Visualization of solute migration in chromatographic columns - Influence of the frit porosity

The dual-perspective, on-column detection method previously described was u sed to observe the effects of the inlet frit on the profiles of chromatogra phic bands. Visualization of bands of iodine was achieved by injecting its dilute solutions in carbon tetrachloride into a glass column packed with a C-18-bonded silica and eluted with carbon tetrachloride, which has the same refractive index as the packing material. The bands were photographed on-c olumn with two standard 35-mm SLR cameras oriented at right angle. The phot ographs were scanned and the digitized images of the sample bands analyzed with proper software. A number of columns, as similar as possible, were fit ted with different 2- and 10-mum porosity stainless steel frits. Subsequent analysis of the digitized band images revealed irregularities in the band shape resulting from frit contributions to band dispersion. The 2-mum frits produced more dramatic effects overall than the coarser frits. Local axial dispersion coefficient values, expressed as local reduced plate height, we re calculated. The results demonstrate the possibly damaging effects of the frit on the band shape. (C) 2001 Elsevier Science B.V. All rights reserved .