Application of NMR-MOUSE and low-field NMR to soft matter characterization

The NMR-MOUSE ( MObile Universal Surface Explorer ) is a small and portable LF-NMR system with one-sided magnet layout that is used to replace the conventional magnet and equipped probe on a LF-NMR instrument. The high magnetic field gradients associated with the one-sided MOUSE magnet result in NMR signal decays being dominated by molecular diffusion effects. The aim of our investigation is to obtain information about the T2 of the water in soft matter, such as hydrogels, meat and to establish if some information can be achieved concerning in vivo skin. In the literature T2 measurements performed on hydrogels[1] and meat[2],[3] carried out by using LF-NMR are already reported. Thus we wanted to repeat the same determination in order to test the available instrument (Bruker Minispec MQ180) and compare the obtained data with those recorded by means of the Bruker NMR-MOUSE. In the literature, at our knowledge, only one investigation on oil-water emulsion has been reported with both a NMR-MOUSE and a conventional low-field NMR (LF-NMR) instrument. [4] The authors observed that : (a) the signal/noise (S/N) ratio is approximately 10 times lower for the NMR-MOUSE than for the bench-top LF-NMR; (b) the trend in relaxation behaviour with increasing oil content measured using the NMR-MOUSE is the reverse of that obtained using bench-top LF-NMR. The large reduction in the S/N ratio is primarily due to the signal only being acquired from a thin slice through the sample, whereas it originates from a larger sample volume when bench-top LF-NMR is used. The reversing of the trend in the decay rates with decreasing oil contents is also expected as a result of the strong magnetic field gradient which greatly decreases the apparent relaxation time of the water due to its rapid diffusion rate.