4.5 K Cooling System for a Cryogenically Cooled Probe for a 920 MHz NMR

Effect of dielectric properties of solvents on the quality factor for a beyond 900 MHz cryogenic probe model

“…Thus, from the viewpoint of sample noise, non-polar organic solvents are expected to be the best choice for a very high-field NMR spectrometer. Furthermore, it is probable that if the RF coil temperature is decreased from 15 to 4 K, the sensitivity gain may be double of that at 15 K, assuming the sample loss for a non-polar organic solvent is negligible [23]. The use of non-polar organic solvents is common in the field of chemical analysis of natural compounds or metabolomics studies [39], though low sensitivity is an essential problem in both cases.…”

“…Furthermore, the effect of the real part of the relative dielectric permittivity, e 0 , has never been explored, although it affects the transverse electric field strength on the sample and thus changes the sample loss. Both effects are demonstrated here on the quality factor of a 930 MHz cryogenic probe model [22,23] in connection with aqueous salt solutions, buffered aqueous solutions, and polar and non-polar organic solvents.…”

Hyphenated NMR Methods in Natural Products Research, Part 1: Direct Hyphenation

“…NMR is a comparatively insensitive spectroscopic technique, a fact that originates from the small difference between energy levels of atomic nuclei, which leaves only a small population excess of spins occupying the ground state at thermal equilibrium and giving rise to the NMR signal. However, already early ironmagnet spectrometers exhibited sensitivity comparable to that of refractive index (RI) detectors [4], and the sensitivity of commercial NMR instruments improves continuously [11], [12], [13]. Under ideal conditions, the signal-to-noise ratio in NMR is proportional to the 7/4 power of the magnetic field strength.…”

“…This applies especially to water, which gives a relatively broad and difficult to suppress signal. CH 3 CN, solvent suppression will be further improved by applying 13 C decoupling that collapses 13 C-satellites in the 1 H-NMR spectra.…”

“…Because deuterated solvents usually contain 99.8 atom % of deuterium, suppression of the residual solvent signal will still be necessary. Since 1.1 % of the 1 H resonance of CH 3 CN consists of13…”