J. Liq. Chromatogr. Relat. Technol. 43, 852-862 (2020). HPTLC of diphenylacetamide derivatives on RP-18 with binary mixtures of organic modifier (ethanol, n-propanol, tetrahydrofuran and acetonitrile 36–52 % with 4 % increments). Detection at UV 254 nm. Lipophilicity of examined derivatives was determined. Two multivariate methods, Cluster Analysis, (CA) and Principal Component Analysis, (PCA) were performed to study the compliance of the chromatographic parameters, the standard measure of lipophilicity, the pharmacokinetic predictors and the toxicity parameters of the substances.

J. Planar Chromatogr. 33, 281-291 (2020). HPTLC of Weikangling capsules (a Chinese patent medicine for treating chronic gastritis, containing Paeoniae Radix Alba, Glycyrrhizae Radix et Rhizoma, Bletillae Rhizoma, Notoginseng Radix et Rhizoma, Poria, Corydalis Rhizoma, Sepiae Endoconcha, and Belladonnae Extractum) on silica gel with chloroform - methanol - water 14:5:1. Detection by spraying with 10 % sulfuric acid in alcohol, followed by heating at 105 ºC for 5 min. Qualitative analysis at UV 366 nm.

J. Planar Chromatogr. 33, 523-530 (2020). HPTLC of clonazepam (1), lorazepam (2), alprazolam (3), diazepam (4), furazepam (5), oxazepam (6) and nitrazepam (7) in urine on silica gel with chloroform - glacial acetic acid 9:1. Direct extraction of the substances from the plate into a mass spectrometer. The hRF values for (1) to (7) were 73, 44, 22, 64, 18, 53 and 40, respectively. Linearity was between 0.2 and 0.8 µg/mL. Intermediate precision was below 5 %. LOD was 1 ng/mL for each substance. Average recovery was 67.1 % for (1), 68.9 % for (2), 64.2 % for (3), 73.1 % for (4), 50.7 % for (5), 81.4 % for (6) and 64.4 % for (7).

J. Planar Chromatogr. 33, 501-509 (2020). HPTLC of chloramphenicol (1), dexamethasone sodium phosphate (2) and tetrahydrozoline HCl (3) in the absence or presence of p-nitroacetophenone (4) on silica gel with ethanol - water - ammonia 14:5:1 (method A) and acetonitrile - water - ammonia 20:6:1 (method B). Quantitative determination by absorbance measurement at 242 and 220 nm. The hRF values for (1) to (3) were 76, 65 and 20, respectively, in method A and the hRF values for (1) to (4) were 78, 38, 58 and 87, respectively, in method B. Linearity was 0.1-1.4 µg/zone for (1), 0.2-1.2 µg/zone for (2) and 0.1-0.5 µg/zone for (3) in method A and 0.6-1.8 µg/zone for (1), 0.8-3.2 µg/zone for (2), 0.01-0.1 µg/zone for (3) and 0.3-1.4 µg/zone for (4) in method B. Intermediate precision was below 2 % (n=3). The LOD and LOQ were 30 and 90 ng/zone for (1), 40 and 120 ng/zone for (2) and 20 and 60 ng/zone for (3) in method A and 60 and 180 ng/zone for (1), 130 and 390 ng/zone for (2), 3 and 9 ng/zone for (3) and 70 and 210 ng/zone for (4) in method B. Average recovery was 100.1 % for (1), 100.2 % for (2), 100.6 % for (3) in method A and 100.1 % for (1), 99.9 % for (2) and 100.2 % for (3) in method B.

J. Planar Chromatogr. 33, 511-522 (2020). HPTLC of celecoxib (1) and diacerein (2) on nanosilica gel with n-hexane - ethyl acetate - tetrahydrofuran - glacial acetic acid 35:15:5:4. Quantitative determination by absorbance measurement at 254 nm. The hRF values for (1) and (2) were 59 and 37, respectively. Linearity was between 20 and 320 ng/zone for (1) and 5 and 80 ng/zone for (2). Intermediate precision was below 2 % (n=3). The LOD and LOQ were 7 and 20 ng/zone for (1) and 2 and 5 ng/zone for (2), respectively. Average recovery was 99.9 % for (1) and 99.6 % for (2).

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, 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).