Cryogenically cooled flow probes

Recent LC-NMR Probe Developments 7.4.2.1 Cryogenically Cooled Flow Probes... 

Probes usually have variable temperature control to run experiments at temperatures selected by the analyst. Cryogenically cooled probes can improve the resolution of a system, so that a 600 MHz spectrometer equipped with such a probe can provide resolution equivalent to a 700-800 MHz instrument. New probe designs with flow-through sample holders are commercially available, for use in coupled HPLC-NMR instruments and HPLC-NMR-MS instruments. These hyphenated instruments are discussed under applications later in the chapter. 

Another probe choice is that of the flow variety. These probes come in several formats however, they all have one thing in common. This conunon feature is that of a flow cell. There are many different varieties of flow cells customized to the types of analysis that need to be done. These differences vary from either the thickness of the flow cell (SFC-NMR) to the actual volume the cell holds (e.g., flow NMR, LC-NMR, LC-SPE-NMR, etc.). An additional element that has truly enhanced the world of LC-NMR is the introduction of the flow cell inserts for cryogenically cooled probes. This has really taken this application of NMR to a much more productive level. The NMR community refer to flow cell sizes based... 

There are also more specialized varieties of flow probes that allow a researcher to analyze data acquired for samples in the submicrogram level. These probes include the many variants of the protasis/MRM microcoil and the inserts that one can utihze in the cryogenically cooled probes mentioned above. Both of these probes offer exceptional capabilities to acquire data on samples of very limited mass as well as very good spectral quality and reproducibility. In addition, the utilization of the smaller cell volumes also requires less effort in the experimental set-up around the suppression of residual solvent inherent in the samples of this size. 

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