Syringes and Sure Seals

Recommended reading: Safe Handling of Cannulas and Needles

Many air and moisture sensitive reagents or anhydrous solvents that are commercially available are stored under an inert gas and sealed with a rubber septum to maintain their purity during long-term storage and use. Removing the liquid from these sealed vessels requires inert gas to be flowing to re-equalise the pressure. This prevents a reduction in pressure (partial vacuum) sucking air (and moisture) in through the damaged seal which will degrade the contents.

Step 1: Insert a clean needle into the Schlenk line tubing using an appropriate screw-thread adapter and hose clamp/jubilee clip to secure it in place. Purge the needle and tubing by passing inert gas through it for 30+ seconds. Clamp the reagent/solvent bottle and tubing in place.

Purging a gas inlet needle.

Step 2: Unscrew the cap from the reagent bottle and remove the protective sheath from the needle and pierce the needle through the rubber septum.

Inserting the gas inlet needle through the rubber septum.

Step 3: Purge a syringe and needle by piercing the septum and inserting the needle into the headspace of the reagent bottle. Withdraw inert gas into the syringe and then remove the needle from the septum and expel the inert gas. Repeat this process two more times.

Purging a needle and syringe with inert gas.

Step 4: a) Re-insert the syringe/needle through the septum down into the body of the liquid. b) Slowly pull the plunger to withdraw the liquid into the syringe, removing slightly more liquid than required. c) With the needle still pierced through the septum, carefully bend the needle and turn the syringe vertically, then depress the plunger to remove the gas bubble. d) Continue depressing the plunger until the desired volume of liquid has been reached. Note: It may also be desirable to withdraw a small pocket of inert gas into the syringe to protect the reagent or solvent from exposure to the atmosphere during transfer.

Withdrawing liquid from the sealed vessel.

Step 5: Carefully remove the syringe and needle from the reagent/solvent bottle and pierce into the reaction flask. Slowly depress the plunger to expel the liquids. Remove the needle and syringe and dispose into an appropriate sharps container. For pyrophoric reagents it may be necessary to quench any residual material in the syringe with toluene/IPA prior to disposal.

Adding the liquid to the reaction flask.

Step 6: Remove the inert gas inlet needle from the reagent/solvent bottle and replace the screw cap.

For frequently used reagents such as ⁿBuLi, it is advised to decant the contents from the bottle into an ampoule with a Teflon tap via Cannula Transfer since the rubber septa are prone to leaking after repeated use. When large amounts (>20 mL) of reagent from a sure seal bottle are required, it is recommended to cannula transfer the liquid into a graduated dropping funnel.

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