Nuclear magnetic resonance spectroscopy (NMR) is one of the most powerful methods to analyse and discover molecules. However, the low sensitivity of this technique acts to limit its applicability, while adding substantially to cost. This problem arises from the very low value of the nuclear polarisation from which the NMR signal directly derives. This polarisation depends on the external magnetic field B0 and on the inverse of temperature. While the biggest world NMR apparatuses well beyond 21T, even at this magnetic field, the nuclear polarisation is only 7.10-5 for 1H at room temperature. As consequence of the sensitivity issue, NMR cannot detect molecules at low concentration such as trace product contaminant that can be found in water, petroleum samples, etc. In more recent years, the sensitivity of NMR has been improved by the concept of molecular hyperpolarisation that consists in artificially and transiently increasing the nuclear spin polarisation from the thermal equilibrium. This is performed by polarisation transfer from a more ordered system, such as photons (optical pumping), electrons (e.g. DNP) or purely singlet state nuclear spin order systems (parahydrogen = pH2). With this hyperpolarisation step, the nuclear polarisation levels can be enhanced by a factor of 104-105 above thermal equilibrium levels, resulting in the same gain for the NMR signals. DNP (Dynamic Nuclear Polarisation) is however very costly (more than two million euros), very demanding (absolute temperature) and slow in building hyperpolarisation (> 60 minutes). In contrast, the hyperpolarisation via pH2 is a powerful, low-cost, fast and simple technique. Recently, we have discovered at the University of York a new hyperpolarisation technology based on the use of pH2. This approach, called Signal Amplification By Reversible Exchange (SABRE), has proven to be highly successful for the hyperpolarisation of N-heterocycles, operating on nuclei such as 1H, 13C, 31P, 19F and 15N , there are many classes of molecules for which it success to be sensitive. NMR hyperpolarisation via SABRE will be used to achieve enhancing NMR detection sensitivity of sulfur organic compounds notably S-heterocyclic compounds that are typically found in petroleum and refined petroleum products (such as dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), and benzonaphthothiophene (BNT)). The hyperpolarisation of S-heterocycles compounds by SABRE (can be done in seconds) offers potential advantages of providing structural information and quantity percentage about sulfur-containing contaminants in petroleum, thereby informing petroleum purification and refining to minimize sulfur content in refined products such as gasoline. Furthermore, this sensitivity gain in NMR spectroscopy given by SABRE-hyperpolarisation will allow to perform structural analysis of petroleum products using low-cost, low-magnetic-field (ca. 1 Tesla magnet) high-resolution NMR spectrometers which ideally preferred by the industries in the field.
|Effective start/end date
|1/09/20 → 31/07/22
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