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Uses of State state free precession (SSFP) to enhance signal to noise ratio in high resolution NMR

Grant number: 07/04644-9
Support type:Regular Research Grants
Duration: July 01, 2008 - June 30, 2011
Field of knowledge:Physical Sciences and Mathematics - Chemistry - Analytical Chemistry
Principal Investigator:Luiz Alberto Colnago
Grantee:Luiz Alberto Colnago
Home Institution: Embrapa Instrumentação Agropecuária. Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA). Ministério da Agricultura, Pecuária e Abastecimento (Brasil). São Carlos , SP, Brazil

Abstract

The nuclear magnetic resonance (NMR) signals are normally very weak and have to be average over a large number of scans, to enhance the signal to noise ratio (S/N). Recently, we demonstrate that Steady State free precession sequences (SSFP) can be used to improve the S/N in low resolution NMR, when compared with the conventional techniques such as FID and spin echo. As SSFP does not have dependence on the absolute value of relaxation time (T1), the signals can be averaged with thousands of scans per second. A challenge that comes since the introduction of the pulse and Fourier transform is the use of the SSFP to enhance S/N in high resolution NMR spectroscopy, without phase and amplitude anomalies. The solutions presented so far had not been adopt by the NMR community.The objective of this project will be to evaluate the SSFP sequences already proposed, as well as to study new SSFP sequences with phase shift. We also will be using Filter Diagonalization Method (FDM), that is a new processing technique to transform SSFP signals to frequency domain, without the distortions of caused by the Fourier transform. These fast acquisition techniques will be applied to samples in solution, as well as in heterogeneous products and in vivo biological systems. The experiments will be done with 1H, 13C, 15N, 17O, 31P and others nuclei. We also will evaluated the SSFP sequence as an alternative to cross polarization, in high resolution solid state NMR. (AU)