Analysis of biological fluids using 600 MHz proton NMR spectroscopy: application of homonuclear two-dimensional J-resolved spectroscopy to urine and blood plasma for spectral simplification and assignment.
The application of 600 MHz two-dimensional J-resolved 1H NMR spectroscopy (JRES) to the analysis of human urine and blood plasma is demonstrated. This method when applied at very high field gives a rapid means of simplifying and aiding the assignment of highly overlapped resonances of minor metabolites in biofluids. Using this approach, mixtures of drug and endogenous metabolites were identified in untreated urine samples, the signals of which were extensively overlapped in single pulse 600 MHz spectra. For untreated blood plasma samples the JRES experiment was also effective for the selective attenuation of signals from the plasma proteins thus revealing strong well-resolved signals from the low molecular weight components. For the first time it was shown to be possible to assign in detail the spectra region from 3 to 4 ppm in blood plasma, including the complete assignment of the signals from alpha- and beta-glucose. JRES spectra of plasma were much easier to interpret and had a much higher information content than equivalent one-dimensional Hahn spin-echo spectra, thus aiding the identification of non protein-bound low molecular weight metabolites in plasma.