UC Davis

A high-volume, high-pressure nuclear magnetic resonance (NMR) probe was developed to be amenable to realistic samples and accommodated by a variety of low-field magnetic assemblies. This high volume, pressure probe was made in response to existing high-pressure probes that could not accommodate samples in excess of a couple milliliters. Initial research with industrial samples of petrol and biomass pretreatment showed that current high-pressure NMR assemblies were not amenable to research with heterogeneous industrial samples, due to their high cost and low volume. The high-pressure NMR probe discussed here was assembled from commercially available parts, modifying a pressure reactor to incorporate a high-pressure NMR probe and circuit assembly. This probe was developed and tested using single-sided, portable magnets. Using relaxometry, rather than resolved chemical shifts, due to the lowered frequency range, macroscopic properties of liquids and mixtures could be observed in real time over the course of pressurization. This work on the high-pressure probe allowed the study of mass-transport mechanisms of salts into a food matrix. Magnetic resonance images (MRI) were taken as apple flesh became pressure-impregnated with salts. These images were used to mathematically model the infusion of molecules into food matrices at high pressure, a feat that had not previously been achieved due to the lack of appropriate high-pressure analytical NMR instrumentation. This information is important in the field of food science where mass transport mechanisms in high-pressure assisted infusion have yet to be fully understood. In addition to the previously mentioned magnetic assemblies, this pressurization probe was interfaced to an opposing pole-facing magnet, an Aspect Instruments imaging magnet, and a SMIS electromagnet. The high-pressure probe was built for high-volume heterogeneous samples. The probe proved robust enough to perform magnetic resonance (MR) relaxometry on other isotopes like sodium, 23Na.