J. Planar Chromatogr. 33, 381-390 (2020). HPTLC of riociguat in tablets on silica gel with ethyl acetate - methanol - glacial acetic acid 80:20:3. Quantitative determination by fluorescence measurement at 300/>465 nm. The hRF value for riociguat was 59. Linearity was between 5 and 25 ng/zone. Intermediate precision was below 2 % (n=3). The LOD and LOQ were 3.4 and 10.2 ng/zone, respectively. Recovery was between 98.7 and 99.1 %. The method was compared with spectrofluorimetric and UV-spectrophotometric methods.

J. Planar Chromatogr. 33, 353-364 (2020). HPTLC of friedelin (1), methylputranjate (2), putrone (3), roxburghonic acid (4), putranjivadione (5), and roxburghonol (6) in the bark of the plant Putranjiva roxburghii on silica gel with n-hexane - ethyl acetate 9:1. Detection by dipping into perchloric acid reagent (50 mL 70% perchloric acid in 50 mL acetone), followed by heating at 110-120 ºC for 5 min. Quantitative determination by absorbance measurement at 570 nm. The hRF values for (1) to (6) were 79, 46, 36, 31, 25 and 21, respectively. Linearity was between 1 and 5 µg/zone for (1) to (6). Intermediate precision was below 2 % (n=3). The LOD and LOQ were 780 and 2600 ng/zone for (1), 210 and 700 ng/zone for (2), 170 and 570 ng/zone for (3), 350 and 1170 ng/zone for (4), 460 and 1530 ng/zone for (5) and 380 and 1270 ng/zone for (6), respectively. Average recovery was 98.0 % for (1), 99.1 % for (2), 97.6 % for (3), 98.9 % for (4), 98.7 % for both (5) and (6).

J. Planar Chromatogr. 33, 413-418 (2020). HPTLC of metanil yellow in colored sweets on silica gel with ethyl acetate - methanol - 25 % ammonia - water 35:11:5:5. Detection at UV 430 nm. The hRF value for metanil yellow was 56.

J. Planar Chromatogr. 33, 341-352 (2020). Review of TLC and HPTLC methods for the analysis of mangiferin in plant sources and formulations. Qualitative and quantitative TLC methods as well as bioanalytical and bioautographical methods were reviewed.   

J. Planar Chromatogr. 33, 329-340 (2020). Review of analysis of heavy metal ions by TLC, including micellar, soil and reversed-phase TLC between 2000 and 2019. The review highlighted the better performance of micellar TLC and the use of cationic and anionic surfactants.

J. Planar Chromatogr. 33, 397-404 (2020). HPTLC of ephedrine on silica gel with n-butyl acetate - acetone - 1-butanol - 5 M ammonia - methanol 4:2:2:1:1. Detection at UV 254 nm. The separated zones eluted directly from the plate into an MS. The ionization mode was selected as electrospray ionization (ESI). The hRF value for ephedrine was 41.

J. Planar Chromatogr. 33, 391-396 (2020). HPTLC of duloxetine hydrochloride (1) and 1-naphthol (2) on silica gel with chloroform - ethyl acetate - benzene - 33 % ammonia solution 60:30:10:1. Quantitative determination by absorbance measurement at 233 nm. The hRF values for (1) and (2) were 15 and 8, respectively. Linearity was between 200 and 1400 ng/zone for (1) and 60 and 540 ng/zone for (2). Intermediate precision was below 2 %. The LOD and LOQ were 23 and 71 ng/zone for (1) and 15 and 47 ng/zone for (2), respectively. Average recovery was 98.8 % for (1) and 99.6 % for (2).

J. Planar Chromatogr. 33, 365-370 (2020). HPTLC of lupeol (1) and β-sitosterol (2) in the stem bark of Crataeva nurvala on silica gel with toluene - methanol 24:1. Detection by spraying with 1 % anisaldehyde - sulfuric acid reagent, followed by heating at 110 ºC. Quantitative determination by absorbance measurement at 545 nm. The hRF values for (1) and (2) were 48 and 34, respectively. Linearity was between 2 and 6 µg/zone for both (1) and (2). Intermediate precision was below 2 % (n=3). The LOD and LOQ were 43 and 133 ng/zone for (1) and 57 and 173 ng/zone for (2), respectively. Average recovery was 98.6 % for (1) and 98.1 % for (2).