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).
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.
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.”
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.