J. Sep. Sci. 45, 4187-4197 (2022). HPTLC of tadalafil (1) and canagliflozin (2) in spiked and real human plasma on silica gel with ethyl acetate - toluene - methanol 2:2:1. Quantitative determination by absorbance measurement at 291 nm. The hRF values for (1) and (2) were 73 and 55, respectively. Linearity was between 0.5 and 25 ng/zone for both (1) and (2). Inter-day and intra-day precisions were below 2 % (n=6). The LOD and LOQ were 0.14 and 0.43 ng/zone for (1) and 0.16 and 0.47 ng/zone for (2). Recovery was between 96.1 and 100.7 % for (1) and 97.6 and 102.0 % for (2).

J. Sep. Sci. 46, 2200695 (2023). HPTLC of phloroglucinol (1), trimethylphloroglucinol (2), and the impurity 3,5-dichloroaniline (3) on silica gel with ethyl acetate - butanol - ammonia 40:10:1. Quantitative determination by absorbance measurement at 210 nm. The hRF values for (1) to (3) were 23, 36 and 86. Linearity was between 2 and 12 µg/zone for (1), 1 and 10 µg/zone for (2) and 0.5 and 8 µg/zone for (3). Inter-day and intra-day precisions were below 1 % (n=3). The LOD and LOQ were 410 and 1250 ng/zone for (1), 310 and 940 ng/zone for (2) and 140 and 410 ng/zone for (3). Mean recovery was 98.9 % for (1), 100.7 % for (2) and 99.7 % for (3).

Chinese Medicine 15, 76 (2020). This review compared the 2020 editions of Chinese (ChP) and European Pharmacopoeas (EuP) in different aspects of quality control of traditional Chinese medicinal plants (73 of which drugs were common to both, but with differences in species or organs for 17 of them). Discussed points included history, identification, plant origin and processing, sample preparation, marker selection, tests and assays, as well as advanced analytical techniques for quality control and for the establishment of comprehensive quality standard. TLC was discussed in relation to its following aspects: purposes, markers/references, techniques and result description.
(A) The main uses of TLC and HPTLC were (1) chemical-based identification of the plant in a more accurate and precise method than by macroscopic and microscopic observation only, and in a more direct and easily interpretation than HPLC, and allowing the simultaneous analysis of multiple samples in parallel; (2) control of possible adulterants; (3) quantification of active compounds. Both uses (1) and (2) were combined in some EuP monographs: as example were given the roots of Angelica dahurica, A. pubescens, A. sinensis, using TLC for identification of the species and of adulterants from other species (Angelica, Levisticum and Ligusticum).
(B) In ChP, identification through TLC was in most cases achieved by fingerprint comparison to an official reference extract or herb (herbal reference substance). At the opposite, EuP often indicated analytical markers, irrespective of any pharmacological activity, but chosen only for analytical purposes in TCM identification and quantification. Examples were: aescin and arbutin as analytical markers for TLC identification of Anemarrhena asphodeloides rhizome and Panax notoginseng root.
For the TLC system suitability assessment tests, ChP used the same intensity markers or active markers that were chosen for the identification or assay; whereas EuP often used other specific references, e.g. isoeugenol and methyleugenol in the case of Ophiopogon japonicus roots.
(C) For the techniques, conventional separations and chemical derivatizations were used. Hyphenations of TLC to other analytical methods (e.g. MS) were absent. Only one monograph applied an effect-directed analysis directly on TLC chromatogram (free DPPH• radical scavenging assay for TLC identification of Rehmannia glutinosa root, in ChP).
Sometimes, the TLC methods were different between both reference books for the same species. Example was given for Belamcanda chinensis (=Iris domestica) rhizome: in EuP, development on silica gel with cyclohexane – ethyl acetate – acetic acid 20:80:1, detection under UV 254 nm, comparison to standards coumarin and irisflorentin; whereas in ChP, development on polyamide layer with chloroform – butanone – methanol (3:1:1), detection under UV 365nm after derivatization with aluminium chloride, comparison to a reference rhizome powder.
 (D) Finally, the results in ChP were described as a text stating the similarity of sample profile with the profile of the chosen reference, whereas the results in EuP were described with a schematic box indicating the positions of bands of interest.

