Magic angle coil spinning

A. Wong, X. Li, D. SakeUariou, Refined magic-angle coil spinning resonator for nanoliter NMR spectroscopy enhanced spectral resolution. Anal. Chem. 85 (2013) 2021. 

Wong, A., Bonhomme, C., Sakellariou, D., Korvink, J.G., and Wallrabe, U. (2012) Microfabricated inserts for magic angle coil spinning (MACS) wireless NMR spectroscopy. PLoS One, 7, e42848. 

Figure 1. Schematic drawing of a magic-angle spinning device. The Kel-F sample holder screws into a rotor base that is then loaded through the top of the coil. The stator is fixed and the spacing between the pole faces of the iron magnet is 25 mm other dimensions are to scale. Spinning speeds of 2 kHz can be achieved with 20 psi pressures and unfluted rotors, and over 3 kHz with fluted rotors. The sample volume is 420 fiL.

One further approach to miniaturisation in the Varian NanoProbe has been the use of small rotors of 40 pL total volume inside the specially constructed probe head that spins the sample at the magic angle (54.7° from the axis of the Bq field) at severtd kilohertz to eliminate lineshape distortions that would arise from sample discontinuities close to or within the rf coil (magic angle spinning is described in Section 10.7). This allows the whole sample volume to be retained within the coil s active volume, unlike tube-based approaches where up to 50% of the sample may sit outside of this volume, and so improves sensitivity. The use of MAS also makes the probe suitable for the analysis of heterogeneous samples such as those attached to resins from combinatorial synthesis [32], but it lacks the convenience of tube-based sample handling and appears to be less widely adopted for work with mass-limited samples. 

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