J. Chromatogr. Sci. 54 (4), 609-617 (2016). HPTLC of sulbutiamine (SUL) in the presence of different degradation products after subjecting the drug to stress conditions (according to ICH: neutral, alkaline and acidic hydrolysis, oxidation, photodegradation and dry heat degradation), on silica gel aluminum foil with acetone – methylene chloride – ammonia buffer (pH 8.5±0.2) 14:6:1. Densitometric evaluation at 254 nm. The calibration curve was between 0.4–5.0 µg/zone with good correlation coefficients. The LOD and LOQ were 110 and 330 ng/zone, respectively. Structure elucidation of the resulting degradation products by ESI-MS/MS. The results showed that the drug was completely degraded with 0.1 N NaOH, 1 N HCl and 30 % hydrogen peroxide, while it was partially degraded by 0.1 N HCl, 3 % hydrogen peroxide and UV light. The hRf of SUL was 46 and the zone was completely separated from all obtained degradation products.

J. Chromatogr. A 1515, 232-244 (2017). Characterization of lipids in both bone marrow (BM) and mineralized tissue (MT) compartments, and their potential implication in bone pathologies, involving sample preparation, lipid extraction and analytical issues using a small sample size (≤ 0.5 g of rat femurs). Two major issues in bone handling were addressed with two cleaning steps after BM removal and by adding a demineralization step to the overall lipid extraction protocol, to avoid potential contamination of the MT by marrow lipids and the poor accessibility of certain lipids from the MT. HPTLC of the major neutral and polar lipids provided excellent resolution for 15 standards, good precision (inter-day %RSD <13 %) and recoveries of the standards ranged between 76 and 122 %. The method was suitable for lipid determination in both BM and MT and reliable in terms of lipid quantification. Demineralization facilitates phosphatidylserine and cholesterol ester extractions from the MT. Confirmation of the HPTLC data by HPLC determination of fatty acids as naphthacyl esters in bone samples. The mineralized tissue seems to be more metabolically active than the bone marrow.

J. Planar Chromatogr. 30, 363-374 (2017). HPTLC of acetylsalicylic acid (1) and its related compound salicylic acid (2) on silica gel with n-hexane – diethyl ether – 80 % acetic acid 7:2:1. Good quality densitograms with well separated and symmetric peaks of (1) and (2) were achieved. Detection with the following reagents: Janus blue, bromophenol blue, bromocresol blue, hydrogen peroxide (without heating and with heating to 90 °C during 60 min), 1 % sodium hydroxide (with heating to 45 °C and also with heating to 90 °C during 60 min), brilliant green, malachite green, and thymol blue.

Phytochem. Anal. 28, 125-131 (2017). HPTLC of the dried fractions of Morus alba wood on silica gel with dichloromethane – methanol 22:3, and to achieve better resolution for the high activity fractions with dichloromethane – methanol 83:17. Qualitative determination under UV 254 and 366 nm and detection with sulfuric acid reagent. Partial least squares-regression was performed to discover the substances that were most correlated to bioactivity.

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.

J. Chromatogr. A 1533, 208-212 (2018). Development of a rapid method for the determination of caffeine, theobromine and theophylline in Mate beer and Mate soft drinks. Sample preparation through filtration followed by degassing, dilution with acetonitrile in the case of Mate beers for protein precipitation and centrifugation. HPTLC of the extracts on silica gel with acetone – toluene – chloroform 4:3:3, detection and quantification by densitometry at UV 274 nm. The LOD and LOQ were 1 and 4 ng/zone for caffeine, theobromine and theophylline, respectively, and recoveries were close to 100%. Demonstration of the method by applying to the analysis of the concentrations of three methylxanthines in Mate beers as well as Mate beers and Mate soft drinks available from the market proved to be sensitive, accurate and reliable.

J. Chromatogr. A 1571, 223-230 (2018). Evaluation of lipophilicity of 11 representative drugs, including six proton pump inhibitors (omeprazole, pantoprazole, rabeprazole, lansoprazole, ilaprazole, and tenatoprazole), an anti-vertigo drug, betahistine, nonsteroidal anti-inflammatory drug, ibuprofen, anti-malarial drug, atovaquone, an anti-HIV agent, atazanavir and a hormonal drug, calcitriol, by employing NP and RP separation modes. Investigation of the effect of different organic modifiers for the estimation of lipophilicity. Estimation of the quantitative descriptor of lipophilicity, the partition coefficient (logP) by suitably optimizing the solvent systems for normal and reversed phase TLC. The best mobile phase pairs were toluene – acetonitrile and water – methanol, respectively. Analysis of the dominant pattern in the data by using principal component analysis, hierarchical cluster analysis, as well as non-parametric methods like sum of ranking differences and generalized pair wise correlation. The results obtained from both separation modes were comparable and in good agreement with the computational data for all the drugs.

J. Ethnopharmacol. 232, 135-144 (2019). HPTLC of hesperidin in Citrus reticulatae pericarpium on silica gel with ethyl acetate – formic acid – acetic acid – water 15:1:1:2. Qualitative identification at UV 275 nm. The hRF value for hesperidin was 26.