Ultracompact NMR: 1H Spectroscopy in a Subkilogram Magnet

Abstract

We demonstrate the first subkilogram permanent magnet and microcoil probe combination capable of 1H nuclear magnetic resonance spectroscopy with subparts-per-million resolution. The 1 T magnet with a weight of 685 g utilizes steel pole faces and flux return paths to provide a sufficiently homogeneous magnetic field in a robust, easy-to-use device nearly immune to environmental influences. The microcoil probe provides a signal-to-noise ratio of 61 in a single data acquisition from 21 nanoliters of water. The line width achieved, 0.24 ppm, can be explained by the measured field variations across the sample volume. The device does not have shim coils, temperature insulation and control, or adequate radio frequency shielding, so simple improvements in these areas will lead to further increases in performance. When combined with commercially available miniaturized electronics, the magnet and the probe described here will form the first handheld device capable of 1H spectroscopy.