Line width considerations in ³³S nuclear magnetic resonance of aqueous samples

A series of sulfur compounds have been examined by ³³S NMR at 15.3 MHz. The sharpest resonances were found for the inorganic sulfates, with line widths varying from 3.6 Hz for ammonium sulfate to 9.0 Hz for sodium sulfate. Increasing the viscosity of the solvent did not affect the line widths appreciably. Other anions and molecules examined, and their corresponding line widths, included cysteic acid (30 Hz), sodium thiosulfate (60 Hz), ammonium sulfamate (300 Hz), carbon disulfide (400 Hz), concentrated sulfuric acid (1200 Hz) and dimethyl sulfate (2000 Hz). A comparison of the measured line widths and the spin‐lattice relaxation times, T₁, for five of these samples indicated that exchange processes may contribute to and often dominate the ³³S resonance line widths in aqueous samples. No signals were observed in concentrated aqueous solutions of cysteine, adenosine monosulfate or chondroitin sulfate after overnight scans.