the hard way to always put a filter paper over the sintered-glass :)

Ψ*Ψ said...

This is why I like blogging: So many people out there know more than I do. Nice of you to let me take advantage of your experience :)

milkshake said...

I found celite plugs the fritted funnels over time, so I have reserved few for that. Charcoal, Pd-C, Pt-C blacken them so filter this through celite pad. Ugly unwashable fritted funnels accumulate next to sink until I am brave enough to use sulfuric acid + H2O2. When I do I empty the hood as much as I can, put on double gloves, tut the sash down, make sure there are no organic solvents on the glassware or nearby or nothing flammable (paper!) and do the thing, let is slowly drip through overnight by which time the mixture has cooled and expired and is reasonably safe to take to the sink.

When I was working with very yellow and very insoluble oxindole kinase inhibitors, I used to go through this piranha mix routine every week until I got so frustrated that I spent about thousand bucks on fritted funnels. Boss compained when he found out - and that was about all he could do about it. Then I could go for few weeks without Buchner funnel washing.

jokerine said...

whats so bad about cleaning frits with acid? we do that all the time. first dilute HCl then HNO3 and then H2SO4 and then the concentrated acids. you get anyything out this way.

Anonymous said...

You can use aqua regia to remove Pd-C, Pt-C and other metal residues quite well. I use H2O2/H2SO4 with organic residues. Remove to flush with water to remove solvent residues first! Acetone forms triacetone peroxide with H2O2!

Charcoal can be removed by your friendly glassblower. He'll burn it off.

Where possible, I use celite in a pasteur pipette, plugged with a bit of tissue paper. Use and throw away. No frits to ruin.

dtb said...

You want to get yourself some filter units:

http://www.sohamscientific.co.uk/funit.html

basically, it's a 3-component frit - a lower bit made of glass (preferably with a vacuum adaptor and male ground glass joint), a perforated plastic disc, and an upper half that is basically a glass tube to hold the material being filtered. Clamp everything together, with two pieces of filter paper between the plastic disc and the upper half, then filter. There's nothing to block because the holes in the disc are very large.

Excimer said...

piranha (H2O2/H2SO4) is overkill for most organic chemists. The only advantage piranha has over no-chromix or chromic acid is it will hydroxylate surfaces, and if you're not in the market for that, then you don't need it. There are safer ways to destroy organics.

I was gonna do a post on piranha, but changed my mind. Maybe I will now?

milkshake said...

The reason I had to use piranha with those oxindoles was that they were phenomenaly potent in the bioassay - and at the same time I was working with some other compounds that were much less potent (but well-behaved and I was trying to improve their potency). Obviously I did not want to mess up my data because of some trace contamination.

Piranha is nasty and needs to be handled in open beakers that are much bigger than the mix volume as to provide for foaming-over, overheating etc.

A friend poured piranha onto a buchner funnel soaked in acetone and the funnel instantly detonated - he did not get hurt but had to use the emergency shower (stinky, cold, floods the lab) and his trousers got holes and his wallet and cell phone got wet. Not funny.

Excimer said...

yeah, it's nasty stuff. I use it on an (almost) daily basis- lucky me. Guess I will do a post on it next week.

Chemgeek said...

What about the inevitable dumping of a frit into a base bath by an unsuspecting lab rookie? Best way to convert a fine frit into an extra course frit.

Ψ*Ψ said...

Yeah, I have one frit that looks like that happened to it. I actually have yet to throw anything into the base bath (sometimes ours get really nasty). OCD glassware washing within a day of use takes care of most things, at least in my experience. If only I could force myself to do dishes that often...

milkshake said...

I know a guy who was actually unplugging Celite-ridden frits with a diluted HF. I guess the right timing is everything...

HetChem said...

H2SO4/H2O2 is one of my favorite wasing mixture, but for fritted-funnels blackened by palladium, I prefered HNO3 (this the first step to synthesize Pd(OAc)2 form Pd/C). But now, I almost always use celite or silica as pre-column.

Excimer said...

I always use no-chromix to get rid of palladium crap. works like a charm. Also great for getting rid of crappy polysiloxane residue from working up reactions with chlorosilanes.

Anonymous said...

Working with organometallic complexes I do the following:
- Aqua regia
- water
- NH3/H2O2

Works fine for me.