A solid-liquid microextraction approach from a spot in an adsorbent layer of a chromatographic plate.

A new approach to extracting substances from a spot on a chromatographic plate for subsequent liquid chromatography-mass spectrometry analysis is described. This method involves extraction in a solid phase (an adsorbent layer of a chromatographic plate) - a liquid system using a simple device. For a single extraction of six selected coccidiostats from the adsorbent layer on the chromatographic plate with silica gel, 50 µL of methanol was used for 5 min.

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

High-performance layer electrochromatography (HPLEC) combines the advantages of overpressured-layer chromatography (OPLC) and pressurized planar electrochromatography (PPEC) while overcoming some of their limitations. HPLEC equipment can work in various HPLEC, OPLC, and PPEC modes. The equipment enables HPLEC analysis also with an electroosmotic effect directed against the hydrodynamic flow of the mobile phase.

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

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.

High Performance (High Pressure) Layer Electrochromatography Separation Technique: Equipment and Preliminary Results.

We present a new prototype device and propose a new analytical technique: high performance (high pressure) layer electrochromatography (HPLEC). The equipment provides a combination of overpressured layer chromatography (OPLC) and pressurized planar electrochromatography (PPEC), yet it still enables researchers to perform each of these analyses separately. In comparison to PPEC, HPLEC provides hydrodynamic flow of the mobile phase, irrespective of the voltage used and the mobile phase composition.

Solvent Front Position Extraction and some conventional sample preparation techniques for the determination of coccidiostats in poultry feed by LC-MS/MS.

Solvent Front Position Extraction is a novel technique developed for effective sample preparation of biological samples containing coccidiostats prior to LC-MS/MS. In this study the technique was used for isolation and determination of seven coccidiostats, from both main groups being: ionophores and chemical coccidiostats. Its effectiveness was evaluated by comparing with other sample preparation procedures, used in European routine laboratories.

Preparation of Antihypertensive Drugs in Biological Matrix with Solvent Front Position Extraction for LC-MS/MS Analysis.

Solvent front position extraction procedure was used to prepare biological samples containing selected antihypertensive drugs (ramipril, lercanidipine, indapamide, valsartan, hydrochlorothiazide, perindopril, and nebivolol). Substances separated from the biological matrix components (bovine serum albumin) were quantified by means of liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Sample preparation process was performed with the use of a prototype horizontal chamber with a moving pipette driven by a 3D printer mechanism enabling a controlled eluent flow velocity.

Reversed-phase pH gradient thin-layer chromatography of biologically active substances with controlled developing solvent velocity.

For the first time, stepwise pH gradient thin-layer chromatograms of biologically active substances with controlled developing solvent velocity are presented and described in the paper. Change in buffer pH of the mobile phase solution influences retardation, selectivity, and shape of the separated substances' spots. The conducted research has confirmed that the mobile phase's pH gradient could be an essential factor to optimize the conditions of the separation of substances in reversed-phase high-performance thin-layer chromatography.

Optimization of Adsorbent Layer Type and Developing Solvent in Coccidiostats Sample Preparation with Procedure of Solvent Front Position Extraction.

Coccidiostats are drugs used against coccidiosis, a common disease among breeding animals. Their widespread application leads to the appearance of their residues in food, which is potentially harmful for human health and life. The European Union has established limits of concentrations of these drugs in premixtures and food.

Comparison of the Retention and Separation Selectivity of Aromatic Hydrocarbons with Polar Groups in RP-HPLC Systems with Different Stationary Phases and Eluents.

In this manuscript, the retention of aromatic hydrocarbons with polar groups has been compared for systems with various nonpolar columns of the types from C3 to C18 and different mobile phases composed of methanol, acetonitrile, or tetrahydrofuran as modifiers. The selectivity separation of the solutes in systems with different adsorbents, when one eluent modifier is swapped by another, has been explained, taking into account molecular interactions of the solutes with components of the stationary phase region (i.e.

Solvent front position extraction with semi-automatic device as a powerful sample preparation procedure to quantitatitation of tryptophan in human plasma.

