The shape of the NMR spectrum and the spin-lattice relaxation in aqueous suspensions of charcoals

H-1 NMR spectra of aqueous suspensions of charcoals used in the oximetry of living tissues and spin-lattice relaxation times T-1 of individual lines of the spectra were measured. The spectra involve two lines. The higher intensity line was assigned to protons of water molecules located in the space between charcoal particles and in the macropores of these particles, whose volume was estimated at about half the volume of the charcoal particles. The dependence of T-1 for this line on the particle size L was used for estimating the diameter of the macropores and the relaxation time T-1,T-s of protons of water molecules in the surface layer. The second line, having a relative integral intensity of approximate to0.04, was shifted towards the high-field region by approximate to5 ppm. The time T-1 (approximate to 50 mus) for this line did not depend on L. This line was assigned to protons of water molecules located in charcoal micropores. The disintegration in the structure of hydrogen bonds resulted in a shift of the NMR signal and a dramatic lowering of the freezing point of water in the micropores. The second line occurred in spectra of suspensions cooled to -80 degreesC, whereas the first line disappeared in the range from 0 to -10 degreesC.