Stated above, the tightly coupled and defined RF field produced by the millimeter-scale microcoils results in higher signal induction and greater mass-detection sensitivity.  A further benefit of small scale and the use of solenoidal microcoils is that the RF fields are produced in a manner that inherently provides cleaner baselines and fewer unwanted materials artifacts.  Explained above, the solenoid is a tightly-wound, multi-turn magnetic field sensor in which the RF (B1) field is highly focused in the interior region of interest (the region where the NMR flowcell is positioned in the CapNMR probe,) whereas in contrast, saddle coils are typically designed to be less tightly coupled, to provide mechanical clearances to accommodate the passage of an NMR tube into and out of the coil at each sample change.  The “stray” fields (e.g. fields that extend outside the region containing the sample) are significantly greater when employing larger coils that are more loosely coupled to the sample.  These fields penetrate other components (electrical components, mechanical structures, etc.) of the probe, and if protons are present (most materials are protonated), result in baseline artifacts that are virtually impossible to eliminate.  The use of a small solenoidal microcoil means that relative to the size of the coil, the other components of the probe are far more distant than with larger RF coils.  The result is less signal from unwanted sources, flater baselines, and cleaner spectra.   This is particularly important when considering low mass samples, where two probes with the same mass sensitivity can provide drastically different NMR spectral performance.