Nuclear magnetic resonance studies of solvent flow through chromatographiccolumns: effect of packing density on flow patterns

NMR (nuclear magnetic resonance) techniques have been used to measure and c haracterise solvent flow through chromatographic columns. NMR imaging was u sed to track an injection of D2O. PGSE (pulsed gradient spin echo) NMR was used to measure the flow-rate dependence of axial and transverse apparent d iffusion. A combination of these two techniques (dynamic NMR imaging) gave the spatial distribution of the local velocity and apparent diffusion throu gh a cross-section of the column. Significant column wall effects were obse rved and these effects were found to be highly dependent upon the column pa cking density. The column performance was assessed in terms of the HETP (he ight equivalent to a theoretical plate) determined by the NMR techniques em ployed. (C) 2001 Elsevier Science B.V. All rights reserved.