J. Planar Chromatogr. 32, 481-493 (2019). HPTLC of metformin hydrochloride (1) and ursodeoxycholic acid (2) on silica gel with toluene - ethanol - acetone - formic acid 90:40:50:17. Quantitative determination by absorbance measurement at 234 and 700 nm for (1) and (2), respectively. The hRF values for (1) and (2) were 19 and 80, respectively. Linearity was between 5000 and 40000 ng/zone for (1) and 1500 and 12000 ng/zone for (2). Intermediate precision was below 1 % (n=3). The LOD and LOQ were 195 and 592 ng/zone for (1) and 150 and 455 ng/zone for (2), respectively. Recovery rate was 100.5 % for (1) and 99.9 % for (2).

J. Planar Chromatogr. 32, 475-479 (2019). TLC of enantiomers of (RS)-ketorolac on home-made silica gel plates impregnated with L-Tryp (1), L-Val (2), L-Met (3) or L-His (4) with acetonitrile - methanol - water - chloroform 9:5:2:4 for (1), acetonitrile - methanol - water - dichloromethane 6:2:1:1 for (2), acetonitrile - methanol - water - chloroform 5:3:1:1 for (3) and acetonitrile - methanol - water - chloroform 10:4:1:5 for (4), respectively. Detection by exposure to iodine vapors. The hRF values for (S)-(‒)- and (R)-(+)-ketorolac were 36 and 81 for (1), 30 and 79 for (2), 30 and 87 for (3) and 42 and 85 for (4), respectively. LOD was 0.4 μg/mL.

J. Planar Chromatogr. 32, 447-451 (2019). HPTLC of Fritillaria cirrhosa on silica gel with ethyl acetate - methanol - ammonia solution - water 180:20:10:1. Bioautography by dipping into a 0.15 mg/mL solution of substrate Gly-Pro-p-nitroanilide hydrochloride in 50 % of ethanol, followed by ethanol removal in the hood and dipping into a 10 U/L DPP IV enzyme solution in TrisHCl buffer (pH 8.2, 70 mM), followed by incubation at 37°C for 40 min. Detection by dipping into a solution of 0.5 % sodium nitrite in 1.2 M hydrochloric acid, followed by drying slightly for 5 min and dipping into 0.05 % N-(1-naphthyl)ethylenediamine dihydrochloride solution. Further analysis by mass spectrometry using a TLC interface. The hRF value for the dipeptidyl peptidase IV inhibitor was 58.

J. Planar Chromatogr. 32, 467-474 (2019). HPTLC of quercetin in the fresh fruits of Benincasa hispida on silica gel with toluene - ethyl acetate - formic acid 25:20:1. Quantitative determination by absorbance measurement at 262 nm. The hRF value for quercetin was 39. Linearity was between 100 and 1200 ng/zone. Intermediate precision was below 2 % (n=6). The LOD and LOQ were 20 and 60 ng/zone. Recovery rate was 94.3 %.

J. Planar Chromatogr. 32, 501-504 (2019). HPTLC of aspirin (1) and omeprazole (2) on silica gel with ethyl acetate - dichloromethane - glacial acetic acid 80:20:1. Quantitative determination by absorbance measurement at 241 nm. The hRF values for (1) and (2) were 79 and 19, respectively. Linearity was between 160 and 960 ng/zone for (1) and 80 and 480 ng/zone for (2). Intermediate precision was below 1 % (n=3). The LOD and LOQ were 11 and 32 ng/zone for (1) and 3 and 8 ng/zone for (2), respectively. Recovery rate was between 101 and 106 % for both (1) and (2).

J. Planar Chromatogr. 32, 461-465 (2019). HPTLC of betulinic acid (1), oleanolic acid (2) and lupeol (3) on silica gel with benzene - ethyl acetate - formic acid 679:227:94 for (1), n-hexane - ethyl acetate - glacial acetic acid 40:20:1 for (2) and n-hexane - ethyl acetate 4:1 for (3). Detection by spraying with anisaldehyde sulfuric acid, followed by heating at 105-110 ºC for 5-10 min. Quantitative determination by absorbance measurement at 530 nm. The hRF values for (1) to (3) were 79, 46 and 44, respectively. Intermediate precision was below 2 % (n=3).

J. Planar Chromatogr. 32, 517-520 (2019). HPTLC of tramadol (1), caffeine (2), paracetamol (3), ibuprofen (4), naproxen (5), and diclofenac (6) on RP-18 WF, LiChrospher RP-18 WF, and RP-18 WF with concentration zone, developed with various ratios of methanol in water with 0.1 M potassium chloride. Qualitative identification under UV light at 254 nm. Potassium chloride may be used to suppress ion–ion interactions between the solutes and the silica gel surface.  HPTLC RP-18WF plates with concentration zone and developed with methanol - water 13:7 with addition of 0.15 mol/L KCl were suitable for the qualitative and quantitative analyses of tramadol, paracetamol, caffeine, naproxen, and ibuprofen or diclofenac. The method allowed to study subtle differences in the efficiency of the separation of analgesic drugs by HPTLC with similar octadecyl silica-based adsorbents.  

J. Planar Chromatogr. 32, 379-384 (2019). HPTLC of trigonelline (1) and diosgenin (2) in the seeds of Trigonella foenum-graecum L. on silica gel with acetonitrile - water 3:1. Quantitative determination by absorbance measurement at 267 nm for (1) and at 430 nm after derivatization with vanillin - sulfuric acid for (2). The hRF values for (1) and (2) were 29 and 17, respectively. Linearity was between 200 and 1400 ng/zone for (1) and 50 and 300 ng/zone for (2). Intermediate precision was below 2 % (n=6). The LOD and LOQ were 7 and 1 ng/mL for (1) and 7 and 19 ng/mL for (2), respectively. Recovery rate was between 97.8 and 99.1 % for (1) and 98.2 and 99.3 % for (2), respectively.