While being extremely versatile, NMR has the inherent challenge of being insensitive. One strategy to improve the sensitivity which does not require sample modification is cryogenically cooling the RF coil and preamplifier electronics. The reduced level of thermal noise generated by the RF coil, network, and preamplifier lead to a boost in signal-to-noise on the order of 3 while keeping the sample in its original composition and with its natural line width. This progress report shows results obtained with our first 600 MHz 3.2 mm HCN triple resonance CPMAS CryoProbe prototype.
The probe is designed for standard bore magnets and compatible with the well proven CryoPlatform. Cryogenic cooling of the RF coil and preamplifier electronics yields a sensitivity gain of more than 3 compared to conventional probes. This gain is achieved with the sample staying at room temperature.
The probe reaches MAS rates of 20 kHz with 3.2 mm rotors and the MAS3 unit. The CPMAS CryoProbe can be lowered while in the cold state with a new probe lift allowing for easy and safe rotor exchange. Automatic tuning and matching adds to the probe’s comfortable and safe operation.
Thanks to the superior sensitivity of the probe, advanced characterization of an API can be performed without resorting to isotopic labeling. This is illustrated with a CC double quantum correlation on vitamin B12 at natural abundance. The refocused INADEQUATE has notoriously low sensitivity, and it would have taken more than one month acquisition time on a RT probe.
