J. Planar Chromatogr. 34, 307-313 (2021). HPTLC of gallic acid (1), orientin (2) and orientin-2″-O-β-l-galactoside (3) in Chinese medicine antibacterial gels on silica gel with dichloromethane - butanone - methanol - formic acid 60:5:20:6. Quantitative determination by absorbance measurement at 280 nm. The hRF values for (1) to (3) were 37, 51 and 65, respectively. Linearity was between 89 and 785 ng/zone for (1), 82 and 575 ng/zone for (2) and 26 and 209 ng/zone for (3). Intermediate precisions were below 3 % (n=6). Recovery ranged 95.6-103.3 % for (1), 95.4-104.6 % for (2) and 95.1-104.1 % for (3).

Ars. Pharm. 62, 348-357 (2021). HPTLC of gallic acid (1), quercetin (2) and coumarin (3) in the leaves of Sonneratia apetala on silica gel with toluene - ethyl acetate - formic acid 45:30:2. Quantitative determination by absorbance measurement at 280 nm. The hRF values of (1) to (3) were 20, 42 and 51, respectively.

J. Sep. Sci. 44, 3146-3157 (2021). HPTLC of  gallic acid (1), cinnamic acid (2), piperine (3), eugenol (4), and glycyrrhizin (5) in Divya-Swasari-Vati on silica gel with ethyl acetate - toluene - formic acid 10:9:1 for (1) to (4) and ethyl acetate - formic acid - acetic acid - water 100:10:10:23 for (5). Quantitative determination by absorbance measurement at 280 nm for (1), (2) and (4), 343 nm for (3) and 254 nm for (5). The hRF values for (1) to (5) were 31, 64, 53, 70 and 29, respectively. Linearity was between 400 and 800 µg/mL for (1), 5 and 25 µg/mL for (2), 600 and 1400 µg/mL for (3), 400 and 1200 µg/mL for (4) and 100 and 800 µg/mL for (5). Intermediate precision was below 2 % (n=18). The LOD and LOQ were 180 and 560 ng/g for (1), 3 and 10 ng/g for (2), 8 and 26 µg/g for (3), 3 and 11 µg/g for (4) and 300 and 920 ng/g for (5), respectively. Mean recovery was 96.0 % for (1), 92.3 % for (2), 94.2 % for (3), 96.2 % for (4) and 94.6 % for (5). 

J. Ethnopharmacol. 280, 114417 (2021). HPTLC of bergenin (1), epicatechin (2) and gallic acid (3) in the rhizomes of Bergenia ciliata on silica gel with toluene - ethyl acetate - formic acid 3:7:1. Quantitative determination by absorbance measurement at 280 nm. The hRF values of (1) to (3) were 32, 52 and 74, respectively.

Phytochem. Anal. 3093 (2021). HPTLC of hyperforin (1), hypericin (2) and hyperoside (3) in Hypericum species on silica gel with n-hexane - ethyl acetate 4:1 for (1), toluene - chloroform - ethyl acetate - formic acid 80:50:35:6 for (2) and ethyl acetate - formic acid - acetic acid - water 15:2:2:1 for (3). Detection by spraying with a derivatizing reagent (20 mL of sulfuric acid were carefully added to 120 mL methanol and diluted with 200 mL methanol), followed by heating. Quantitative determination by absorbance measurement at 366 nm. The hRF values of (1) to (3) were 49, 35 ad 49, respectively. Linearity was between 0.4 and 1.4 µg/zone for (1), 20 and 100 ng/zone for (2) and 10 and 100 ng /zone for (3). The intermediate precision was below 2 % (n=6) for (1) to (3). The LOD and LOQ were 120 and 400 ng/zone for (1), 6 and 20 ng/zone for (2) and 3 and 10 ng/zone for (3), respectively. Recovery was between 101.0 and 101.2 % for (1), 98.8 and 100.1 % for (2) and 100.4 and 101.4 % for (3).

Food Chem. 346, 128929 (2021). HPTLC of rutin, kaempferol, linarin, isoquercetin, astragalin, avicularin and trans-tiliroside in herbal tea flowers obtained from five Tilia species, namely T. cordata, T. platyphyllos, T. europaea, T. americana, and T. tomentosa on silica gel with tetrahydrofuran - dichloromethane - formic acid - acetic acid - water 9:9:4:2:3. Detection by spraying with 1 % methanolic diphenylboric acid-β-ethylamine ester, followed by heating at 100-105 °C for 2 min. Qualitative identification under UV light at 254 and 366 nm.

Food Chem. 338, 128115 (2020). 2D HPTLC of tangeretin (1), 5-demethyltangeretin (2), nobiletin (3), 3′-demethylnobiletin (4), 4′-demethylnobiletin (5), 3′,4′-didemethylnobiletin (6), 5-demethylnobiletin (7), 5,3′-didemethylnobiletin (8), 5,4′-didemethylnobiletin (9), 5,3′,4′-tridemethylnobiletin (10), naringenin (11), hesperetin (12), naringin (13) and hesperidin (14) on silica gel with dichloromethane - methanol 20:1 containing 1 % acetic acid in the first direction, then the plate was rotated 90° to the right and eluted with petroleum ether - acetone 3:2. The hRF values for (1) to (12) were 53, 62, 46, 36, 38, 18, 57, 48, 51, 27, 43 and 42, respectively. Detection under UV light at 254 and 366 nm and by spraying with 1 % vanillin in ethanol with several drops of concentrated sulfuric acid; or with 3 % iron chloride dissolved in 0.5 M hydrochloric acid solution for compounds with a phenolic hydroxyl group. The LOD for (1) to (14) under 254 nm ranged from 0.5 to 2.5 mM, while 0.1 to 2.5 mM under 366 nm. Quantitative determination by surface-enhanced raman spectroscopy (SERS).

Food Chem. 343, 128400 (2020). HPTLC fingerprint of Citrus bergamia fruits from the islands of Kefalonia, Corfu and R. Calabria on silica gel with chloroform - methanol - water 13:9:3. Qualitative identification under UV light at 280 nm.