Sealing Effect of Magic-Angle-Spinning Rotors in Solid-State NMR

Abstract

Several methods are proposed to check the sealing of a magic-angle-spinning (MAS) rotor. The intrusion of moisture into the MAS rotor is checked by trimethylphosphine oxide, which is highly hygroscopic. Its hydrated form is separately observed in ³¹P MAS NMR spectra from the crystalline (anhydrous) form. ¹H MAS NMR can monitor the hydrated form, the crystalline form, and adsorbed water independently. Gas leakage from the MAS rotor is monitored by measuring ¹²⁹Xe MAS NMR spectra of xenon (Xe) confined in zeolites as well as ³He MAS NMR spectra of ³He gas. The sealing effect of MAS rotors has been checked quantitatively using the above methods.