Part I. Comparison of separations of fatty acids on RP-18 plates with and without a concentrating zone. J. Planar Chromatogr. 15, 332-340 (2002). Fatty acids from pentanoic acid to tricosanoic acid have been separated on RP-18 with and without concentrating zone. Visual inspection of the chromatograms revealed that better separation of the acids was obtained on RP-18 plates with concentrating zones because compact chromatographic bands were obtained. TLC of 19 fatty acids on RP-18 with methanol - water 9:1; 19:1 or methanol. Visualization by exposure to iodine vapor.

J. Planar Chromatogr. 19, 324-326 (2006). GC-MS investigation of dichloromethane extracts from three different types of RP-18 modified silica gel used as TLC adsorbents. Alkenes and carbonyl compounds (two different aldehydes and one ketone) were identified.

J. Planar Chromatogr. 7, 157-159 (1994). TLC of morphine (as dansyl derivative, 5 - 80 ng) and 7-aminoflunitrazepam (as fluorescamin derivative, 100 pg - 2.5 ng); fluorescence enhancement was performed by dipping the developed plate (no details) in a solution of Triton X-100 in a 1:7 mixture of chloroform and hexane. Pre-chromatographic reactions on the TLC plate using a commercially available sampler.

J. Chromatogr. Sci. 46 (6), 565-573 (2008). Investigation of selected amino acid standards on cellulose layers using organic-aqueous eluent systems modified with neutral and chaotropic salts: chlorides, iodides, nitrates, thiocyanates, perchlorates, and hexafluorophosphates at low concentrations from 10 to 80 mM in the mobile phase. The effect of salts used as mobile phase modifiers was evaluated by comparison of densitograms, peak symmetry coefficients, and theoretical plate numbers. The efficiency of the investigated chromatographic systems depends primarily on the kind of salt and organic solvent in the mobile phase. The best efficiency was obtained by adding ammonium thiocyanate to the mobile phase which contained acetonitrile as an organic modifier.

J. Chromatogr. A 1218 (52), 9406-9413 (2011). Description of a simple, elegant method for the formation of a continuous stationary phase gradient for use in chromatographic separations, at the example of TLC. Gradient stationary phases were formed on activated HPTLC plates using a newly developed methodology termed “controlled rate infusion”. Reaction of the SiOH groups on the activated HPTLC plates with 3-aminopropyltriethoxysilane in a time dependent fashion by using a programmable syringe pump to control the rate of 3-aminopropyltriethoxysilane infusion into the deposition reservoir. The profile of the gradient was controlled by the infusion rate and visualized by the concentration-dependent color reaction of amino groups and ninhydrin. The advantages of such gradients were shown by optimizing the retention and separation of various components in different mixtures of 1) four weak acids and bases and (2) three widely used over-the-counter drugs. The separation was better on gradient stationary phases than on NP-TLC phases or amino phases. The retention and separation can be controlled by strategically modifying the steepness of the gradient.

J. Planar Chromatogr. 29, 72-76 (2016). Pressurized planar electrochromatography (PPEC) of peptides on RP-18 with water – methanol 3:7, an electrical potential of 400 V and a pressure applied of 20 bar. Detection by dipping into 2 % ninhydrin solution in acetone – methanol – glacial acetic acid 25:25:2. The improvement of the PPEC equipment was related to the application of a single Teflon sheet placed beneath both the partition and the cover, resulting in the elimination of the dead volume during the separation process.

J. Chromatogr. A 1575, 91-99 (2018). Presentation of a new prototype for the development of thin-layer chromatograms using flexible mobile phase dosage onto the surface of the layer by moving pipette combined with precise syringe pumps. The pipette is moved by a computer controlled, modified 3D printer mechanism. Delivery of the mobile phase to the layer was equal to or lower than that of conventional development. The chromatograms are developed at optimal mobile phase velocity, which is adjusted to the absorption rate of the layer. As there is no excess eluent on the surface of the layer, a higher performance of the chromatographic system is obtained. By development with constant linear mobile phase velocity, the relationships the plate height vs. mobile phase linear velocity obtained with planar chromatography driven by capillary forces are investigated and reported. Also investigated were the relationships between plate height and mobile phase linear velocity, the influence of the variance of the starting zone related to the total peak variance, and the influence of narrowing the starting zone on the performance of the whole system. There is a significant influence of the starting zone variance on the total peak variance, and therefore of the starting zone size on the plate height of the system.

Abstracts of 1985 Beijing Conference and Exhibition on Instrumental Analysis, 527 (1985). Report of state-of-the-art on instrumental TLC with special emphasis on a new automated multiple development technique employing reproducible elution gradients demonstrated by several application samples. Discussion of the combination of a densitometer with a desktop computer for controlling, data processing and quantitative evaluation.