Preliminary Studies Of Pure Shift NMR Based High-Resolution Diffusion And Relaxation Spectroscopy

As an important analytical method,NMR Spectroscopy has found wide applications in chemistry,biology and materials because of its powerful functions in the illustration of molecular structures and the dynamic analysiss of diffusion and relaxation.However,due to limited chemical shift range(?10 ppm)and peak splittings caused by J coupling in 1D proton NMR spectra,spectral congestion or even overlap is generally observed in complex sample detection,making it impossible to reconstruct high-resolution spectra and get accurate the detection on,in particular,diffusion and relaxation information.Therefore,how to solve the problem of spectral congestion and achieve high-resolution extraction of diffusion and relaxation information means the significance for applications to the dynamic analysis.Among studies on overcoming spectra congestion and improving spectral resolution,the improvements on magnetic field strength by hardware and spectroscopic techniques on high-dimensional spectra are two major approaches.In this thesis,we proposed new NMR method based on pulse sequence design and data processing to overcome spectral congestion and improve spectral resolution.According to the characteristics of pure shift signal evolution in simplifying spectral splitting,we introduce the pure shift technique into diffusion and relaxation evolution mechanism to establish a set of NMR method aiming for high-resolution detection and dynamic analysis on complex samples.The thesis specifically includes,First,this thesis reviews the basic principle and development history of NMR spectroscopy,specially on pure chemical shift techniques,Diffusion Ordered Spectroscopy(DOSY)and transverse relaxation approaches.Then their merit and demerit are analysed simply.Second,we introduce the pure chemical shift technique into DOSY and proposed a high resolution DOS Y method for measurements on complex samples.The feasibility of this method was theoretically analyzed by detailed derivation and experimentally demonstrated by various mixture samples.Especially,the comparison between the proposed method and conventional DOSY method were performed.It was proved that the proposed method achieves high-resolution DOSY measurments on complex mixture samples that suffers from crowded NMR resonances,along with chemical exchange effects.Third,we bring the pure chemical shift technique to relaxation measurements and design a high-resolution transverse relaxation detection method.After the theoretical analysis on the feasibility of the proposed method,three experiments acquired from simple chemical sample,complex chemical sample,and medicine solution are performed to demonstrateded the performance of the proposed method on overcoming spectral congestion and high RF power deposition during relaxation measurements on complex samples.