Jyllian,

For transfer of pyrophoric reagents, the method described in the OPRD paper has been around for quite a while in various forms. The key point is protecting what is potentially a needle full of pyrophoric reagent that may drip. Hence the inert gas transfer tube.

I teach my students an alternative method that has two small and easy techniques with significant benefits. In the OPRD paper and the UCSD video notice that they use a short, straight needle. That creates two problems 1) how do you get the gas bubble out of the syringe when measuring out the reagent? And 2) when you remove the needle from the reagent bottle gravity will pull the pyrophoric reagent out of the needle, especially since the solvents used have no surface tension.

So the first technique I teach is to use a long (12-18") needle bent in a U shape, rather than merely straight. (22-24 gauge for small volumes and 16-18 gauge for larger volumes.) That way the tip of the syringe is pointed up so it is trivial to remove gas bubbles and measure out the proper amount of reagent.

The second technique is to draw a plug of inert gas into the syringe after measuring out the reagent. That removes pyrophoric reagent from the needle to prevent flaming drips and thus eliminates the need for the separate inert gas transfer tube.

Specifically, all of the following are done with the syringe tip pointed up: 1) purge syringe with inert gas, 2) draw a small excess of reagent into the syringe through the long U shaped needle, 3) push out gas bubbles and excess reagent back into the bottle leaving a carefully measured amount of reagent in the syringe, 4) raise needle tip above liquid level but still in the bottle, 5) draw an inert gas plug into the syringe thus clearing the needle of pyrophoric reagent, 6) pull needle out of bottle and insert through septum of reaction flask, 7) deliver inert gas plug followed by measured amount of reagent to the reaction flask.

That carefully transfers the measured amount of reagent to the reaction, but what about what is left in the syringe needle? Pumping the syringe plunger is wrong as that would add an unmeasured amount of reagent. So after step 7 above and still keeping the syringe tip pointed up: 8) Draw an inert glass plug from the reaction flask into the syringe thus again clearing the needle of any pyrophoric reagent, 9) remove needle from reaction flask and insert into flask of inert rinse solvent for cleaning.

I made a video early on in my journey to improve lab safety and it is here. (Early on so maybe not perfect.) The two techniques I describe here are at 5:11 to 6:55 in the video. (The purge step 1 is at 5:11-5:27, loading steps 2 and 3 are at 5:31-6:12, creating the inert gas plug step 5 is at 6:14-6:22, and step 8 is at 6:53. )

https://www.youtube.com/watch?v=21iC4YEgOAs

I hope this is useful.

Best,

Craig

Craig A. Merlic

Hi Jyllian,

I've looked at both, and I think Neal's comments are spot on. This procedure is fine for small volumes, and is reasonable for a teaching lab scenario where, say microscale procedures are in place. If the lab is designed to teach applications that might occur for practicing chemists and larger volumes, learning good cannula skills might be more important.

Dom Casadonte

Jyllian

The device will perform well for 1 mL titrations and perhaps up to 10 mL reactions, beyond that it will be difficult to use and offer no advantage over a canula.

The device will require some practice to learn to use and careful attention to proper procedure - that is to say, it will need operator training.

Finally, it has an equipment barrier to use that a lab will need to commit to overcoming.

Bottom line - I see an incremental advantage for small scale pyrophor use.  For the application described - a teaching lab, it does make sense.

Thanks for bringing this to our attention.

Neal

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From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU> On Behalf Of Jyllian Kemsley
Sent: Tuesday, June 12, 2018 7:06 AM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: [DCHAS-L] New procedure for transferring tert-butyllithium from Sure/Seal bottles

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