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.

J. Planar Chromatogr. 32, 359-364 (2019). HPTLC of Schizonepeta annua on silica gel with chloroform - toluene - acetic acid 600:100:3. Detection by spraying with 5 % vanillin - sulfuric acid reagent (mixture of 2.5 g vanillin, 45 mL ethanol, and 5 mL concentrated sulfuric acid), followed by heating at 105 °C for 5 min. Antibacterial assay was performed by dipping the plate into a cell suspension culture (Brain heart infusion broth and brain heart infusion agar in the ratio of 9:1), followed by incubation at 35 °C for 16 h and immersion into 0.2 % MTT solution for 3s, followed by incubation at 35 °C for 3h. Plates were scanned at 546 nm. The hRF values for thymol and carvacol were 88 and 78, respectively.

J. Planar Chromatogr. 32, 393-400 (2019). HPTLC of quercetin (1) and resveratrol (2) on silica gel with toluene - ethyl acetate - formic acid 12:5:3. Quantitative determination by absorbance measurement at 286 nm. The hRF values for (1) and (2) were 41 and 46, respectively. Linearity was between 50 and 2000 ng/zone for both (1) and (2).  Intermediate precision was below 2 % (n=3). The LOD and LOQ were 27 and 122 ng/zone for (1) and 83 and 370 ng/zone for (2), respectively. Recovery rate was between 99.6 and 101.9 % for (1) and (2).

J. Planar Chromatogr. 32, 385-392 (2019). HPTLC of lupeol in formulations on silica gel with toluene - ethyl acetate 237:13. Detection by dipping into anisaldehyde–sulfuric acid reagent, followed by heating at 110 ºC for 10 min. Quantitative determination by absorbance measurement at 600 nm. The hRF value for lupeol was 42. Linearity was between 500 and 3000 ng/zone. Intermediate precision was below 1 % (n=3). The LOD and LOQ were 7 and 21 ng/zone, respectively. Recovery rate was between 99.5 and 101.5 %.