This basic style washer is an economical, convenient, and effective way to clean NMR sample tubes. Insert the washer body into a vacuum flask, invert the sample tube over the central capillary, and secure it in place with a modified tube cap. When a vacuum is applied and the reservoir is filled with solvent, a spray of solvent washes the tube and is collected in the flask. Several solvents may be used in sequence followed by an “air rinse” to dry the tube.
Available with a straight body or with a 24/40 inner joint. The reservoir capacity is 8ml.
It is important to understand that NMR sample tubes are NOT laboratory glassware and should not be treated as such. Because of the precision tolerances and the very thin wall weights, conditions suitable for labware will adversely affect these tubes. If one is not overly concerned with cross-contamination, NMR tubes may be soaked in a mild cleaning solution and rinsed with deionized water. Follow this with a rinse of clean methanol or acetone, after which they may be air dried. A basic tube washer, such as shown here, will help with this procedure. If moisture presents a problem, the tubes may be placed in a vacuum oven on a very flat surface (never standing and only in one layer). Heating should not exceed 100°C and one hour duration. When dried, cap and store the tubes in a desiccator.
For samples that are most difficult to remove, it is safer and more efficient to avoid radical and extensive cleaning methods - use of strong acids, etc.. Discard the tube and avoid cross-contamination. This is most practical when standard 5mm tubes are used.