CBS 109, 10-12 (2012). HPTLC of steviol glycosides (stevioside, rebaudioside, dulcoside A, steviolbioside) on silica gel (pre-washed with methanol and dried at 100 °C for 15 min) with ethyl acetate - methanol - acetic acid 3:1:1 over 60 mm. Detection under white light after immersion in ß-naphthol reagent (2 g in 180 mL ethanol with 12 mL 50 % sulfuric acid) and heating at 120 °C for 5 min. Quantitative absorption measurement at 500 nm after derivatization. LOD was 10 ng/band and LOQ 30 ng/zone. Using the calibration curve method the LOQ was reduced to 12 ng/band via peak height and 20 ng/band via peak area. The calculated expected tolerance range over the whole procedure inclusive sample preparation considered recovery rates at 3 different concentration levels (0.02, 0.13, and 0.20 %) in milk-based matrix. The accuracy (recovery tolerance limit of 92-120 %), repeatability (3.1-5.4 %) and intermediate precision (4.0-8.4 %) were highly satisfying, exemplarily shown for stevioside in milk-based matrix. ANOVA was successfully passed to prove the working range. With the newly developed and validated HPTLC method, steviol glycosides in Stevia leaves, Stevia formulations, and food products were investigated.

J. Liq. Chromatogr. Relat. Technol. 36, 1528-1539 (2013). HPTLC of mebeverine hydrochloride (1), metronidazole benzoate (2), diloxanide furoate (3) and metronidazole (4) in pharmaceutical suspensions on silica gel with hexane - acetone - triethylamine 35:15:3. Quantitative determination by absorbance measurement at 254 nm. The hRf values of compounds (1) to (4) were 10, 34, 49 and 64, respectively. Linearity was 0.4-2.4 µg/zone for (1), 0.3-2.0 µg/zone for (2) and 0.4-2.4 µg/zone for both (3) and (4). Intermediate precision was below 1.2 %. Recovery (by standard addition) was 99.9-100.1 % for compounds (1) to (4). Comparable results were obtained when compared with reported RP-HPLC methods.

Chinese J. of Lishizhen Trad. Med. & Pharm. 23 (7), 1822-1823 (2012). Dannangyan compound oral liquid is a herbal TCM preparation for treating cholecystitis and cholelithiasis. For identification, TLC on silica gel 1) for Radix et Rhizoma Rhei, with the upper phase of petroleum ether (30-60 ºC) – ethyl acetate – formic acid 15:5:1, detection at UV 366 nm and by exposure to iodine vapors and viewing in daylight; 2) for Cortex Magnoliae officinalis, with chloroform – benzene – ethyl acetate 10:4:1, detection by spraying with 5 % vanillin in sulfuric acid - ethanol 1:200 followed by heating at 105 °C for 5 min and viewing in daylight.

J. Liq. Chromatogr. Relat. Technol. 36, 167-179 (2013). HPTLC of darunavir in rat plasma on silica gel with toluene - acetone - methanol 3:1:1. Quantitative determination by mass spectrometry in the ESI+ mode and absorbance measurement at 254 nm. The hRf value of darunavir was 53. Linearity was in the range of 5-150 ng/µL. LOD and LOQ were found to be 1.2 and 3.9 ng/µL, respectively. Intermediate precision was below 2.7 %. Recovery (by standard addition) was 94.8-98.4 %. The recovery of the drug is improved compared with the HPLC method (96.7 %).

J. Planar Chromatogr. 26, 386-394 (2013). Review of the role of TLC chambers in planar chromatography, and the merits of S-chambers in terms of reproducibility and higher peak resolution, allowing to implement 30 % faster separation and 20-30 % higher efficiency compared with unsaturated N-chamber.

Food Chem. 151, 554-560 (2014). HPTLC of flavokavins A, B and C in the roots of kava (Piper methysticum) on silica gel with hexane - dioxane 4:1. Identification by absorbance measurement at 366 nm. Ratios between flavokavins (FKA, B, C) and kavalactones allowed an unambiguous identification of the cultivar noble kava and exclusion of two-days kava in exported material.

J. Liq. Chromatogr. Relat. Technol. 36, 2405-2421 (2013). HPTLC of acetylsalicylic acid (1), caffeine (2), and ethoxybenzamide (3) in combined tablets on silica gel with n-hexane - acetone - glacial acetic acid 7:2:1. Quantitative determination by absorbance measurement at 200 nm for (1), 275 nm for (2) and 300 nm for (3). The hRf values for (1) to (3) were 44, 29 and 59, respectively. Linearity was in the range of 1.7-15.4 µg/zone for (1), 0.6-4.0 µg/zone for (2) and 1.2-8.0 µg/zone for (3). LOD and LOQ were 130 and 390 ng/zone for (1), 25 and 80 ng/zone for (2) and 60 and 180 for (3), respectively. Recoveries (by standard addition) were in the range of 99-100 %. Intermediate intra- and inter-day precision was below 2 % (n=3).

J. Chil. Chem. Soc. 58, 1663-1666 (2013). HPTLC of rosiglitazone (1) and glimepiride (2) in tablet dosage form on silica gel with methanol - toluene - ethyl acetate 1:8:1. Quantitative determination by absorbance measurement at 228 nm. The hRf values for (1) and (2) were 39 and 20, respectively. Linearity was in the range of 100-1500 ng/zone for (1) and 100-1500 ng/zone for (2). LOD and LOQ were 30 and 35 ng/zone for (1) and 85 and 90 ng/zone for (2), respectively. Recovery was 96 % for (1) and (2). Intermediate intra- and inter-day precision was below 2 % (n=6).