Details

How does a microcoil work?

MRM's miniature, radio-frequency microcoils are wound directly onto fused silica capillaries and packaged for direct compatibility with superconducting magnets (both narrow bore and wide bore) and Varian, Bruker, and JEOL spectrometers.  The frequency of operation and the targeted nuclei for detection must be specified by the customer, but typically involves one of four possible nuclei (1H, 15N, 13C, 19F)* and one of five field strengths (7.0 T, 9.4 T, 11.75 T, 14.1 T, 17.6 T)*. The top of the probe contains the detection coil and associated RF components for frequency-tuned operation, and the base of the probe contains fluid and signal ports and manual tuning wands for frequency adjustment. 

For sample loading, we recommend a Waters CapLCä, including a solvent management module designed by MRM to enable degassing and blanketing functions for preserving the integrity of deuterated solvents.  This combination represents the most sophisticated and robust implementation currently available for performing capillary LC-NMR.  For simpler sample loading needs, the MRM probe can be discretely loaded using a syringe pump and 8-port valve, controlled by the syringe pump.  We invite your phone call to further explore the sample loading options available to you.

Sample loading can be manual or automated.

The primary advantages of employing microcoils for mass-limited applications is high throughput and enhanced performance.

• Sensitivity.  The reduction in RF coil size from ~ 5 mm (typically used in commercial probes) to ~ 1 mm (microcoils) results in a direct sensitivity enhancement of five-fold.  In a NMR technology market where the most verbalized need is sensitivity gain, this single attribute of microcoils represents MRM’s most significant competitive advantage.

• Efficiency.  The detrimental effects due to sample diffusion, convection currents, and the use of large quantities of highly protonated solvents are virtually eliminated at capillary size scales.  The use of more costly deuterated solvents, economically feasible in capillaries, facilitates more efficient data collection.

• Time.  The time required for NMR data collection scales with the square of sensitivity.  Therefore, a gain of five-fold in sensitivity results in a gain of 25-fold in time.  Microcoils provide other time advantages as well.  The time required for sample loading, unloading, and rinsing is reduced by nearly ten-fold due to the high pressures that can be realized at capillary size scales, resulting in a duty cycle (time required for data collection vs. total time required for sample loading, data collection, sample unloading, and capillary rinsing) that is increased from less than 50% for conventional flowprobes to greater than 80% with microcoils.

* MRM's present offering is for 1H detection with 2H lock at field strengths ranging from 7-14 T. Planned for release in summer, 2002 is a 13C indirect detection probe with 1-dimensional magnetic field gradient.