J. Sep. Sci. 45, 2582-2590 (2022). HPTLC of favipiravir (1), molnupiravir (2), and ritonavir (3) on silica gel with methylene chloride - ethyl acetate - methanol - 25 % ammonia 6:3:4:1. Quantitative determination by absorbance measurement at 289 nm. The hRF values for (1) to (3) were 22, 42 and 63, respectively. Linearity was between 4 and 100 µg/mL for (1) and (2) and 3 and 100 µg/mL for (2). Inter-day and intra-day precisions were below 2 % (n=5). The LOD and LOQ were 1 and 3 µg/mL for (1) and (2), and 1 and 4 µg/mL for (2). Mean recovery was 99.6 % for (1), 99.5 % for (2) and 99.8 % for (3). 

J. Sep. Sci. 202200754 (2022). HPTLC of canagliflozin (1) and its major degradation product (2); metformin (3) and its major degradation product cyanoguanidine (4), and metformin toxic impurity melamine (5) on silica gel with acetone - ethyl acetate - acetic acid 40:10:1. Quantitative determination by absorbance measurement at 205 nm. The hRF values for (1) to (5) were 21, 35, 47, 71 and 83, respectively. Linearity was between 200 and 3000 ng/zone for (1), 50 and 3000 ng/zone for (2), 50 and 2500 ng/zone for (3), 20 and 2500 ng/zone for (4) and (5). Inter-day and intra-day precisions were below 2 % (n=9). The LOD and LOQ were 17 and 51 ng/zone for (2), 6 and 19 ng/zone for (4) and 3 and 11 ng/zone for (5). Mean recovery was 101.8 % for (1), 100.9 % for (2), 99.4 % for (3), 102.0 % for (4) and 98.4 % for (5). 

J. Sep. Sci. 2200951 (2022). HPTLC of amoxicillin (1), metronidazole (2), and famotidine (3) on silica gel with methanol - chloroform - toluene - water - glacial acetic acid 50:20:15:5:1. Quantitative determination by absorbance measurement at 280 nm for (1) and (3) and 300 nm for (2). The hRF values for (1) to (3) were 42, 81 and 52, respectively. Linearity was between 100 and 1600 ng /zone for (1) and 100 and 900 ng/zone for (2) and (3). Inter-day and intra-day precisions were below 2 % (n=9). The LOD and LOQ were 30 and 100 ng/zone for (1), 20 and 60 ng/zone for (2) and 30 and 90 ng/zone for (2), respectively. Mean recovery was 99.8 % for (1), 100.0 % for (2) and 101.0 % for (3).

J. Sep. Sci. 45, 3800-3810 (2022). HPTLC of favipiravir (1) and meropenem (2) in human plasma on silica gel with ethyl acetate - methanol - water - formic acid 50:40:15:3. Quantitative determination by absorbance measurement at 300 nm for (1) and (2). The hRF values for (1) and (2) were 34 and 10, respectively. Linearity was between 0.1 and 20 µg/mL for (1) and 10 and 60 µg/mL for (2). Inter-day and intra-day precisions were below 5 % (n=3). The LOQ were 0.1 and 10 µg/mL for (1) and (2), respectively. Mean recovery was 99.7 % for (1) and 98.0 % for (2).

J. Sep. Sci. 45, 1616-1635 (2022). HPTLC of gallic acid (1), protocatechuic acid (2), vanillic acid (3), cinnamic acid (4), piperine (5), guggulsterone-E (6), and guggulsterone-Z (7) in Mahayograj Guggul on silica gel with toluene - ethyl acetate - formic acid 10:9:2 for (1) to (3) and toluene - acetone 9:1 for (4) to (7). Quantitative determination by absorbance measurement at 250 nm for (6) and (7), 280 nm for (1), (2), (3) and (4) and 343 nm for (5). The hRF values for (1) to (7) were 30, 41, 47, 15, 33, 41 and 45, respectively. Linearity was between 100 and 1000 µg/mL for (1), 5 and 60 µg/mL for (2), 10 and 80 µg/mL for (3), (4) and (7), 20 and 100 µg/mL for (5) and 40 and 120 µg/mL for (6). Inter-day and intra-day precisions were below 4 % (n=18). The LOD and LOQ were 4 and 14 µg/g for (1), 7 and 21 µg/g for (2), 24 and 72 µg/g for (3), 0.8 and 2.4 µg/g for (4), 12 and 35 µg/g for (5), 2 and 6 µg/g for (6) and 4 and 14 µg/g for (7), respectively. Recovery was between 86.6 and 102.0 % for (1) to (7).