Planta Medica 84(6/7), 465-474 (2018). The new concept “Comprehensive HPTLC Fingerprinting” was applied to define specifications for the identification and purity assessment of Angelica gigas roots, and for the quantification of its markers: the coumarins decursin and decursinol angelate. Methanolic root extracts of A. gigas (10 reference materials, 24 commercial samples), of 26 other Apiaceae species (including 10 Angelica, 9 Ligusticum, 2 Notopterygium, 4 Peucedanum, and Levisticum officinale) and of mixtures, were developed with toluene - ethyl acetate - acetic acid 90:10:1 on HPTLC silica gel (at 33% relative humidity, chamber pre-saturated for 20 min with filter paper and developing solvent) and dried for 5 min. Detection under white and UV lights before and after derivatization by dipping into 10% sulfuric acid in methanol and then heating 3 min at 100°C. Quantitative evaluation by densitometry in fluorescence mode at UV 313 nm, and luminance was also calculated from the image pixels. The study showed the presence in A. gigas of nodakenin, decursinol, 7-demethylsuberosin, imperatorin, osthole, and isoimperatorin at hRF 0, 4, 15, 33, 38 and 44 respectively. Z-ligustilide (hRF 59) was absent from A. gigas, allowing 1) to distinguish it from several other Apiaceae species; 2) to identify in mixtures with A. gigas two common adulterants (A. acutiloba, A. sinensis) even at 1% in the root powder. Minimal content of A. gigas fingerprint markers (decursin + decursinol acetate, co-eluting at hRF 27) was assessed as 3% (w/w) based on the quantified peaks from A. gigas reference materials.

J. Liq. Chromatogr. Relat. Technol. 42, 563-569 (2019). TLC of 17 new anti-proliferative and antiinflammatory tetracyclic 6-substituted 9-fluoroquinobenzothiazines on RP-18 with acetone - aqueous TRIS (tris(hydroxymethyl)-aminomethane) buffer pH 7.4 (ionic strength 0.2 M), where the concentration of acetone was from 50 to 85 % in 5 % increments. Lipophilicity parameters were determined (R_M0 and logP_TLC) and compared with computationally calculated lipophilic parameters. Relation of lipophilicity with predicted and experimental biological activities was discussed.
 

J. Planar Chromatogr. 32, 517-520 (2019). HPTLC of tramadol (1), caffeine (2), paracetamol (3), ibuprofen (4), naproxen (5), and diclofenac (6) on RP-18 WF, LiChrospher RP-18 WF, and RP-18 WF with concentration zone, developed with various ratios of methanol in water with 0.1 M potassium chloride. Qualitative identification under UV light at 254 nm. Potassium chloride may be used to suppress ion–ion interactions between the solutes and the silica gel surface.  HPTLC RP-18WF plates with concentration zone and developed with methanol - water 13:7 with addition of 0.15 mol/L KCl were suitable for the qualitative and quantitative analyses of tramadol, paracetamol, caffeine, naproxen, and ibuprofen or diclofenac. The method allowed to study subtle differences in the efficiency of the separation of analgesic drugs by HPTLC with similar octadecyl silica-based adsorbents.  

J. Planar Chromatogr. 32, 265-271 (2019). HPTLC of 24 anions on tri-n-butyl amine (TBA) impregnated silica gel with 13 mobile phases (methanol, dimethylformamide, diisopropyl ether, tetrahydrofuran, 2-propanol, dimethylformamide - methanol 1:1, dimethylformamide - diisopropyl ether 1:1, dimethylformamide - tetrahydrofuran, 1:1, dimethylformamide - 2-propanol 1:1, 0.1 M oxalic acid, 0.1 M tartaric acid, 0.1 M citric acid and 0.1 M succinic acid). The retention behavior was analyzed in aqueous and non-aqueous mobile phases. The hRF values were also correlated with their lyotropic numbers. 20 % TBA-impregnated silica gel was found very effective for binary and ternary separations of anions.
 

J. Chromatogr. A 1440, 240-248 (2016). Our previous report showed that RP-18 phases for HPTLC provide complex retention mechanisms based on various polar and nonpolar interactions. Here we show that for the chromatography of peptides, due to mixed-mode properties of these adsorbents, there is a simple way to obtain inversion of a separation system (from reversed-phase to normal-phase, and vice versa). The system inversion leads to a significant change of selectivity, which may be useful in 2D separation of complex samples of basic/amphoteric compounds such as peptides. This results from the fact, that RP-18 phases for HPTLC may be used in hydrophilic interaction chromatography (HILIC) or RP chromatography, depending on the mobile phase composition.

(Studies on the dependence of the chromatographic behaviour on chemical structure for some p-substituted aniline and acetanilide derivatives). TLC of p-chloro-acetanilide, phenacetine, p-phenetidine, p-chloro-aniline, p-(N-acetyl-amino)-phenol on silica with ether. Correlation of structure and chromatographic properties acc. to the Snyder equation.

J.Liquid Chromatogr. 6, 165-177 (1983). TLC of 48 metal ions on silica impregnated with tri-n-butylphosphate, with 1N HCL, 1N HNO3, iN H2S04, 0.1M oxalic acid, 0.1M tartaric acid, 0.1M citric acid.

J. Planar Chromatogr. 3, 322-325 (1990). The linear equation which enables the type of molecular interactions predominating in a chromatographic system to be defined has been investigated using binary mobile phases comprising pairs of solvents with small differences in polarity. The composition of the adsorbent surface was obtained from the excess adsorption isotherme and utilized to analyze the mechanism of the chromatographic separation. TLC system: silica with three different binary mixtures of cyclohexane - benzene, heptane - chloroform, and trichloroethylene - benzene.