A sealed MAS rotor insert for liquid and air-sensitive samples

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

“…Xenon gas contained 129 Xe with the natural abundance (26.4%). 3 He gas was obtained from Isotec Inc. (Miamisburg, USA), whose purity was at least 99.95 atom%.…”

“…Those samples might react with H2O and O2 in the driving gas during measurements, because MAS rotors cannot prevent the intrusion of the outer atmosphere completely. In order to measure MAS NMR spectra of moisture-and air-sensitive materials, several techniques have been proposed: a magic-angle spinner for vacuum-sealed glass samples, 1,2 a sealed MAS rotor insert made of polychlorotrifluoroethylene (Kel-F), 3 an O-ring end-plug, 4 a glass insert sealed after packing the sample, 5 and so on. The use of inert gases, such as N2 and He, as a driving gas instead of compressed air also protects any sensitive materials, but the consumed gas is expensive.…”

“…The pressure dependence of the 129 Xe shift was measured at room temperature with a Bruker ASX400 spectrometer, using a Bruker probehead for a solution with a sample tube having a 10-mm diameter. A special sample tube was used, which was similar to that previously used for 3 He NMR measurements, 8 but the inner tube was not necessary. The sample tube was connected with a system of evacuation and gas supply through an adapter and a 1/8-inch plastic tube, which was also similar to that used for 3 He NMR measurements.…”

“…A special sample tube was used, which was similar to that previously used for 3 He NMR measurements, 8 but the inner tube was not necessary. The sample tube was connected with a system of evacuation and gas supply through an adapter and a 1/8-inch plastic tube, which was also similar to that used for 3 He NMR measurements. 8 3 He MAS NMR spectra were measured at room temperature with a Bruker ASX200 spectrometer at 152.…”

“…1 H MAS NMR can monitor the hydrated form, the crystalline form, and adsorbed water independently. Gas leakage from the MAS rotor is monitored by measuring 129 Xe MAS NMR spectra of xenon (Xe) confined in zeolites as well as 3 He MAS NMR spectra of 3 He gas. The sealing effect of MAS rotors has been checked quantitatively using the above methods.…”