J. Liq. Chromatogr. Relat. Technol. https://doi.org/10.1080/10826076.2021.1939046 (2021). HPTLC of picroside-I (1), andrographolide (2) and silybin (3) in Picrorhiza kurroa (roots), Andrographis paniculata (aerial parts) and Silybum marianum (seeds), respectively, on silica gel with n-butanol - glacial acetic acid - water 6:1:3. Quantitative determination by absorbance measurement at 254 nm. The hRF values for (1) to (3) were 49, 68 and 89, respectively. Linearity was between 60 and 600 ng/zone for (1) to (3). The intermediate precision was below 2 %. The LOD and LOQ were 15 and 45 ng/zone for (1), 22 and 67 ng/zone for (2) and 26 and 78 ng/zone for (3), respectively. Recovery was between 99.7 and 103.7 % for (1), 99.7 and 101.1 % for (2) and 99.0 and 101.7 % for (3).

J. Food. Sci. 81, 1378-1384 (2016). HPTLC of Lycium barbarum samples on silica gel with n-butanol - acetic acid - water 15:8:6. DPPH bioautography assay by spraying with 0.04 % 2,2-diphenyl-1-picrylhydrazyl in methanol under dark conditions. Detection under UV light at 535 nm. 

Anal. Bioanal. Chem. 412, 2633-2644 (2020). HPTLC of  cannabinol in sediment samples on silica gel with n-heptane - diethyl ether 9:1. Detection by spraying with cerium- molybdenum reagent (400 mg cerium IV sulfate and 20 g ammonium molybdate in 400 mL 10 % sulfuric acid). HPTLC plates were further analyzed by electrospray ionization mass spectrometry. The hRF value for cannabinol was 20. Linearity was between 25 and 155 ng/zone. Intermediate precision was below 5 % (n=3). The LOD and LOQ were 6 and 21 ng/zone. Average recovery was 73 %.

J. Planar Chromatogr. 34, 55-60 (2021). TLC of genistein‑7‑O‑[α‑rhamnopyranosyl‑(1 → 6)]‑β‑glucopyranoside (GTG) in Derris scandens on silica gel with ethyl acetate - methanol - water 80:13:10. Quantitative determination by absorbance measurement at 254 nm for (1), 256 nm for (2), 300 nm for (3) and 296 nm for (4). The hRF value for GTG was 26. Linearity was between 8 and 120 µg/mL. Intermediate precision was below 2 % (n=3). The LOD and LOQ were 3 and 9 µg/mL. Recovery was between 102.3 and 108.6 %. The results obtained from the TLC–densitometric, TLC–image analysis and HPLC methods were comparable.

J. Planar Chromatogr. 34, 31-38 (2021). HPTLC of reserpine (1), scopoletine (2), piperine (3), bacoside A (4) and lupeol (5) in a polyherbal formulation (containing Rauwolfia serpentina, Nardostachys jatamansi, Convolvulus pluricaulis, Bacopa monnieri, Piper longum) on silica gel with benzene - ethyl acetate - glacial acetic acid - n-butanol 57:30:10:3 for (1), (2) and (3), n-butanol - glacial acetic acid - water 18:3:4 for (4) and benzene - ethyl acetate 9:1 for (5). Detection by spraying with 5 % methanolic sulfuric acid solution, followed by heating at 80 °C for 20 min. Quantitative determination by absorbance measurement at 254 nm for (1) to (3), 598 nm for (4) and 580 nm for (5). The hRF values for (1) to (5) were 17, 53, 73, 34 and 48, respectively. Linearity was between 1 and 2 µg/zone for (1), 2.5 and 4.5 µg/zone for (2), 10 and 50 µg/zone for (3), 12 and 24 µg/zone for (4) and 1 and 5 µg/zone for (5). Intermediate precision was below 2 % (n=6). The LOD and LOQ were 6 and 20 ng/zone for (1), 13 and 38 ng/zone for (2), 11 and 33 ng/zone for (3), 377 and 1143 ng/zone for (4) and 324 and 982 ng/zone for (5), respectively. Average recovery was 98.1 %for (1), 99.9 % for (2), 99.9 for (3), 99.7 % for (4) and 99.5 % for (5).

Planta Med. 85(2), 112-117 (2019). A fraction of an ethanolic extract of Dolichos trilobus roots (Fabaceae) was eluted on a silica gel column with different mixtures of petroleum ether and acetone. This fractionation was monitored by TLC on silica gel (eluent not given), derivatization by spraying with sulfuric acid 10 % (in ethanol) and heating (100 °C). Further isolation steps allowed the identification of eight coumestans in two subfractions: dolichosins A–D, isosojagol, phaseol, psoralidin, dehydroisopsoralidin.

J Pharm Bioallied Sci. 12(2), 139-145 (2020). An HPTLC method was validated for the fingerprint of flavonoids and other phenolic compounds (rutin, apigenin, luteolin, caffeic acid, chlorogenic acid, rosmarinic acid) in methanol macerates of dried aerial parts of five Lamiaceae (subfamily Nepetoideae: Dracocephalum moldavica, Lophanthus anisatus, Monarda fistulosa, Ocimum americanum, Satureja hortensis). HPTLC of extracts and standards on silica gel with chloroform – ethyl acetate – formic acid 5:4:1 or with ethyl acetate – formic acid – water 15:1:1. Detection under UV light before and after spraying with aluminium chloride 1 % in methanol. Rosmarinic acid was present and abundant in all extracts and was also quantified by densitometry at UV 366 nm without derivatization. The LOD was 29.2 µg/mL; the rosmarinic acid concentration range was between 12.6 mg/g (Lophanthus) and 24.8 mg/g (Dracocephalum).

J Am Soc Mass Spectrom 31(9), 1981-1993 (2020). Low-temperature plasma-mass spectrometry was studied for comparison between direct desorption (DD) and diode laser assisted desorption (LD) in terms of quantitative and qualitative analysis of compounds from cellulose vs. silica gel TLC layers. Compounds (the 20 common amino acids, propofol, nicotine, cotinine, salicylamide, acetylsalicylic acid, paracetamol, caffeine, valprolactone and its isomer 4-ene-valproic acid) were applied on the TLC plates (without development) at different concentrations; a commercial mixture of acetylsalicylic acid, paracetamol and caffeine was also applied on TLC plates, developed with dichloromethane – ethyl acetate 1:50, detection at UV 254 nm and quantitative MS. In general, DD provided good results on cellulose, where LODs where between 0.01 and 2.55 ng/mm2, whereas several compounds remained undetected on silica gel. LD however provided LODs on silica gel from 0.3 to 84 pg/mm2. Tandem MS with collision-induced dissociation was implemented to improve signals, LODs and to characterize the other analytical figures-of-merits (including detection of the main fragment ions, determination of optimal laser beam width and irradiance depending on the compounds). For the two metabolites of valproic acid, the ions and fragments had identical values; therefore, a mix of the two isomers had to be applied and separated with dichloromethane – methanol 50:1 before MS; one half of the plate was visualized for control by dipping into potassium permanganate reagent (7.5g KMnO4, 50g K2CO3, 0.75g NaOH in 1L water).