J Chromatogr A, 1608, 460415 (2019). Samples were acetonitrile extracts of Annona cherimola fruit peel, pulp and seeds (Annonaceae), as well as caffeic acid as standards. HPTLC on silica gel with chloroform – ethyl acetate – propanol 21:2:2 for peel extracts, with chloroform – methanol 9:1 for seed extracts. Derivatization by spraying Dragendorff’s reagent for alkaloids, secondary amines and non-nitrogenous oxygenated compounds.  Effect-directed assay was performed for inhibitors of α-glucosidase. Before sample application, plates were developed with enzyme substrate (2-naphthyl-α-D-glucopyranoside 0.1 % in methanol) and dried 20 min at 60 °C. Then, samples were applied and separated, and mobile phase was removed by heating 10 min at 60 °C. The chromatogram was sprayed with 4 mL enzyme solution (5 unit/mL in 100 mM phosphate buffer,  pH 7.4), liquid excess was removed under lukewarm air stream, the plate was incubated 10 min at 37 °C in a moisture box, followed by spraying chromogenic reagent Fast Blue salt B 0.1 % in water, giving after 2 min white inhibition bands visible on purple background under white light. Plate image was documented under illumination (reflectance mode) with white light. The bands of 3 inhibiting compounds were analyzed in a triple quadrupole mass spectrometer. 1) Full scan mass spectra (m/z 50−1000) in the positive ionization mode were recorded using electrospray ionization (ESI, spray voltage 3 kV, desolvation line temperature 250 °C, block temperature 400 °C) for compounds directly eluted with methanol – acetonitrile through the oval elution head of a TLC-MS interface pump. 2) Compounds were also isolated (either eluted directly from the plate into a vial through the same interface, or scraped from the plate and extracted with methanol – chloroform into a vial), dried, and submitted to HPLC-DAD-MS/MS; MS-MS spectra were recorded in the same conditions, using argon as collision gas and collision cell voltages from -20 and -40 V. Inhibitors were identified as phenolamides (phenylethyl cinnamides): moupinamide (hRF 66 in peels, 56 in seeds), N-trans-feruloyl phenethylamine (hRF 76 in peels), N-trans-p-coumaroyl tyramine (hRF 44 in seeds).

J. Planar Chromatogr. 35, 61-71 (2022). HPTLC of empagliflozin (1) in the presence of metformin HCl (2) on silica gel with toluene - methanol - ammonia - glacial acetic acid 72:26:1:1. Quantitative determination by absorbance measurement at 230 nm. The hRF values for (1) and (2) were 15 and 48, respectively. Linearity was between 11 and 112 ng/zone for (1) and 85 and 850 ng/zone for (2). Interday and intra-day precisions were below 2 % (n=3). The LOD and LOQ were 0.6 and 1,7 ng/zone for (1) and 5 and 15 ng/zone for (2), respectively. Recovery was found to be in the range of 99.4-101.0 % for (1) and 100.3-101.4 % for (2). Degradation products were characterized by liquid chromatography coupled with electrospray ionization‒quadrupole-time of flight‒tandem mass spectrometry (LC‒ESI‒QTOF‒MS/MS).

Rapid Commun. Mass Spectrom. 34, 8755 (2020). HPTLC of a synthetic formulated gasoline (diluting polypropylene glycol and polyisobutylene succinimide polyamine surfactant at a mass ratio of 1 % in gasoline) on silica gel with methanol - toluene 2:3. Detection under UV light. Samples were scratched for analysis by atmospheric solids analysis probe mass spectrometry (ASAP-MS).

J. Sep. Sci. 43, 2981-2988 (2020). HPTLC of citicoline (1) and piracetam (2) in presence of their degradation products on silica gel with methanol - chloroform - ammonium chloride buffer 9:1:2. Quantitative determination by absorbance measurement at 230 nm. The hRF values for (1) and (2) were 15 and 85, respectively. Linearity was between 0.2 and 4 µg/zone for both (1) and (2). Intermediate precision was below 2 % (n=3). The LOD and LOQ were 56 and 180 ng/zone for (1) and 53 and 170 ng/zone for (2), respectively. Average recovery was 100.9 % for (1) and 99.8 % for (2).

J. Planar Chromatogr. 33, 219-229 (2020). HPTLC of carbamazepine (1) and its degradation product iminostilbene (2) on silica gel with petroleum ether - acetone 7:3. Quantitative determination by absorbance measurement at 230 nm. The hRF values for (1) and (2) were 12 and 63, respectively. Linearity was between 0.1 and 1.4 µg/zone for (1) and 0.1 and 1.2 µg/zone for (2). Intermediate precision was below 2 % (n=3). The LOD and LOQ were 0.03 and 0.09 µg/zone for (1) and 0.03 and 0.09 µg/zone for (2), respectively. Average recovery was  99.7 % for (1) and 99.7 % for (2).

J. Ethnopharmacol. 235, 361-374 (2019). HPTLC of colchicine (1) and withaferin A (2) in the polyherbal ayurvedic formulation Peedantak Vati (PV) on silica gel with chloroform - 
methanol - water - formic acid 140:13:2:4. Quantitative determination by absorbance measurement at 218 nm. The hRF values for (1) and (2) were 22 and 28, respectively. LOD and LOQ were 40 and 120 ng/zone for (1) and 120 and 240 ng/zone for (2), respectively.  

Asian J. Chem. 20(4), 2531-2538 (2008). TLC of melatonin on silica gel with toluene - ethyl acetate - formic acid 10:9:1. Quantitative determination by absorbance measurement at 290 nm. The method was linear in the concentration range of 100 to 600 ng/spot. The recovery of the drug from tablets (by standard addition method) was 99.7 %. Statistical analysis proves that the method is repeatable, selective and accurate for the estimation of the drug. Forced degradation studies showed the effect of variations in pH, UV light and high temperature on the stability of melatonin. As the proposed method could effectively separate the drug from its degradation products, it can be employed as a stability indicating method.

62nd Indian Pharmaceutical Congress Abstract No. F-235 (2010). TLC of metformin and glimepiride on silica gel with 0.5 % ammonium sulfate – water – methanol – ethyl acetate 2:2:1:1. Quantitative determination by absorbance measurement at 254 nm. The method was found to be linear in the range of 300-500 ng/band for glimepiride and 150-250 µg/band for metformin.