Paweł W. Płocharz

Reversed-phase pressurized planar electrochromatography and planar chromatography of acetylsalicylic acid, caffeine, and acetaminophen

We have investigated the use of pressurized planar electrochromatography (PPEC) and planar chromatography (TLC) for reversed-phase separation of a mixture of acetylsalicylic acid, caffeine, and acetaminophen. The mixture was separated on C18 plates; the mobile phase was prepared from acetonitrile (ACN), buffer, and bidistilled water. The effects of operating conditions such as mobile phase composition, type of the stationary phase, and mobile phase buffer pH on migration distance, separation selectivity, and separation time in TLC and PPEC were compared. The results showed that pressurized planar electrochromatography of these drugs is characterized by faster separation, better performance, and different separation selectivity. In conclusion, PPEC is a very promising mode for future application in pharmaceutical analysis.

Pressurized planar electrochromatography, high-performance thin-layer chromatography and high-performance liquid chromatography—Comparison of performance

Kinetic performance, measured by plate height, of High-Performance Thin-Layer Chromatography (HPTLC), High-Performance Liquid Chromatography (HPLC) and Pressurized Planar Electrochromatography (PPEC) was compared for the systems with adsorbent of the HPTLC RP18W plate from Merck as the stationary phase and the mobile phase composed of acetonitrile and buffer solution. The HPLC column was packed with the adsorbent, which was scrapped from the chromatographic plate mentioned. An additional HPLC column was also packed with adsorbent of 5 microm particle diameter, C18 type silica based (LiChrosorb RP-18 from Merck). The dependence of plate height of both HPLC and PPEC separating systems on flow velocity of the mobile phase and on migration distance of the mobile phase in TLC system was presented applying test solute (prednisolone succinate). The highest performance, amongst systems investigated, was obtained for the PPEC system. The separation efficiency of the systems investigated in the paper was additionally confirmed by the separation of test component mixture composed of six hormones.

Progress in planar electrochromatography

Developments in planar electrochromatography in open (PEC) and closed (PPEC) systems are reviewed. The discussion focuses on progress in chamber construction for planar electrochromatography, separating system performance, equilibration of the PPEC process, separation time and selectivity, and the general advantages, disadvantages and prospects of this separation mode.

Pressurized Planar Electrochromatography as the Mode for Determination of Solvent Composition-Retention Relationships in Reversed-Phase Systems

Pressurized planar electrochromatography (PPEC) was introduced by Nurok et al. [1]. The mobile phase in PPEC is driven by the electroosmotic effect through the adsorbent layer of the chromatographic plate. A special plastic film or plate is pressed on to the adsorbent layer to eliminate the vapor phase and flow of mobile phase to the surface of the adsorbent layer. The paper mentioned above, and others [2–6], indicate that this method is characterized by high-efficiency separation, making it very attractive for application in laboratory practice. Contemporary applications have, however, been mainly restricted to separation of test solutes to show the advantages, practical possibilities, and efficiency of PPEC in comparison with conventional planar chromatography (TLC). At the current stage of PPEC development its performance is similar to that of HPLC [1–6]. Separation times in PPEC are reported to be much shorter than in TLC [1, 2, 4], in some circumstances by as much as a factor of 24 [1]. Pressurized planar electrochromatography experiments can be performed under equilibrated conditions [3, 4]. This is another very important advantage of PPEC compared with TLC. The adsorbent layer of the chromatographic plate is prewetted with the mobile phase for the time necessary for equilibration. After prewetting, the mobile phase is used to feed the adsorbent layer during separation process in pressurized planar electrochromatography. Otherwise, conventional planar chromatographic separation usually proceeds under non-equilibrated conditions with the exception of use of a pure solvent as mobile phase. TLC separations are, however, usually performed with mixed mobile phases. Then demixing of the mobile phase occurs during chromatogram development [7]. Even conditioning with mobile phase vapor followed by chromatogram development does not lead to full equilibration of the chromatographic phases.

Planar Electrochromatography in a Closed System under Pressure—Pressurized Planar Electrochromatography

Abstract Pressurized planar electrochromatography (PPEC) is described taking into account last achievements in this mode such as construction of the device and variables influencing on separation efficiency (mobile phase composition, pH of the mobile phase, buffer concentration, applied voltage, chromatographic plate preparation, chromatographic plate type and temperature).

