Question: Rotors, End Caps, and Solvents
Chad M. Rienstra (RIENSTRA%SSNMR@CCNMR.MIT.EDU)
Tue, 20 Dec 94 08:47 EST
I have a question which perhaps someone with the proper experience
might be able to answer easily. It regards exposure of solid state
spinner parts to solvents for cleaning. In order to kill proteases
and other enzymes which might wreak havoc with sensitive biological
samples, it's necessary to clean things with dilute (10%) nitric acid
or a solution of potassium hydroxide in ethanol. How do these solvents
effect high speed MAS rotors made of zirconia, sapphire, and/or silicon
nitride and end caps made of Kel-F or vespel? I could certainly test
the sensitivity of each material by exposing them to the solvents, but
there are two reasons I don't want to do that: (1) At upwards of $300
per rotor and $75 per end cap, it would be a very expensive way to
uncover the potentially obvious; and (2) microscopic damage (most
likely etching in the case of HNO3) might be invisible to inspection
yet lead to serious problems down the line. In particular, fatigue
in the rotor might lead to unstable spinning at high speeds, or in
the worst case scenario, the rotor could explode, damaging the stator,
stator housing, and precious sample with it.
Chad