Schlenk lines are typically cleaned once or twice a year, or whenever they get contaminated. Teflon tapped Schlenk lines are significantly easier to clean since they should be free of grease, which can often be problematic for Schlenk lines with greased double oblique stopcocks. It is highly recommended to avoid soaking Schlenk lines with double oblique stopcocks in a base bath since the corrosive KOH/iPrOH solution can slowly etch the ground glass joints and compromise the seal. The methods and tips suggested below should be sufficient to remove grease and other contaminants from any Schlenk line.
Step 1: Carefully take down the Schlenk line from the lattice lab frame support and remove the tubing. It may be necessary to replace the tubing if it is too dirty to reuse. Alternatively, the tubing can be rinsed with water and acetone then dried in a warm oven, or simply recycled for another purpose.
Step 2: Support the Schlenk line in an upright position using a clamp stand and fill the vacuum manifold with warm toluene (or EtOAc) to cover the top stopcock. Due to safety concerns that have been raised, it is advised to avoid heating the solvent with a heatgun as the solvent vapors can easily be ignited leading to a fire.
Step 3: Allow the vacuum manifold to soak in the warm solvent for 15-60 minutes. Repeat this process as necessary, replacing with fresh warm solvent if needed, and then discard the solvent in an appropriate waste container once cooled to room temperature.
Step 4: The next step is to remove the grease from the stopcocks. This is best achieved using tissue paper soaked in a hydrocarbon solvent such as DCM, EtOAc or toluene. It may be necessary to use tweezers to manipulate the soaked tissue to remove the grease from inside the female joints of the stopcocks on the Schlenk line, and pipe cleaners to remove the grease from inside the bore of the stopcock.
Step 5: The Schlenk line can now be rinsed with water and acetone. A rinse or soaking with aqueous acid can be used to help remove inorganic oxides. The Schlenk line is subsequently rinsed with deionised water and acetone, and then allowed to dry in air or a warm oven before reassembling.
Teflon taps can simply be wiped down with iPrOH and a Kimwipe. Acetone should be avoided as this can compromise the O-ring.
Cleaning Schlenk Flasks
After safely quenching and disposing of the contents in the Schlenk flask, the grease is completely removed from the ground glass of the stopcock, stopper and female joints (EtOAc or DCM soaked tissues work well). The Schlenk flask is thoroughly rinsed with deionised water and then soaked in a base bath (KOH/iPrOH) overnight. It is then rinsed thoroughly with deionised water and then soaked in an acid bath (dilute aqueous HCl) overnight. It is again rinsed thoroughly with deionised water and finally with acetone. The Schlenk flask is allowed to air dry and then placed in an oven prior to use.