J. Ethnopharmacol. 202, 97-102 (2017). HPTLC of betaine in the roots of Achyranthes aspera on silica gel with methanol – water 9:1. Detection by spraying with Dragendorff's reagent, followed by 10 % ethanolic sulfuric acid and drying at 110 °C for 5 min. Quantitative determination by densitometry at 520 nm. The hRF value for betaine was 36. Linearity was between 1 and 5 μg/band. The intermediate precision was below 2 % (n=6). LOD and LOQ were 0.13 μg/mL and 0.10 μg/mL, respectively. (Note: The reported LOD and LOQ do not make sense, as LOD is higher than LOQ.)

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 1526, 137-150 (2017). HPTLC of physalins from crude extracts of Chinese lantern (Physalis alkekengi L.) on silica gel with ethyl acetate – toluene – formic acid 35:15:1. Densitometric screening of physalins in absorption and in fluorescence mode after post-chromatographic derivatization with sulfuric acid reagent. Identification of the physalin L standard and its impurity, 2,3,25,27-tetrahydrophysalin A. Applying two successive plate pre-developments with methanol – formic acid 9:1 and methanol to avoid strong ion suppression caused by the developing solvent additive (formic acid), and to improve the sensitivity of HPTLC-MS/MS method combined with a slightly modified developing solvent ethyl acetate – toluene – formic acid 30:20:1. Non-targeted characterization of physalins from the same chromatographic zone and determination of physalin types by simultaneous hyphenation of HPTLC with a triple quadrupole and an ion trap mass analyzer. Demonstration of the performance of the HPTLC-densitometric and HPTLC–MS/MS methods for the analysis of physalins from aqueous reflux extracts. Observation of variations in physalin profiles and abundances in different parts of P. alkekengi harvested at different stages of maturity, showed that the husks are the most suitable plant part for P. alkekengi quality control.

CBS 117, 5-7 (2016). HPTLC of amylase-produced dextrins and standards glucose, maltose, maltotriose, maltotetrose, maltopentose, maltohexose, and maltoheptose on silica gel with acetonitrile – acetone – water 3:3:2 with chamber saturation to a migration distance of 60 mm. Detection by immersion into aniline-diphenylamine-phosphoric acid reagent (2 g diphenylamine and 2 mL aniline in 80 mL methanol in 10 mL 85 % phosphoric acid, made up to 100 mL with methanol) followed by heating at 120 °C for 5 min. Evaluation under white light. Quantitative determination by absorbance measurement at 500 nm. Evaluation in the polynomial working range of 40-210 ng/band.

J. Planar Chromatogr. 31, 7-12 (2018). HPTLC of L-histidine (1), L-glycine (2), L-alanine (3) an L-phenylalanine (4) in Steatoda grossa spider web on silica gel with 2-butanol – acetone – glacial acetic acid – water 7:7:2:4. Detection by spraying with 0.5 % solution of ninhydrin in methanol, followed by heating at 100–110 °C for 10 min. Quantitative determination by absorbance measurement at 500 nm. The hRF values for (1) to (4) were 11, 35, 48 and 72, respectively. Linearity was between 0.2 and 1.0 μg/zone for (1) and (2), 0.1 and 0.5 μg/zone for (3) and 0.3 and 1.5 μg/zone for (4). LOD and LOQ were 185 and 556 ng/zone for (1), 154 and 461 ng/zone for (2), 100 and 302 ng/zone for (3) and 152 and 456 ng/zone for (4).

J. Planar Chromatogr. 31, 155-162 (2018). HPTLC of lawsone in Lawsonia inermis on silica gel with benzene ‒ ethyl acetate ‒ acetic acid 75:25:1. Quantitative determination by absorbance measurement at 275 nm. The hRf value for lawsone was 33. Linearity was in the range of 50-350 ng/zone. The intermediate precision was below 2 % (n=6). The LOD and LOQ were 16 and 50 ng/zone for lawsone, respectively. Average recovery was 96 %.

J. Chromatogr. Sci. 55 (9), 954-960 (2017). Presentation of a simple, cost-effective and rapid stability-indicating assay for densitometric quantification of methyltestosterone, a synthetic testosterone derivative commonly used for the treatment of testosterone deficiency in males, in pharmaceutical formulation. TLC of methyltestosterone on silica gel with hexane – acetone 13:7. Quantitative determination by densitometry at 254 nm in absorbance mode. Evaluation via peak areas using linear regression. The LOD and LOQ were 2 and 6 ng/zone, respectively. Investigation of the degradation of methyltestosterone by applying various stress conditions such as hydrolysis under acidic, basic and neutral conditions, heating in anhydrous conditions and exposure to light. Good separation of the degraded products caused by photodegradation, acidic and basic hydrolysis, and identification of acid degraded product as 17,17-dimethyl-18-norandrosta-4,13(14)-dien-3-one by spectroscopy. Explanation of the reactivity of methyltestosterone under applied stress conditions by quantum chemical calculations. The developed method proved to be repeatable, selective and accurate for quantification of methyltestosterone and can be employed for routine analysis.

J. Liq. Chromatogr. Relat. Technol. 31, 203-222 (2018). HPTLC of fluorometholone (1) and sodium cromoglycate (2) on silica gel with ethyl acetate – methanol 9:1. Quantitative determination by absorbance measurement at 240 nm. The hRf values for (1) and (2) were 65 and 12, respectively. Linearity was in the range of 0.1-24.0 μg/zone for (1) and 0.2-48.0 μg/zone for (2). The intermediate precision was below 1.1 % (n=9). The LOD and LOQ were 9 and 270 ng for (1) and 170 and 510 ng for (2), respectively. Average recoveries for (1) and (2) were 100.3 and 100.7 %, respectively.