J. of Chromatogr. Sci. 58 (5), 418 - 426 (2020). Development of a method for the quantitation of glibenclamide (GLIBEN), rosiglitazone maleate (ROSI) and metformin hydrochloride (MET) from a combined dosage form by HPTLC on RP-18 F254s aluminum layer with methanol - tetrahydrofuran - water - glacial acetic acid 40:9:10:1. Detection under UV light. The hRf for GLIBEN, ROSI and MET was 54, 62 and 80, respectively. Quantification and photodocumentation by densitometry. For GLIBEN and  ROSI the LOD and LOQ was 80 and 200 ng/zone, for MET the LOD and LOQ was 48 and 120 ng/zone, respectively. The linearity for GLIBEN and ROSI was 200 - 1000 ng/zone (r = 0.9991 for GLIBEN and r = 0.9993 for ROSI) and for MET 120 - 600 ng/zone (r = 0.9988). The method was precise and accurate for all three drugs, and well suitable for the analysis of triglucored tablets, and reliable quality control for GLIBEN, ROSI and MET in a combined dosage form.

J. of Chromatogr. Sci. 58 (4), 303 - 308 (2020). Determination of dapoxetine hydrochloride (DAP) and tadalafil (TAD) in their binary mixtures either as raw materials or in pharmaceutical formulations, by HPTLC on silica gel with ethanol - ethyl acetate 1:9. Quantitative determination by densitometry at 222 nm. The linear range was 0.1 - 1.6 and 0.2 - 2.5 μg/band for dapoxetine and tadalafil, respectively, with accuracies of 98.9 % ± 0.6 and 99.3 6% ± 1.4, respectively.

J. of Chromatogr. Sci. 58 (1), 16 - 21 (2020). Development of a selective and sensitive method for the simultaneous determination of a new combination of quinfamide and mebendazole in bulk powder and in pharmaceutical formulation by HPTLC on silica gel with methanol - toluene 1:3. Quantitative determination by densitometry at 254 nm. Validation of the method according to ICH guidelines. Successful application for determination of quinfamide and mebendazole in tablets. Statistical comparison between the developed HPTLC method and a reported simultaneous equation spectrophotometric method showed no significant difference, proving the suitability for quality control testing of the studied drugs.

J. of Chromatogr. Sci. 57 (9), 799 - 805 (2019). Description of a method for the quantification of R, R-glycopyrronium bromide (GLY) and its related impurities in drug substance and drug product by HPTLC on silica gel with dichloromethane - methanol - formic acid 20:1:1. GLY and its related impurities (glycopyrronium impurity G and glycopyrronium impurity J) were separated with hRf values of 17, 34 and 69, respectively. Quantitative determination at 220 nm in the range of 0.3 - 10 and 0.2 - 4.0 μg/zone. The LOD and LOQ were 0.1, 0.3 and 0.05, 0.2 μg/zone for GLY and its related impurities, respectively. The recovery was 99.5 ± 1.4, 100.0 ± 1.3 and 99.6 ± 0.8 and R2 ≥ 0.9968 for GLY and its impurities, consecutively.

J. of Chromatogr. Sci. 57 (6), 552-559 (2019). Analysis of chlorpheniramine maleate (CM), phenylephrine (PE) and guaifenesin (GF) in their mixture and in presence of the GF related substance guaiacol (GL) and the cough syrup preservative sodium benzoate (NaB) by TLC on silica gel with ethyl acetate - methanol - toluene - ammonia 14:3:2:1. Quantitative determination by absorbance measurement at 270 nm. The method was suitable for the determination of CM, PE, and GF in pure powder and in combined cough syrup without interference from the excipients.

Planta Medica 84(11), 813-819 (2018). Fluorinated analogues of epigallocatechin-gallate were purified after synthesis by extraction with ethyl acetate from the synthesis mixtures, followed by column chromatography or (for two pairs of isomers) by preparative TLC. This isolation (as well as monitoring of column elution for the other compounds) was performed by TLC on silica gel with mixtures of n-hexane and (less) ethyl acetate in several concentrations, allowing the separation of diastereoisomers (RF values and yields are given). No derivatisation, visualisation because of fluorescing agent in the layers. Structures were identified by NMR and HR-MS, but apart from the TLC.

J. Liq. Chromatogr. Relat. Technol. 43, 852-862 (2020). HPTLC of diphenylacetamide derivatives on RP-18 with binary mixtures of organic modifier (ethanol, n-propanol, tetrahydrofuran and acetonitrile 36–52 % with 4 % increments). Detection at UV 254 nm. Lipophilicity of examined derivatives was determined. Two multivariate methods, Cluster Analysis, (CA) and Principal Component Analysis, (PCA) were performed to study the compliance of the chromatographic parameters, the standard measure of lipophilicity, the pharmacokinetic predictors and the toxicity parameters of the substances.

J. Planar Chromatogr. 33, 523-530 (2020). HPTLC of clonazepam (1), lorazepam (2), alprazolam (3), diazepam (4), furazepam (5), oxazepam (6) and nitrazepam (7) in urine on silica gel with chloroform - glacial acetic acid 9:1. Direct extraction of the substances from the plate into a mass spectrometer. The hRF values for (1) to (7) were 73, 44, 22, 64, 18, 53 and 40, respectively. Linearity was between 0.2 and 0.8 µg/mL. Intermediate precision was below 5 %. LOD was 1 ng/mL for each substance. Average recovery was 67.1 % for (1), 68.9 % for (2), 64.2 % for (3), 73.1 % for (4), 50.7 % for (5), 81.4 % for (6) and 64.4 % for (7).