J. Planar Chromatogr. 35, 473-479 (2022). HPTLC of capsaicin and dihydrocapsaicin as capsaicinoids in Habanero pepper pods on silica gel with cyclohexane - chloroform - acetic acid 7:2:1. Quantitative determination by absorbance measurement at 254 nm. The hRF value for capsaicinoids was 29. Linearity was between 0.5 and 4.0 µg/zone. Interday and intra-day precisions were below 6 % (n=6). The LOD and LOQ were 251 and 750 ng/zone, respectively. 

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).

J. Planar Chromatogr. 34, 549-557 (2021). HPTLC of brexpiprazole (1) and sertraline HCl (2) on silica gel with n-propanol - hexane - toluene - triethylamine 70:20:10:1. Quantitative determination by absorbance measurement at 254 nm. The hRF values for (1) and (2) were 36 and 47, respectively. Linearity was between 4500 and 15000 ng/zone for (1) and 90 and 300 ng/zone for (2). Interday and intra-day precisions were below 4 % (n=3). The LOD and LOQ were 163 and 495 ng/zone for (1) and 35 and 107 ng/zone for (2), respectively. Recovery was between 99.5 and 101.1 % for (1) and 99.4 and 102.0 % for (2).

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).

Food Control. 122, 107816 (2021). HPTLC of histamine in fish samples on a silica gel read-out strip coated with a ninhydrin@TiO2 complex (0.1 M titanium butoxide and 5 % ninhydrin as precursors) as self-visualization nanomaterial in the histamine target zone (hRF value of 24). Samples were developed using n-butanol - acetone - ammonia 20:5:2. Detection after heating at 80 °C for 30 s. Linearity was between 15 and 320 mg/kg. The LOD for histamine was 5 mg/kg. 

Chem. Asian J. 15(19), 3044-3049 (2020). The studied rotaxane combines a dibenzocrown of 8 ethers (DB24C8) with an axle chain (Ax) containing two amines, one of them in an aniline group, allowing stability of the rotaxane even when the other one is unprotonated. TLC on silica gel in 4 steps, with detection under UV light or after derivatization with phosphomolybdic acid in ethanol. (1) Before the synthesis of the rotaxane, unprotonated Ax was isolated by preparative TLC of the protonated Ax obtained by addition of HCl or toluenesulfonic acid (TsOH); the mobile phases were chloroform – methanol 10:1 and toluene – tetrahydrofurane 3:2, respectively. The isolated molecules were confirmed as totally unprotonated Ax by NMR, suggesting a complete loss of HCl and TsOH on the silica gel layer. (2) After synthesis, unprotonated rotaxane, pure vs. monoprotonated by the addition of 10 different acids (and purified by column chromatography CC), was applied on TLC plates and developed with dichloromethane – acetone – water 3:16:1; the hRF values were very different, depending on the counter-anions from the used acids. (3) The same behavior (except with sulfuric acid) was observed under the same conditions when CC was omitted (unprotonated rotaxane samples were mixed with each of the acids, or with two acids at the same time for acid-competitive TLC analysis). (4) When unprotonated rotaxane was applied under the same conditions as in step (3) with the sodium salts instead of the acids, the behavior was similar (except for the shapes of the spots, due to the salts in excess). The rotaxane can thus be used for the TLC separation and detection of sodium salts, by forming salts of protonated rotaxane with the anion afforded by these sodium salts. The rotaxane protonation seems to be promoted by the methanol of the spotting mixture; indeed, when step (3) was performed with the mobile phase chloroform – methanol 10:1, a second zone appeared because methanol formed a salt with the rotaxane (identified by NMR).

J. Planar Chromatogr. 33, 669-677 (2020). HPTLC of tris(2-chloroethyl)amine (HN-3) on silica gel with benzene - methanol - triethylamine 425:75:1. Detection by spraying with derivatization reagent (2mg/mL of KMnO4 with 4 mL of H3PO4). The method allowed to study the influence of pH on the degradation of HN-3 and the triethanolamine rate of appearance.