Comparison of Overpressured-Layer Chromatography and High-Performance/High-Pressure Layer Electrochromatography Using the New Prototype Equipment in Various Operational Modes

Abstract

In our previous paper we have presented the new prototype equipment and introduced a new analytical technique—high-performance/high-pressure layer electrochromatography (HPLEC), a combination of overpressured-layer chromatography (OPLC) and pressurized planar electrochromatography (PPEC). In this paper, the work of the equipment in various operational modes is investigated. Some difficulties and challenges related to various aspects of separation are discussed. The OPLC and HPLEC techniques are compared in terms of selectivity and performance. The results show that our equipment can be successfully used for singe- and multichannel OPLC and HPLEC separations in various sample application and detection modes. It includes the high-throughput, multichannel, and fully automated online separation of multiple samples simultaneously. The equipment allows for the independent optimization of various operational parameters. HPLEC combines the advantages of column/capillary and planar separation techniques while overcoming their limitations. It also combines the advantages and overcomes the drawbacks of OPLC and PPEC. It provides hydrodynamic flow of the mobile phase, irrespective of the voltage used and/or the mobile phase composition. Thus, any optimization of the composition and the voltage can be used independently. Both can be used to obtain the required selectivity of separation. The voltage can be used to facilitate the mobile phase flow and accelerate the analysis.

Reverse-Polarization High-Performance Layer Electrochromatography—A New Approach to Anion Separation

“…In our previous experiments, acidic mobile phases were used for the separation of a standard set of solutes (mainly azo dyes) in various modes of normal-polarization HPLEC [2]. The solutes being separated were mainly in the cationic form.…”

“…In our previous papers, we have presented new prototype equipment for highperformance (high-pressure) layer electrochromatography (HPLEC) [1] and some preliminary results of examples of separations in various working modes [2]. The new separation technique is a combination of overpressured-layer chromatography (OPLC) [3][4][5][6][7] and pressurized planar electrochromatography (PPEC) [8][9][10][11].…”

“…Some other capabilities of our technique, such as simultaneous separation of multiple samples as well as the use of various sample application and detection methods, are characteristic advantages. All this makes our prototype equipment able to work in many combinations of sample application and detection modes (fully online, fully offline, online + offline, or offline + online) and with various separation techniques (OPLC, PPEC, HPLEC, single-or multichannel separation) [1,2].…”

“…In our previous paper [2], we have shown some examples of comparisons of OPLC and HPLEC separations. The experiments were carried out in various working modes and in various separation conditions.…”

“…• investigation of reverse-polarization HPLEC separation mode with our prototype equipment, using a set of solutes similar to those used before in normal-polarization HPLEC [2]; • comparison of the results with OPLC in similar separation conditions; • investigation of the influence of the change in the electric field direction, especially the influence of the redirection of the electroosmotic effect against the hydrodynamic flow of the mobile phase on the total flow profile and direction, backpressure and velocity limit of the mobile phase flow, velocity and direction of solute migration, and overall performance of separation; • evaluation of any possible side effects of the approach; • discussion of the advantages and disadvantages of the reversed-polarization HPLEC mode and its practical potential.…”