DETERMINATION OF THE APPARENT TRANSVERSE AND AXIAL-DISPERSION COEFFICIENTS IN A CHROMATOGRAPHIC COLUMN BY PULSED-FIELD GRADIENT NUCLEAR-MAGNETIC-RESONANCE

Pulsed field gradient nuclear magnetic resonance permits the direct de termination of the coefficient of apparent dispersion of a solute in a chromatographic column. Axial and transverse dispersion coefficients can be measured independently as a function of the flaw velocity of th e mobile phase. Experiments have been carried out using water as the m obile phase, porous C18 silica as the stationary phase, and water as t he probe (self-dispersion). The results are reported and compared to s imilar ones obtained previously by various authors, using conventional chromatographic techniques. The NMR method shows potential for the in vestigation of the structure and homogeneity of the packing of large d iameter columns for preparative chromatography. It permits direct acce ss to local values of these coefficients instead of measuring averages as classical methods do.