Design of solenoidal microcoils for high-resolution 13C NMR spectroscopy

Typical high-resolution natural-abundance C-13 NMR experiments require milligrams of material. In this study, solenoidal microcoil direct and inverse detection probes have been designed to explore improvements in the limits of detection (LOD) for C-13 NMR at 11.7 T. A direct-detection radio frequency probe with an observe volume (V-obs) Of 1 mu L has been developed with carbon observe, deuterium lock, and proton decouple channels. The nonspinning line width of a decoupled [3-C-13]-L-alanine (99%) peak achieved is 1.3 Hz. The natural-abundance C-13 3 sigma LOD for sucrose for a 90-min acquisition time is 18 mu g (52 mnol), The 3 sigma LOD for [3-13C]-L-alanine (99%) is 375 ng (4.2 mnol) for an acquisition time less than 30 s. The inverse detection probe has proton observe and carbon decouple channels and a V-obs Of 550 nL. The 3 sigma LOD for sucrose from a 1D C-13 decoupled HMQC spectrum is 1.6 mu g (4.5 nmol) for a 14-min acquisition time.