Automatic removing method of the frequency shift for dosy analysis based on the nonlinear fitting

This paper improves a preprocessing method of diffusion ordered NMR spectroscopy (DOSY). DOSY is molecular analysis method, and it estimates a spectrum and a diffusion coefficient of molecule. In general, the observed signal is distorted as the shifting of frequency by the heat of pulse excitation and the magnetic inhomogeneity. Therefore, the observed signal is corrected before the DOSY analysis, and its correction is based on a shift amount of spectrum which is estimated by the human hand. This paper proposes an automatic removing method for the frequency shift of observed signal of DOSY. The proposed method estimates the shift amount basing on the center frequency of a Lorentz peak, and the center frequency is estimated by the nonlinear fitting. A simulation and an actual data analysis show that the proposed method automatically gives the similar result by the correction of the human hand.