Cleaning of NMR Tubes
Tubes left with samples in them for a period of time frequently present a
challenging cleaning problem. Sample degradation or precipitation can cause
material to adhere to the inner walls of the tube. Rinsing the tube doesn't
always remove this adhered material. It's therefore often recommended using
strong mineral acids such a concentrated or, in severe cases, fuming Nitric
Acid soaks of 1-3 days, as needed. Nitric Acid can oxidize many organic
chemicals and dissolves most inorganic materials, as well. A final
rinse with distilled water or Acetone is also appropriate.
Tubes which contained polymeric samples can be even more difficult to clean.
When the polymers are natural products, like proteins and polysaccharides,
strong acid soaks will usually be sufficient. However, when dealing with
synthetic polymers, the challenge is more severe, since many polymers are
inert to acids or insoluble in organic solvents by design.
Although polymers may not readily dissolve in solvents, it may be possible
to soften them by soaking the tubes in a solvent that swells the polymer.
Then a pipe cleaner might be sufficient to remove the softened material. It
may take some experimentation to find the solvent combination that works
best with your polymer system.
Your Partner - for Aqueous Cleaning Solutions!
Researcher at Borer Chemie AG, Switzerland developed a
cleaning process particular for these special application. The whole
cleaning process inclusive drying of these delicate tubes will not take
longer than 90 minutes and can be made in any laboratory glassware washer
with at least two liquid dosing pumps. The tubes have to be placed in a
special jet rack to ensure sufficient water flow through the tubing.