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Last post I railed against microkits, pointing out that the majority of the reaction vessels don’t fit with standard lab equipment.  Then I started touting the advantages of small vials, which… don’t fit with standard lab equipment.  So, what gives?

The difference is specialization.  The glassware in a standard microkit has a mix of both ground glass joints and O-ring sealed threads, with each piece designed for a specific purpose.  This one piece for one job approach works really well in the controlled environment of an undergraduate laboratory, but leads to cupboards full of little-used glassware in a research setting.  As an example, I quite like using conical vial for microscale reactions (I did a lot of my undergraduate work using them with tiny spin vanes), but the thick glass and sloping walls make removing the solvent on a rotovap problematic, even if you have the custom-built threaded adaptor.  Conical vials also aren’t cheap, so it’s unlikely that you’re going to have a lot of them lying around when you want to run a half-dozen test reactions in parallel.

Being little more than small jars, 4 mL vials sit on the opposite end of the spectra, and can be used for half a hundred different things.  As a result, most of us likely have a box of one hundred vials nearby, and likely it was purchased in the last month or so.  Despite their interchangeable nature, these vials are built of relatively high quality glass, so they can be used with even your most valuable compounds (the quality seems to be comparable to most permanent glassware).  And unlike the threads of conical vials or the small ground glass joints, vials can be hooked up to almost anything, with a little work.

Following a generalized approach to glassware selection, I’ve found that only a few pieces of glassware are strictly required for the vast majority of reactions.  Basic reactions need a flask and a seal, a source of inert gas, and a stirrer.  Reactions run at reduced temperatures need a cold source (acetone/dry ice bath, etc), while those run at elevated temperatures need a heat source and a reflux condenser, which unfortunately can’t be reduced down to easily acquired components.  So the skills of a glassblower are required.

By sacrificing a few vials a simple reflux condenser can be built with relative ease.  The 13-425 threads of the vials take the place of ground glass joints, and standard glass tubes form the rest of the piece [1, 2].  This approach can also be used to convert your favourite microkit apparatus into something that can connect to a vial, though I imagine in most cases it’s more economical to build things de novo.

The missing link in the design is then a literal missing link, as something is needed to hold the thread of the vial to the thread of the apparatus.  It took fair bit of hunting, but I eventually found a source for 13-13 connectors, built with a PTFE bridge [3].  The one copy that our lab had on my arrival has withstood every solvent I’ve thought to throw at it, including a recent reaction that used stoichiometric amounts of elemental bromine at 80°C.


[1] I’m not the first to do the cut/join trick with vials.  It seems someone has had this idea before.

[2] Well, I’m assuming the rest of the apparatus is simple tubing.  I’m not a glassblower.

[3] These aren’t a perfect match to the image shown above, but they fit like a charm.  The manufacturers of the original connectors seem to have gone out of business long ago.