Pressurized planar electrochromatography.

Theoretical backgrounds, development, examples of separations, constructional details and principle of action of devices of pressurized planar electrochromatography (PPEC) are presented. Development of the mode is described in respect of operating variables (composition of the mobile phase, pressure exerted on adsorbent layer, mobile phase flow velocity, temperature of separating system, etc.) influencing separation efficiency (kinetic performance, repeatability, separation time). Advantages of PPEC such as high kinetic performance, short separation time and different separation selectivities, especially relative to conventional thin-layer chromatography, are described. Examples of two-dimensional separations are demonstrated to show high separation potential of the mode when combined with conventional thin-layer chromatography (TLC). The PPEC mode is in infancy stage of development, so its challenges are presented as well.

Equipment and preliminary results for orthogonal pressurized planar electrochromatography

We report combination of overpressured layer chromatography (OPLC) and pressurized planar electrochromatography (PPEC) techniques into a single technique in which both OPLC and PPEC processes proceed simultaneously and orthogonally. The separation process with this new technique is performed in adsorbent layer of a chromatographic plate, which is equipped with special sealing margin on its whole periphery and closed under pressure in special chamber. We have named this separation technique as orthogonal pressurized planar electrochromatography (OPPEC). Examples of analytical and micropreparative (continuous) OPPEC separations are demonstrated.

OPTIMIZATION OF SOME VARIABLES OF ON-LINE INJECTION IN PRESSURIZED PLANAR ELECTROCHROMATOGRAPHY

Pressurized planar electrochromatography (PPEC) is a separating technique, in which an electric field is applied to force movement of the mobile phase through a porous media (electroosmotic effect). High separation efficiency, fast separation, and changes in separation selectivity in comparison to liquid chromatography, especially to thin-layer chromatography (planar chromatography, TLC) are features of this technique. Our group has recently introduced the prototype device, which enables simultaneous on-line injection of six samples on chromatographic plate in a stream of the mobile phase. In this paper influence of some operating variables of on-line injection mode on efficiency of PPEC separation system is shown and discussed.

Electrochromatography Methods: Planar Electrochromatography

Planar electrochromatography is a technique in which mixture components are separated in adsorbent layer of a chromatographic plate placed in electric field. In such separation system a mobile phase movement stems from electroosmosis phenomenon. Partition and electrophoresis mechanisms are involved in separation of mixture components with this technique. Two principal modes of planar electrochromatography are described: planar electrochromatography in an open system (PEC) and planar electrochromatography in a closed system (pressurized planar electrochromatography, PPEC). The development of both modes is presented beginning with the first paper on electrochromatography by Pretorius et al. in 1974 and finishing with the last papers by Dzido et al. in 2010. Constructional development of equipment to planar electrochromatography is provided and influence of operating variables on separation efficiency as well. The advantages and challenges of PPEC technique are especially discussed.

High-performance thin-layer chromatography and pressurized planar electrochromatography of some diastereomeric amino acid derivatives in reversed-phase system with carboxylic acid mobile phase buffers

The separation of 1-fluoro-2,4-dinitrophenyl-5-L-valine amide (FVDA) diastereomeric derivatives of aspartic acid, cysteine, and histidine by means of high-performance thin-layer chromatography (HPTLC) as well as pressurized planar electrochromatography (PPEC) techniques in systems with HPTLC RP-18W plates and the various acetonitrile-buffer mobile phases is presented. The influence of the mobile phase components, i.e., acetonitrile concentration and buffer kind on migration distance of the solute zones, was investigated. The effect of mono (formic) and various dicarboxylic acids (oxalic, malonic, maleic, malic, succinic, tartaric, and pimelic) as the mobile phase buffer components on the solute retention was studied. It is observed that an increase of acetonitrile content of the mobile phase affects the solute zone migration and retention in PPEC and HPTLC. What is more, the separation selectivity in the latter and former techniques differs. The PPEC mode presents a higher efficiency in comparison with HPTLC. The solute separation with electromigrational system is more fragile on the kind of acid used as mobile phase buffer component than with chromatographic method. Nevertheless, the influence of the kind of mobile phase buffer component on solute selectivity and retention in both techniques was determined. The electrokinetic (zeta) potential of the stationary-mobile phase interface was measured and compared with the solute retention data of both techniques.