J. Food Comp. Anal. 48, 25-33 (2016). HPTLC of kavalactones (K, DHM, DHK, M, DMY, Y) and flavokavins (FKA, FKB, FKC) in kava (Piper methysticum) on silica gel with hexane – dioxane 4:1. Individual standards of the following nine compounds of interest were applied on plates and scanned after elution to obtain their UV absorption maxima: flavokavin A (FKA, 361 nm), flavokavin B (FKB, 343 nm), flavokavin C (FKC, 368 nm), kavain (K, 247 nm), dihydromethysticin (DHM, 200 nm), dihydrokavain (DHK, 242 nm), methysticin (M, 306 nm), demethoxyyangonin (DMY, 338 nm), and yangonin (Y, 354 nm). Detection by dipping for 1 s into anisaldehyde – sulfuric acid reagent (10 mL sulfuric acid with 170 mL of ice-cooled methanol, 20 mL of acetic acid, and 1 mL of anisaldehyde reagent), followed by heating at 100 ºC for 3 min. Quality of the samples was assessed by computing two ratios after scanning the plates at 245 nm (kavain/total kavalactones; K/KL) and 366 nm (flavokavins/kavalactones; FK/KL). The ratio K/KL corresponds to the peak area of K versus the sum of the peak areas of all other kavalactones (DHM + DHK + M + DMY + Y). The ratio FK/KL corresponds to the sum of the peak areas of the three FK (A + B + C) versus the peak areas of Y and DMY._x000D_

J. Liq. Chromatogr. Relat. Technol. 39, 312-321 (2016). HPTLC of lupeol in waxes of different cabbage varieties on RP-18 with ethyl acetate – acetonitrile 5:1. Detection by dipping into the anisaldehyde reagent (16 mL sulfuric acid were dropwise added to a cooled mixture of 20 mL glacial acetic acid and 170 mL methanol, then 1 mL of anisaldehyde was added), followed by heating at 110 °C for 30 s. Quantitative determination by absorbance measurement at 535 nm. The hRF of lupeol was 40. Linearity was in the range of 30-150 ng/zone. The LOD and LOQ were 7 and 20 ng/zone, respectively. Intermediate precisions were below 10 %. Recoveries were between 90.3 and 93.1 %.

CBS 114, 9-10 (2015). HPTLC of phosphodiesterase type 5 inhibitors Viagra (sildenafil), Levitra (vardenafil), Cialis (tadalafil) and their analogs (hydroxyacetildenafil, homosildenafil, thiohomosildenafil, acetildenafil, acetaminotadalafil, propoxyphenyl, hydroxyhomosildenafil, hydroxyhomosildenafil, and_x000D_
hydroxythiohomosildenafil) on silica gel with t-butyl methyl ether – methanol – 28 % ammonia 20:2:1 with chamber saturation, migration distance 70 mm. Detection under UV 254 and 366 nm. Densitometric evaluation by absorbance measurement at 232 nm. Identification of the substances based on their hRf values and distinctly different UV spectra.

J. Planar Chromatogr. 29, 330-335 (2016). HPTLC of wedelactone in Eclipta alba, Wedelia calendulacea and Wedelia trilobata on silica gel with toluene – chloroform – ethanol – formic acid 10:8:2:1. Quantitative determination by absorbance measurement at 351 nm. The hRF value for wedelactone was 29. Linearity was between 80 and 280 ng/zone. The intermediate precision was below 2.5 % (n=3). The LOD and LOQ was 0.36 and 1.09 ng/zone, respectively. Recoveries were between 99.4 and 100.3 %.

J. Planar Chromatogr. 29, 429-434 (2016). HPTLC of chlorpyrifos (1) insecticide and its metabolite 3,5,6-trichloropyridinol (2) in visceral samples on silica gel with n-heptane – acetone 1:1. Quantitative determination by absorbance measurement at 300 nm. The hRF values for (1) and (2) were 64 and 54, respectively. Linearities were between 0.5 and 4 μg/zone for (1) and 0.05 and 0.4 μg/zone for (2). The intermediate precisions were below 2.9 % (n=3). The LOQs were 1.5 μg/zone for (1) and 0.15 μg/zone for (2). Recoveries ranged between 84 and 91 % for (1) and 80 and 93 % for (2).

Planta Medica 83(03/04), 239-244 (2017). HPTLC of flavokawin B (purity checked by TLC, followed by sulfuric acid detection) and a hexane maceration of Polygonum ferrugineum aerial parts on silica gel, twice in the same direction with n-hexane – ethyl acetate 4:1 (humidity 33 %). Detection of flavokawin B by densitometry at 366 nm (without derivatization). The hRf value was 53. The content of flavokawin B was 13.6 % in the hexane extract and 1.0 % in the dried plant.

J. Planar Chromatogr. 30, 259-263 (2017). HPTLC of lupenone in the barks of D. melanoxylon on silica gel with n-hexane ‒ ethyl acetate 41:9. Quantitative determination by absorbance measurement at 395 nm. The hRF value for lupenone was 31. Linearity was between 100 and 500 ng/zone. The intermediate precision was <2 % (n=6). LOD and LOQ were 40 and 100 ng/zone. Average recovery rate was 98.7 %.

J. Chromatogr. A 1473, 133-142 (2016). Development of a simple, accurate and precise method for the analysis of proton pump inhibitors and their co-formulated drugs, available as binary combination, by HPTLC on silica gel with toluene – iso-propranol – acetone – ammonia 50:23:25:2. Identification of 14 analytes (except for rabeprazole and lansoprazole which could not be separated) based on hRf and recorded peak spectra. Qantitative determination by densitometry at 290 nm. The linear response for the selected drugs was good with correlation coefficients ≥0.9993. The LOD and LOQ was between 7-160 ng/band and 21-478 ng/band, respectively, for all the analytes. Assessment of the method performance by analyzing different laboratory simulated mixtures and some marketed formulations of the selected drugs, and successful application of the method to investigate potential counterfeit of proton pump inhibitors through a series of simulated formulations with good accuracy and precision.