J. Planar Chromatogr. 33, 231-244 (2020). HPTLC of apremilast on silica gel with toluene - methanol - ethyl acetate 7:2:1. Quantitative determination by absorbance measurement at 241 nm. The hRF value for apremilast was 63. Linearity was between 200 and 1000 ng/zone. Inter-day and intra-day precision were below 1 % (n=3). The LOD and LOQ were 4 and 13 ng, respectively. Recovery rate was between 99.7 and 100.0 %. Apremilast was subjected to acidic, alkaline, oxidative, dry heat, neutral, and photolytic degradation conditions. The method was implemented using a quality risk management and quality by design approach for regulatory requirements.

Phcog. Mag. 15, 440-448 (2019). HPTLC fingerprint of Psidium guajava on silica gel with toluene - ethyl acetate - formic acid 6:3:1. Qualitative determination under UV light at 254 and 450 nm. The hR_F values of common metabolites were 3, 18 and 42 in both aqueous and n‑butanol fractions.

Pharmacogn. Mag. 15, 256-260 (2019). HPTLC of piperine (1), asiaticoside (2), and withanolide A (3) in a polyherbal formulation of Piper longum, Centella asiatica, and Withania somnifera on silica gel with toluene - ethyl acetate 9:1 for (1), ethyl acetate - methanol - water 20:5:2 for (2) and toluene - ethyl acetate - formic acid 5:5:1 for (3). Detection by spraying with 5 % aqueous sulfuric acid, followed by heating at 110 °C. The developed plates were scanned at 254 nm, 366 nm and visible light. The hR_F values for (1) to (3) were 24, 71 and 77, respectively.

J. Sep. Sci. 43, 1195-1202 (2020). HPTLC of norfloxacin (1) and tinidazole (2) on RP silica gel with 30 % trifluoroacetic acid. Detection under UV 254 and 366 nm, documentation with a smartphone camera. The hR_F values for (1) and (2) were 6 and 31, respectively. Linearity was between 0.06 and 6 µg/zone for (1) and 0.09 and 9 µg/zone for (2). Intermediate precisions were below 2 % (n=3). The LOD and LOQ were 0.01 and 0.03 µg/zone for both (1) and (2).

J. Sep. Sci. 43, 2228-2239 (2020). HPTLC of binary mixtures of tenofivir disoprixil fumarate (1) / lamivudine (2) and lamivudine (2) / zidovudine (3) on silica gel with dichloromethane - acetonitrile - methanol - ammonia 67:20:10:3. Quantitative determination by absorbance measurement at 272 nm. The hR_F values for (1) to (3) were 43. 79 and 81, respectively. Linearity was in the range of 5-40 µg/mL for (1), 2-16 µg/mL for (2) and 1-16 µg/mL for (3). Intermediate precisions were below 2 % (n=3). The LOD and LOQ were 1 and 3 µg/mL for (1), 1 and 4 µg/mL for (2) and 2 and 6 µg/mL for (3), respectively. Recovery was between 96.5 and 101.8 % for (1) to (3).

J. Sep. Sci. 43, 2330-2337 (2020). HPTLC of metoclopramide (1), ergotamine (2), caffeine (3), and paracetamol (4) on silica gel with ethyl acetate - ethanol - ammonia 90:10:1. Quantitative determination by absorbance measurement at 272 nm. The hR_F values for (1) to (4) were 14, 36, 49 and 74, respectively. Linearity was in the range of 1-24 µg/zone for (1), 0.1-6.5 µg/zone for (2), 0.8-3.5 µg/zone for (3) and 0.8-10 µg/zone for (4), respectively. Intermediate precisions were below 2 % (n=9). The LOD and LOQ were 336 and 1017 ng/zone for (1), 43 and 130 ng/zone for (2), 265 and 802 ng/zone for (3) and 262 and 793 ng/zone for (4). Average recovery was 99.7 % for (1), 100.6 % for (2), 100.1 % for (3) and 100.2 % for (4).

J. Liq. Chromatogr. Relat. Technol. 43, 414-423 (2020). HPTLC fingerprint of Ganoderma lucidum fruiting body on silica gel with toluene - tetrahydrofuran - acetic acid 70:30:1. Detection by dipping into a solution of 10% sulfuric acid in methanol, followed by heating at 100 ºC for 3 min. Qualitative determination under UV light at 254 and 366 nm. The hRF values for ganoderic acids D, B, A, G and C2 were in the zone between 10 and 50. This zone was used for quantification of total triterpene acids by absorbance measurement at 260 nm. Linearity of each of the main peaks between hRF 10 to 50 was determined. The linear range of ganoderic acid A was between 200 and 500 ng/zone.  The study proposes a new method for evaluation, based on “comprehensive high-performance thin layer chromatography (HPTLC) fingerprinting.” Instead of several different methods using different chromatographic techniques, a single HPTLC analysis for identification of Ganoderma lucidum fruiting body with a test for adulteration and quantitative determination of the content of total triterpene acids is proposed. As an alternative to the current tests in the  USP monograph on G. lucidum fruiting body this HPTLC method is a single, low-cost test, which eliminates the UHPLC assay of total triterpene acids.

J. Liq. Chromatogr. Relat. Technol. 43, 445-454 (2020). HPTLC of aniline (1), 2,4-xylidine (2) and 4-aminoazobenzene (3) in chili oils, pickles and related food matrices on silica gel with chloroform - acetic acid 9:1. Quantitative determination by absorbance measurement at 280 nm. The hR_F values for (1) to (3) were 53, 43 and 82, respectively. Linearity was in the range of 2-14 ppm for (1) to (3). The LOD and LOQ were 0.0015 and 0.0045 ppm for (1), 400 and 1200 ppm for (2) and 200 and 600 ppm for (3), respectively. Mean recovery rate was 100.2 % for (1) and 100.9 % for (2). The azo aryl amines were also analyzed using a TLC-MS interface.