High-resolution NMR Spectroscopy Of Detection Technology Applied On Inhomogeneous Samples

As a critical method of analysis and detection,Nuclear magnetic resonance(NMR)Spectroscopy can provide important information such as chemical shifts,J couplings,multiplet patterns and related integral area for material composition and molecular structure analysis with high efficiency and without damage.Due to its narrow chemical shift range(0-10 ppm),and splittings of the peak caused by J couplings,peaks will appear crowded or even overlapped in more multiple experiments and the correct spectrum information cannot be obtained.In addition,the broadening of the spectrum peak will also cause the loss of spectrum information.Therefore,how to obtain high-resolution NMR spectra has become one of the topics that the researchers in the field of nuclear magnetic field have been constantly studying.Pure shift can effectively eliminate J coupling splitting effect and retain the chemical shift information of single peak,which enhances the resolution.iMQC technology is immune to changes in magnetic field due to its unique signal properties,therefore,high-resolution spectral information can be recovered under an inhomogeneous magnetic field.In this thesis,we focus on pure shift technology that can eliminate the peak crowding and the iMQC technology that can eliminate the magnetic field inhomogeneity.We carry out corresponding high-resolution NMR spectra studies by designing pulse sequence and discuss the practical applications.The thesis comprises:First,this thesis sorts out the growth and basic principles of NMR briefly,and also introduces several localization methods such as PRESS,STEAM and ISIS.In addition,we analyzed the advantages and disadvantages and their applications.Then we introduced the concept of pure shift and related technology development,and listed several major techniques,such as PSYCHE and ZS.Finally,a detailed summary of iMQC and related applications is analysed simply.Second,combining ISIS with PSYCHE,we propose a method of homonuclear decoupling 1D phase-sensitive localized spectra named ISIS-PSYCHE.We applied this method to 7.0 T small animal MRI imager to explore the localization effect of the experimental method by using chemical and metabolite samples;and the application of method in both localization and decoupling was verified by pig brain tissues and grape.Compared with the PRESS,this method can achieve accurate selection of voxels,eliminate the peak splitting caused by the J couplings effect,and obtain a pure shift spectrum without peak crowding and overlapping.Third,we propose a fast 2D J-resolved spectrum sequence with high-resolution based on the combination of iDQC evolution module,J-modulated detection module and delayed sampling technology.This method can obtain high-resolution information from inhomogeneous field based on iDQC signal.At the same time,the combination of J-modulated detection module and delayed sampling technology can ensure that the method can quickly achieve signal sampling.In this chapter,we deduce the feasibility of the method by theoretical derivation,and use chemical sample and grape for detection,which verifies the ability of the method to recover high-resolution NMR information from the inhomogeneous field quickly.