Phytochem. Anal. 28, 87-92 (2017). HPTLC fingerprint of the aerial parts of Justicia secunda on silica gel with chloroform – methanol – water 6:4:1. Detection by dipping into 200 mL enzyme solution (2000 U of alpha-D-glucosidase dissolved in 200 mL buffer solution prepared with 10 g sodium acetate in 250 mL double-distilled water, pH 7.5 with acetic acid), followed by incubation for 1 h in a humid desiccator and dipping into 200 mL of substrate solution (2 mg/mL 2-naphthyl-alpha-D-glucopyranoside in 50 % aqueous ethanol and 2.5 mg/mL Fast blue salt B in double-distilled water, mixed 1:1 before applying). Detection under UV 366 nm.

J. Planar Chromatogr. 30, 488-494 (2017). HPTLC of febuxostat (1) and acetaminophen (2) on silica gel with chloroform – methanol – cyclohexane ‒ 96 % acetic acid 70:10:10:1. Quantitative determination by absorbance measurement at 320 nm for (1) and 250 nm for (2). The hRF values for (1) and (2) were 65 and 46, respectively. Linearity was between 100 and 300 ng/zone for (1) and 50 and 150 ng/zone for (2). LOD and LOQ were 38 and 110 ng/zone for (1) and 16 and 50 ng/zone for (2). The intermediate precision was <2 % (n=6). Recovery ranged from 98.8 to 101.2 % for both (1) and (2).

J. Liq. Chromatogr. Relat. Technol. 41, 315-323 (2018). HPTLC of three types of macrocyclic compounds, i.e. (1) cyclodextrins, (2) calixarenes and (3) macrocyclic antibiotics, on silica gel or RP-18 with different compositions of water – organic liquids (methanol, ethanol, acetonitrile). Detection of (1) on silica gel with a 1:1 mixture of 10 % α-naphthol in ethanol and 10 % sulfuric acid in water, followed by heating at 120 °C for 5-10 min; and on RP18 W by spraying with a 25 % methanolic solution of sulfuric acid, followed by heating at 120 °C for 5-10 min. Detection of (2) by spraying with 20 % aqueous solution of perchloric acid, followed by heating at 120 °C for 5 min. A comprehensive retention data set was obtained for fast selection of mobile phase compositions.

Biochem. Biophys. Res. Commun. 500, 103-109 (2018). 2D-TLC of glycerolipid classes in Arabidopsis thaliana seedlings on silica gel with chloroform – methanol – ammonia 15:10:1 in the first dimension and chloroform – methanol – acetic acid – water 170:20:15:3 in the second dimension. Detection by spraying with 0.01 % primuline in 80 % acetone. Lipid zones were scraped off from the TLC plate and separated lipids were analyzed by gas chromatography.

J. Chromatogr. Sci. 56, 498-509 (2018). Investigation of the analysis of valsartan (VAL) and sacubitril (SAC) in their supramolecular complex (LCZ696), a newly approved remedy for heart failure, along with the SAC-related substance biphenyl methyl pyrrolidinone (BMP). BMP is an intermediate of the SAC synthesis and is a suspected impurity for SAC and/or LCZ696 tablets. HPTLC coupled with a fluorescence detector (FLD) and a diode array detector (DAD) aimed at analyzing BMP at the low level of 3 % in the presence of its parent drug, SAC. HPLC-FLD and HPLC-DAD were used for detection and quantitation of lower BMP concentrations.

J. Planar Chromatogr. 31, 318-326 (2018). HPTLC of quercetin (1), kaempferol (2), and keto-β-boswellic acid (3) in the herbal extracts of Spinacia oleracea and Boswellia serrata on silica gel with hexane ‒ ethyl acetate ‒ glacial acetic acid 30:20:1. Quantitative determination by absorbance measurement at 272 nm. The hRF values for (1) to (3) were 22, 40 and 54, respectively. Linearity ranged between 1500-3500 ng/zone for (1), 200-600 ng/zone for (2) and 1040-3120 ng/zone for (3). LOD and LOQ were 185 and 560 ng/zone for (1), 42 and 125 ng/zone for (2), and 324 and 981 ng/zone for (3), respectively. The intermediate precision was <2 % (n=3). Recovery ranged between 97 and 100 %.

leaves. J. Planar Chromatogr. 31, 377-381 (2018). HPTLC of ursolic acid and β-sitosterol in the leaves of Paederia foetida on silica gel with toluene ‒ ethyl acetate ‒ formic acid 80:20:1. Detection by spraying with anisaldehyde–sulfuric acid reagent, followed by heating at 110 °C for 1 min. Quantitative determination by absorbance measurement at 550 nm. The hRF values for (1) and (2) were 22 and 38, respectively. Linearity was between 100 and 500 ng for (1) and (2). LOD and LOQ were 40 and 121 ng for (1) and 50 and 152 ng for (2). The intermediate precision was <2 % (n=3). Recovery ranged from 97.2 % to 99.2 % for (1) and 98.0 % to 99.2 % for (2).

J. Chromatogr. Sci., 56 (9), 846–852 (2018). Simultaneous determination of theophylline (THP), guaifenesin (GUI) and guaiacol (GUA, a guaifenesin impurity) by HPTLC on silica gel with ethyl acetate – hexane – methanol - ammonia 65:35:10:2. Detection and quantification by densitometry at 275 nm. The hRf values were 13, 35 and 80 for THP, GUI and GUA, respectively. The linearity range was 0.4–2 μg/band for both THP and GUI, and 0.4–1.2 μg/band for GUA. Validation of the proposed method according to ICH guidelines. Statistical comparison of the results with RP-HPLC showed no difference regarding accuracy and precision.