Effect of ionic strength on perfusive flow in capillary electrochromatography columns packed with wide-pore stationary phases

Towards a microchip-based chromatographic platform. Part 1: Evaluation of sol-gel phases for capillary electrochromatography

“…The most likely explanation for this increase in EOF is due to an increase in pore flow resulting from compression of the double layer as the ionic strength increases. This effect has been previously reported using several different pore sizes [28,29,35], but generally occurs at much lower ionic strengths than we employed here. As such, we believe this increase in flow arises from the nanometer size mesopores, and not the larger macropores.…”

“…Firstly, it has been shown that pore flow supplements the interparticle flow in packed CEC columns and provides a higher EOF and thus more rapid separations. Secondly, the flow profile is more evenly distributed over the cross section of the capillary resulting in a decrease in plate height due to a reduction in the eddy diffusion term in the van Deemter equation [28][29][30][31][32][33][34][35].…”

“…where e 0 is the permittivity of a vacuum, e r is the dielectric constant, R is the universal gas constant, T is the temperature, I is the ionic strength of the electrolyte, and F is the Faraday constant [29,34]. It can clearly be seen that there is an inverse square relation between the double layer thickness and the ionic strength, with an increase in ionic strength resulting in a decrease in thickness.…”

“…For comparison, measurements were also performed using the same BGE in an empty capillary. Figure 2a [29]. The arrows indicate the position of maximum EOF for each column.…”

Perfusive flow and intraparticle distribution of a neutral analyte in capillary electrochromatography

“…Indeed, similar behavior has already been recognized earlier by selective applications in the physical and life sciences, including electrokinetic dewatering of waste sludge or the removal of contaminants from soil [26]. Concerning the permeability of packed capillaries electroosmotic flow (EOF) has shown to offer a far superior dispersion characteristics (compared to pressure-driven flow) which accompanies a reduction of velocity extremes in the mobile phase flow pattern on any time and length scale [27][28][29][30][31]. In particular, plate heights and dispersion coefficients reduced by up to a decade with respect to those normally observed in pressure-driven flow have been reported, especially for weakly and unretained solutes [25,27,29].…”