In the paper the results of the tryptophan determination in human plasma samples prepared with the novel Solvent Front Position Extraction (SFPE) technique are presented. The SFPE procedure is used for preparation of real biological sample for the first time. The results obtained using SFPE are compared with those using the classical sample preparation procedure.

Retardation of some drugs in thin-layer chromatographic systems with impregnated silica gel plates with hen's egg white and bovine serum albumin.

The influence of impregnation the chromatographic plate adsorbent layer, silica, with hen's egg white albumin (OVA) or bovine serum albumin (BSA) on the retention of some popular medicines (paracetamol, aminophenazone, theophylline, caffeine, acetanilide, ciprofloxacin, tramadol, acetylsalicylic acid, acebutolol) is investigated. The effect of composition and buffer pH of the mobile phase on solute separation selectivity is also studied. The chromatographic systems with and without above mentioned albumins and their influence on investigated drug retention are compared.

Optimization of the procedure of solvent front position extraction for preparation of multi-component sample for instrumental analysis.

Solvent Front Position Extraction (SFPE) procedure has been recently introduced as a novel concept for multi-component sample preparation. According to the procedure, thin-layer chromatography (TLC) is used to separate the compounds of interest from matrix components, and to focus them into a common zone from which the compounds are extracted and transferred to apparatus for instrumental analysis. In the paper, we investigate different adsorbent types of the chromatographic plates and various mobile phases, including pH of their buffers, in respect of optimization conditions of the SFPE procedure.

Reversed-phase stepwise gradient thin-layer chromatography of test dye mixtures with controlled developing solvent velocity.

The new approach to the development of planar chromatogram with controlled developing solvent velocity was implemented for gradient reversed-phase chromatography of a test mixture of dyes. The developing solvent components were directly delivered onto the surface of the C18 type of silica adsorbent layer with controlled velocity by moving pipette combined with two syringe pumps. The eluent components were mixed onto the adsorbent layer, so in this way, there was no dwell volume of the developing solvent during gradient chromatogram development.

Solvent Front Position Extraction with Semi-Automatic Device as a Powerful Sample Preparation Procedure Prior to Quantitative Instrumental Analysis.

The new prototype device is applied to the Solvent Front Position Extraction (SFPE) sample preparation procedure. The mobile phase is deposited onto the chromatographic plate adsorbent layer by the pipette, which is moved, according to programmed movement path, by a 3D printer mechanism. The application of the prototype device to SFPE procedure leads to the increased repeatability of the results and significant reduction of the analysis time in comparison to the classical procedure of chromatogram development.

Some theoretical considerations on preparative separation with orthogonal pressurised planar electrochromatography.

In this work, separation of multicomponent mixtures containing components with the same and different electrophoretic mobility by using orthogonal pressurised planar electrochromatography is studied theoretically. Additionally, a simple way for determination of a maximum amount of mixture causing volume overload of flat/planar columns used in this technique is presented. In the next stage, effects of change in different parameters on process performance by simulation case studies are investigated.

Thin-layer chromatogram development with a moving pipette delivering the mobile phase onto the surface of the adsorbent layer.

The new approach to the development of thin-layer chromatograms is presented. For the first time we show flexible mobile phase dosage onto the surface of the adsorbent layer by moving pipette combined with precise syringe pumps. The pipette is driven into movement by computer controlled 3D machine (modified 3D printer mechanism).

The influence of addition of ion-pairing acid and organic modifier of the mobile phase on retention and migration of peptides in pressurized planar electrochromatography system with octadecyl silica-based adsorbent.

In our previous papers we have investigated the influence of the mobile phase composition on mechanism of retention, selectivity and efficiency of peptide separation in various high-performance thin-layer chromatography (HPTLC) systems with commercially available silica-based adsorbents. We have also investigated the influence of pH of the mobile phase buffer on migration and separation of peptides in pressurized planar electrochromatography (PPEC). Here we investigate the influence of concentration of ion-pairing additive, and concentration and type of organic modifier of the mobile phase on migration of peptides in PPEC system with octadecyl silica-based adsorbent, and with the same set of the solutes as before.

The influence of pH on retention and migration of peptides in systems with octadecyl silica-based adsorbent by high-performance thin-layer chromatography and pressurized planar electrochromatography techniques.

