Benchtop permanent-magnet NMR at 3 T for biomedical and hyphenated applications

Permanent magnets have been a part of NMR spectroscopy since its inception. Massive floor-standing permanent magnets at 1.4 T and 2.2 T first became common in the 1970’s, especially in chemical education. A revolution in the field began in the late 2000s, with the introduction of self-contained benchtop permanent-magnet spectrometers that exploit modern developments in rare-earth hard ferromagnets, low-noise analog RF electronics, FPGA-based digital signal processing, and real-time software control. While not as powerful as their high-field counterparts, the small size, low mass, and low cost of these instruments has opened up many new application areas for NMR. In this talk, I will describe a new design that raises the upper field limit for benchtop NMR to 2.94 T, corresponding a 125 MHz proton Larmor frequency. Our new spectrometer is a compact instrument with a total mass of 28 kg, and it is adapted to automated applications where the sample fluid is delivered by flow, rather than in an NMR tube. Applications include biomaterials, pharmaceuticals, forensics and hyphenation with separation techniques. The design of these instruments is highly physics-enabled, with contributions from every major subject area in a typical university physics curriculum.