Cleaning NMR Tubes Prior to Use or Reuse

Whenever we use a tube—even for the first time—we may wish to wash it out thoroughly. If rinsing with appropriate solvents fails to properly clean an NMR tube, the tube may not be visually free of residue. That is, it will appear cloudy or translucent instead of transparent. Immersion of the tube for 30 seconds in a saturated base and alcohol bath may suffice. Caution when we perform this step, we wear gloves, a laboratory coat or an apron, and safety glasses or a face shield—we are only born with, after all, one perfect suit of skin and one set of eyes, hands, and feet. 

Sometimes physical abrasion is needed to properly clean a tube. In this case, we GENTLY scrub the inside and outside of the tube. We can use pipe cleaners to clean 5 mm NMR tubes effectively, but we must take care not to scratch the inside of our tube rvith the exposed wire at the end. 

We may even have access to an NMR tube washer, a device available from vendors of chemical laboratory equipment. If possible, we use high-performance liquid chromatography (HPLC) or spectroscopy ( Spec ) grade water or acetone for the final rinse. We never use dimethyl sulfoxide (DMSO) for the final rinse unless we are immediately going to reconstitute our sample in DMSO, because the low vapor pressure of DMSO prevents its evaporation. Caution we always wear gloves when working with DMSO. If our solute/DMSO solution comes in contact with our skin, the DMSO will transport our solute direcdy through our skin into our bloodstream. 

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