17G-9 |
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A. GOLOSHEVSKY1, J. H. Walton2, M. V. Shutov2, J. S. De Ropp2, S. D. Collins3, and M. J. McCarthy4. (1) Dept. of Biological Systems Engineering, Univ. of California, Davis, 1 Shields Ave., Davis, CA 95616, (2) NMR Facility, Univ. of California, Davis, 1 Shields Ave., Davis, CA 95616, (3) Laboratory for Surface Science & Technology, Univ. of Maine, 5764 Sawyer Research Ctr., Orono, ME 04469-5764, (4) Dept. of Food Science & Technology, Univ. of California, Davis, 1 Shields Ave., 231 Cruess Hall, Davis, CA 95616 The ability to monitor the viscosity is essential for control of unit operations and for assuring product quality. A non-invasive mode of operation and the possibility of on-/in-line determination of parameters are the advantages of Nuclear Magnetic Resonance (NMR) based measurements. Placing analytical instruments in- or on-process lines would permit control of the material as it is processed, enabling real-time analysis. Our objective is to provide an effective on/in-line sensor by building a small scale magnetic resonance system based on a low field magnet and a miniaturized radiofrequency (RF) coil. Viscosity can be determined from the NMR imaging of sample flow in a tube by analysis of the velocity profile. We conducted NMR experiments using a commercial spectrometer connected to a 0.6 T superconducting magnet. A 3.5 mm diameter Helmholtz spiral RF coil was fabricated by photolithography and electroplating. The 0.6 T magnetic field used in our experiments is much lower than the magnetic fields of recent reports on NMR microscopy. Therefore, it was of importance to verify acceptable system performance. The coil performance was tested for both NMR spectroscopy and imaging applications. NMR spectra of water, methanol and 1-propanol were obtained as well as static and flow images. The spectral resolution allowed chemical identification. Viscosity of water was estimated from the experimental velocity profile and was equal to the expected value of 1 cP. To the best of our knowledge this is the first NMR measurement of viscosity, which was achieved by using a microfabricated RF coil. The success of the spectral and imaging experiments demonstrates that a small scale low field NMR system would be effective as an industrial sensor for process measurements.
Session 17G, Food Engineering: Physical, chemical and electrical properties
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