A study of J-coupling spectroscopy using the Earth’s field nuclear magnetic resonance inside a laboratory

Abstract

In this paper, an instrumentation of the Earth's field nuclear magnetic resonance (EFNMR) inside a laboratory is presented. A lock-in analysis (LIA) technique was proposed to enhance the signal-to-noise ratio (SNR). A SNR of 137.8 was achieved in a single measurement for 9 ml tap water, and the LIA technique significantly enhanced the SNR to 188 after a 10-average in a noisy laboratory environment. The proton-phosphorus coupling in trimethyl phosphate ((CH(3)O)(3)PO) with J-coupling J[H,F]=(10.99±0.013) Hz has been demonstrated. The LIA technique improves the SNR, and a 2.6-fold improvement in SNR over that of the frequency-adjusted averaging is achieved. To reduce the noise in EFNMR, it was suggested that the LIA technique and the first order gradient shim be used to achieve a subhertz linewidth.

Microtesla NMR J-coupling spectroscopy with an unshielded atomic magnetometer

“…The precession signal can be approximated as a decaying beat (see Fig. 6) of two spectral components, with a separation given by the 3 J[H, P ] constant, which amounts to about 10 Hz [19,20,25].…”

Signal Analysis and Liver Tumor Discrimination by Using a High-T_c SQUID-Based Low-Field NMR System in Hospital

“…However, the measuring field which fluctuates with time due to the motion of magnetic objects and other changes of magnetic field in hospital causes the distortion of averaged signal. In the past, the time-domain frequency adjusted average method was used for averaging the NMR signal in a laboratory environment [18], [19]. Here we proposed the fluxgate-guided TFAA method to correct the frequency variation.…”

Magnetic resonance signal moment determination using the Earth’s magnetic field

“…lowest SNR) NMR option, and can serve as a prototyping tool before design of higher field permanent magnet arrangements. EF NMR systems have already been used for applications such as spectroscopy [40,41], diffusion measurement [42][43][44][45], flow metering [46] and imaging [47,48].…”