Industrial applications of 33S NMR spectroscopy

33S NMR spectroscopy is potentially an adequate method for both qualitative and quantitative analysis of mixtures of organosulphur compounds. Kosugi62 has reported the 33S spectra of mixtures of 1- and 2-naphthalenesulphonates and of 1,5- and 2,6-naphthalene disulphonates at concentrations of approximately 0.15 M in D20. In both cases, (NH4)2S04 was used as an internal standard to determine chemical shifts and for quantitative analysis. At a magnetic field of 5.9 T, the 33S spectra of the two mixtures show two quite sharp and well-resolved resonances, and the results reported indicate that the quantitative analysis of these isomers is possible with a relative error of less than 10%. 

Quantitative analysis is possible with good accuracy if the 33S spectra are characterized by a good S/N and if the signals of the species to be determined are well resolved. It must be considered that in 33S NMR spectra, baseline distortions can seriously endanger the final results. 

The application of 33S NMR spectroscopy to the qualitative characterization of sulphur compounds in coals and petroleum has been another subject of a certain interest.99-10 The presence of organic and inorganic sulphur derivatives in variable amounts in fuels has serious economic and environmental consequences. Coals and crude oils can be treated chemically to reduce sulphur content, and it is of fundamental importance to develop an analytical method to rapidly and accurately analyse sulphur before and after the desulphurization process. 

170 NMR data confirms this conclusion. The 33S chemical shifts reported vary from —6 to —3 ppm, but these values are not particularly indicative, since they 

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