C-13 DYNAMIC NUCLEAR-POLARIZATION - AN ALTERNATIVE DETECTOR FOR RECYCLED-FLOW NMR EXPERIMENTS

Static NMR experiments on insensitive nuclei (e.g., C-13) have been ge nerally difficult because of low magnetogyric ratios and/or poor natur al abundance, even at the highest magnetic fields available. One metho d of overcoming these sensitivity limitations is dynamic nuclear polar ization (DNP), which can be utilized to enhance NMR signals relative t o those obtained with static NMR detection. In this study, we report a recycled-now DNP apparatus capable of monitoring C-13 scalar-dominate d enhancements 1-2 orders of magnitude greater than those obtainable u sing the conventional recycled-now C-13 NMR experiment. Specifically, a mixture of benzene and several chlorocarbons were continuously ''rec ycled'' through a C-13 DNP spectrometer. Results indicate successful d etection with the C-13 DNP approach in scalar-dominated cases, where a nalytes could not be observed with conventional static or now NMR dete ction in a reasonable length of time.