Chemical analysis by ultrahigh-resolution nuclear magnetic resonance in the Earth’s magnetic field

Abstract

High-resolution NMR spectroscopy is a powerful tool for non-destructive structural investigations of matter1. Typically, expensive and immobile superconducting magnets are required for chemical analysis by high-resolution NMR spectroscopy. Here we present the feasibility of liquid-state proton (1H), lithium (7Li) and fluorine (19F) ultrahigh-resolution NMR spectroscopy2 in the Earth’s magnetic field. We show that in the Earth’s field the transverse relaxation time T2 of the 7Li nucleus is very sensitive to its mobility in solution. The J-coupling constants3 of silicon-containing (29Si) and fluorine-containing molecules are measured with just a single scan. The accuracy of the measured 1H–29Si and 1H–19F J-coupling constants is between a few millihertz up to 20 mHz. This is at least one order of magnitude better than the precision obtained with superconducting magnets. The high precision allows the discrimination of similar chemical structures of small molecules as well as of macromolecules.