SHADYCHASE54 - 9-10-2011 at 12:26
My question is whether reagents as well as solvents which have expired are still usable as is or if they must be repurified to fit proper standards?
Or is it that I am making a completely bogus assumption in thinking that they should ever be used at all? I suppose that it is fine to use them in
some cases as I have and have ended up with a fairly pure substances. So how could I determine which is okay and which should be sent off the the
waste center for processing. I am wondering about three chems. in particular thf, pyridine and acetic acid?
I will thank those of you in advance who might shed some light on this for me.
SHADYCHASE54
Oh yes this is completely unrelated however I was also wondering am I correct in assuming that this is a high pressure reactor? The thing is is I just
purchased this on the incase, as I have always wanted to explore high pressure reactions. If I am correct in assuming this is what I pray it is how
might I go about having it pressure/leak tested and later certified?
[Edited on 9-10-2011 by SHADYCHASE54]
ldanielrosa - 9-10-2011 at 13:45
This comes up from time to time. Manufacturers put an expiration date on everything to cover their a**es. Some reagents don't degrade, but some do.
Endimion17 - 9-10-2011 at 14:18
They have to put dates on literally everything because they guarantee that their product, stored properly, by the end of the noted time, will have not
more contaminants than they've wrote on the label.
In most cases, that's important for very sensitive analytical chemistry techniques. Covering their asses? You bet they are. I'd do it, too. 
SHADYCHASE54 - 9-10-2011 at 14:45
Thank you for your responces on the reagent solvent question. However, if anyone could offer up any thoughts on the vessel set I have purchased I
would also be very appreciative. Thanks again for your comments.
Shadychase54
fledarmus - 10-10-2011 at 03:59
Question 1 really depends on the solvent and the storage conditions. Ethers, especially if they have been opened or exposed to air, can form
peroxides. Not usually noticed until you decide to distill them off, and the peroxides dry out and explode. This includes diethyl ether (commonly just
called "ether"), tetrahydrofuran (THF) and 1,4-dioxane. Petroleum ether isn't an ether at all, it is just a low boiling alkane, so it can't form
peroxides.
Other than that, I don't know of any particular hazards with storing solvents other than slow decomposition. Distillation before use should be
sufficient to purify them if you really need it.
Question 2 - that system you show is actually an old Biotage flash chromatography purification system. You buy silica gel columns that fit either of
the two smaller tubes in the middle, put your solvent mixture in the big tank on the left, and use compressed nitrogen to force the solvent and the
compound you are purifying through the silica gel. I'm not sure what the object on the right is - it appears to be a larger column holder that
somebody has cut off.
Dr.Bob - 10-10-2011 at 06:54
1 - I agree with Fledarmus on that. The THF will eventually form peroxides if open. Having a trace of water will help lower that risk, but only
needed if opened already. Pyridine will last a long time, will absorb some water, but be OK otherwise. Acetic acid should last forever. We have
bottles that are years old that are fine.
There are some chemicals that really do get bad fast, organometallics, aldehydes, reactives like acid chlorides and isocyanates, and amines that can
air oxidize or form carbonates. But most acids, aromatics, and salts are quite stable. If the compound naturally reacts with moisture or air, it
will have a shelf life limit. But most others are fine. The system is only rated to 100 psi or so, I would guess, as it uses plastic fittings.
And the thing is a flash system, the right part may be for putting a small cartridge before the main column in order to load your sample. Google
biotage to look for the manuals and other info. I have some of those as well, somewhere, plus some other similar stuff. I'll look to see if I have
any loose columns for those.
Bob
fledarmus - 10-10-2011 at 07:51
Ah - took me a while, but I finally remembered the setup. That thing on the right is for using the large prep columns - they were made with a
luer-lock on the bottom and heavy-walled plastic that could take the pressure. They didn't need to be completely enclosed, just clamped sufficiently
at the top to keep it from opening up under pressure.
As I recall, we ran these at about 20-25 psi, not sure what they were rated for. Most people replaced the solvent reservoir/nitrogen system with a set
of liquid handling pumps as soon as they could afford it.
Dr.Bob - 11-10-2011 at 11:07
Yes, we usually ran the system at lower pressures 15-25 psi, but since the inquiry was about a high pressure reactor I wanted to make sure to note
that this is NOT a high pressure system as built.
Most people I know bought an ISCO system as soon as possible, which is a vast improvement. These did not work as well as most had hoped. But for a
hobbiest, it is a perfectly good flask system and removes the worry about glass vessels breaking and expensive pumps. These are fine for running
simple columns.
Bob
SHADYCHASE54 - 11-10-2011 at 17:23
Thank you all for your comments I shed a tear for this being a mere flash chromatography system, in my excitement I purchase it thinking I might use
it for hydrogenations. Maybe I can figure out how to modify it for my purposes otherwise there goes $124.00 including shipping down the toilette.
Dr.Bob - 12-10-2011 at 05:50
Shady,
If it helps, these systems used to cost over $1000 new, despite looking like something made of spare parts and junk. Biotage used to sell the
simplest things for an obscene amount of money. So I would learn how to do flash chromatography with it. It is still a good system for that.
Bob
jsc - 19-11-2011 at 18:25
This reminds of a conversation I had in college after I saw a friend of mine with a condom that had obviously been in his pocket for a LONG time:
Me: I bet that condom has reached its expiration date.
Him: Condoms don't have an expiration date.
I had a similar conversation with my ophamologist when I first got contact lenses.
Me: How long can I leave the lenses in saline solution?
Him: Forever.