In our paper we investigate the influence of pH of the mobile phase buffer, on retention of peptides in both: normal phase (NP) and reversed phase (RP) high-performance thin-layer chromatography systems (HPTLC), using C18 silica-based adsorbent. We also compare the influence of pH on retention and/or migration distance of peptides in separation systems of HPTLC and PPEC (pressurized planar electrochromatography) techniques. Our results show, that the change of pH of the mobile phase buffer can be used for two-dimensional HPTLC separation of peptides, but much stronger change of separation selectivity can be obtained by overall inversion of separation system type (NP/RP), as we have described before (Gwarda et al.

Preliminary results for interval feeding the orthogonal pressurized planar electrochromatography system with sample solution for its preparative separation.

The orthogonal pressurized planar electrochromatography (OPPEC) is an example of 2-D separation technique, in which two simultaneous and orthogonal processes of electrophoresis and chromatography are involved in the separation mechanism. In the case of preparative separation of substances characterized by different electrophoretic mobility, such separation system can be constantly fed with the sample solution and the separated components can be constantly collected at its outlet. In the paper, as opposed to the previous studies, we discuss the capabilities of OPPEC technique for preparative separation of substances characterized by the same electrophoretic mobility.

Inversion of type of separation system in planar chromatography of peptides, using C18 silica-based adsorbents.

Our previous results show, that C18 silica-based adsorbents used in high-performance thin-layer chromatography (HPTLC), provide complex retention mechanism basing on various polar and nonpolar interactions. Here we present, that in chromatography of peptides, due to mixed-mode properties of these adsorbents, there is a simple way to obtain inversion of separation system type (from reversed-phase, RP, to normal-phase, NP, and vice versa). The results presented provide detailed information how to obtain inversion mentioned and reflect the extent (the type and concentration of organic solvent, the type and concentration of ion-pairing reagent in the mobile phase) of this phenomenon.

Influence of carboxylic ion-pairing reagents on retention of peptides in thin-layer chromatography systems with C18 silica-based adsorbents.

One of the main problems related to chromatography of peptides concerns adverse interactions of their strong basic groups with free silanol groups of the silica based stationary phase. Influence of type and concentration of ion-pairing regents on peptide retention in reversed-phase high-performance liquid chromatography (RP-HPLC) systems has been discussed before. Here we present influence of these mobile phase additives on retention of some peptide standards in high-performance thin-layer chromatography (HPTLC) systems with C18 silica-based adsorbents.

Influence of some operation variables on continuous separation process of orthogonal pressurized planar electrochromatography.

Orthogonal pressurized planar electrochromatography (OPPEC) is the new separation technique, in which two simultaneous and orthogonal processes of electrochromatography/electrophoresis and chromatography proceed under external pressure. It means in the OPPEC separation system a mobile phase solution hydrodynamically flows against adsorbent layer of the chromatographic plate and electric field is orthogonally applied to it. This technique can be applied to analytical and preparative separations.

Influence of the Modifier Type and its Concentration on Electroosmotic Flow of the Mobile Phase in Pressurized Planar Electrochromatography.

The aim of this work was to find a relationship between electroosmotic flow (EOF) velocity of the mobile phase in pressurized planar electrochromatography (PPEC) and physicochemical properties like zeta potential, dielectric constant, and viscosity of the mobile phase as well as its composition. The study included different types of organic modifiers (acetonitrile, methanol, ethanol, acetone, formamide, -methylformamide and ,-dimethylformamide) in the full concentration range. In all experiments, chromatographic glass plates HPTLC RP-18 W from Merck (Darmstadt) were used as a stationary phase.

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).

A Modified Device for Pressurized Planar Electrochromatography and Preliminary Results with On-Line Sample Application.

Pressurized planar electrochromatography (PPEC) is a separating technique in which an electric field is applied to force the mobile phase movement through a porous media (electroosmotic effect). High separation efficiency, fast separations and changes in separation selectivity in comparison to liquid chromatography, especially thin layer chromatography (planar chromatography, TLC), are features of this technique. Constructional methodological challenges to PPEC are obstacles to its development and application in laboratory practice.