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Lab Safety

Setup may make transferring tert -butyl lithium and other pyrophoric reagents safer

Simple pieces of equipment decrease the danger of moving small volumes of chemicals prone to igniting

by Bethany Halford
June 18, 2018

 

20180618lnp1-billedeopener.jpg
Credit: Anders T. Lindhardt
Handling pyrophoric reagents can be dangerous.

When chemists want to transfer a small amount of a pyrophoric reagent, such as tert-butyl lithium, they typically use a needle and syringe. But this protocol can be dangerous: One wrong move and the chemical could drip, or worse, squirt out of the needle and ignite. Chemists at Aarhus University have devised a simple setup and protocol that can make such transfers safer.

The setup consists of a sealed transfer vial made by fusing the tops of two crimp neck vials, a three-dimensional printed bottle cap that screws onto the bottle of pyrophoric reagent and holds the transfer vial, and a metal clip that secures the system so that it’s “hands free.”

To transfer the reagent once the setup is assembled, a chemist pushes a long needle through both crimp cap seals on the transfer vial (which is filled with inert gas) and then through the reagent bottle’s rubber seal. The chemist draws the required amount of reagent into the syringe and then withdraws the needle so that it is contained within the transfer vial. After removing the transfer vial from the 3-D printed bottle cap, the chemist places the transfer vial onto the reaction flask, pushes the needle through the transfer vial and through a septum on the reaction flask, and finally transfers the reagent (Org. Proc. Res. Dev. 2018, DOI: 10.1021/acs.oprd.8b00151).

Credit: Org. Process Res. Dev.
A simple set up makes transferring pyrophoric reagents safer.

Chemists Anders T. Lindhardt, Mogens Hinge, Martin B. Johansen, and glassblower Jens C. Kondrup devised the system in response to an undergraduate laboratory experiment that called for students to transfer tert-butyl lithium. Although senior scientists closely supervised the students while doing the transfer, Lindhardt says that safety was a major concern. So, after many iterations, they came up with this system, which was tested and evaluated by 60 undergraduates.

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Credit: Org. Proc. Res. Des.
The set-up developed by Aarhus University scientists for transferring pyrophoric reagents.

Xiao-Feng Wu at the Leibniz Institute for Catalysis points out that pyrophoric reagents like tert-butyl lithium are used on a daily basis in some research laboratories, even though their high air and moisture sensitivities can lead to serious accidents, particularly when used by chemists who are inexperienced at transferring such materials. “With this system, even high school students can enjoy the advantages of tert-butyl lithium,” he says.

Debbie M. Decker, safety manager for the chemistry department at the University of California, Davis, thinks that the setup may be useful for transferring small amounts of pyrophoric reagents via syringe. “I think this is an important technique for undergraduates to learn in a teaching environment, rather than in the research environment,” she says. “Teaching students the cannula technique may be more useful in a research setting.”

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Lindhardt agrees that a cannula setup is better for transferring large volumes of tert-butyl lithium and similar reagents. He says the goal of this work was to make “something simple that people could construct themselves.” Although the chemists enlisted a glassblower to make the transfer vial, they published vial schematics online with the paper, along with specifications for 3-D printing the bottle cap and an instructional video.


This article has been translated into Spanish by Divulgame.org and can be found here.

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Comments
Robert Reed (Mon Jun 18 13:59:47 EDT 2018)
Dear Sir:
I like the device and the fact that it reinforces the care and attention required when handling pyrophorics.
Unfortunately I personally despise rubber plunger tips on syringes. They swell upon contact with organic solvents, jam and lead to more problems. Polypropylene syringes or glass gas tight syringes would be safer. Even polypropylene syringes get "sticky" plungers if used twice. There is no substitute for a properly cared for glass syringe.
Thank you
Dr. Robert W. Reed
Inorganic and Organic Chemistry Lab Coordinator
Department of Chemistry, University of Guelph
Richard (Tue Jun 19 05:57:37 EDT 2018)
I like the idea as it is simple to realize and reusable. The only part that I didn't like was the injection into the reaction vessel, which again is quite dangerous given that the transfer vial could slip from the septum at any time. I think going all the way to make the same transfer vial holder for a septum-covered flask (e.g. with joint springs) wouldn't have been too much additional effort.

Another point is probably that safety should be focussed on a failsafe for syringe plungers to not pop out during accidental overloading or reaction-induced pressurization.
Shankar (Thu Jun 21 13:06:27 EDT 2018)
I thinks the cannula can be successfully used for those metalation that has end point (color change). A
John Kopasz (Wed Jun 20 17:41:24 EDT 2018)
I agree with the previous comment that a stop mechanism to prevent complete withdrawal of the syringe plunger should be used. The syringe plunger being fully withdrawn has led to some severe accidents when attempting to transfer pyrophoric materials by syringe. A stop mechanism to prevent that is inexpensive and should be used.
Konrad (Thu Jun 21 02:51:43 EDT 2018)
This looks like nice approach towards more safety on lab scale and reminds me back to my PhD study times. We did work a lot with organic lithium reagents, e.g. n-BuLi and tert-BuLi. As fas as I remember during the years we never had big issues with transfer of those reagents and we used lots of them. We always used syringe with steel needle for transfer, making sure that there is no delta in pressure between the bottle and the atmosphere, especially when the tert-BuLi was coming from the fridge where it normally was stored.
Overall, I think it is always good to improve the safety of a process. Safety is the most important topic in life.
Alan Levy (Thu Jun 21 11:29:33 EDT 2018)
I have used something similar for years. It consists of an approximately 1" piece of 9 mm medium walled tubing with appropriate rubber septum's on each end. Note that the ends of the tubing should be fire polished before use. Stick a nitrogen or argon source and a vent needle into the septum's to clear the air. The septum's are a tight fit and can be tied down with copper wire. A nitrogen filled syringe with luer-lok and appropriate length needle are inserted into the glass tubing and the tubing butted up against the bottle. The needle is inserted through the septum's and filled. The syringe plunger is withdrawn to clear the needle and the needle withdrawn into the tubing. From there the procedure is similar to the video.

Because the septum's are compressed into the tubing and stretched over the outer wall, the vial has never slipped off the needle in my experience.
Shankar (Thu Jun 21 13:04:39 EDT 2018)
Regarding the statement by Xiao-Feng Wu of Leibniz Institute for Catalysis “With this system, even high school students can enjoy the advantages of tert-butyl lithium.” I hope he is not serious as these are still deadly agents that can cause immense damage from "playful" high school students.
Anthony (Tue Jun 26 10:19:33 EDT 2018)
Hasn't this method been around for a long time?

From Wikipedia: While handling pyrophoric material (e.g. tert-butyllithium and trimethylaluminum), traces of the compound at the tip of the needle or cannula may catch fire, and cause a clog. Some workers prefer to contain the tip of the needle or cannula in a short glass tube flushed with an inert gas, and sealed via two septa.[Errington, R. M. (1997). Advanced practical inorganic and metalorganic chemistry (Google Books excerpt). London: Blackie Academic & Professional. pp. 42–48. ISBN 0-7514-0225-7]

Instead of exposing the needle tip to the air, it is withdrawn into the inerted tube. Where desired, it may be inserted into a flask via two septa (one on the tube, one on the flask). Used this way, needle tip fires are eliminated, reducing the obvious hazards. Also, there is a reduced tendency for the needle tip to clog due to the reaction of traces of the reagent with air to give salts.

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