Heliyon 7(2), e06116 (2021). Samples were a methanolic extract of a semi-solid ayurvedic conserve (ashwagandhadi lehyam) prepared with Withania somnifera roots (Solanaceae) and five other plants, as well as standards: withaferin A and withanolide A (= withaniol), two ergostane triterpene steroids with lactone cycle and epoxide. HPTLC on silica gel with toluene – ethyl acetate – formic acid 6:4:1. Visualization and densitometric scanning at UV 254 nm and 366 nm (deuterium lamps). Derivatization by immersion into vanillin – sulfuric acid reagent, followed by oven heating at 105 °C until optimal coloration. Documentation under white light and densitometry scanning at 540 nm (tungsten lamp). Both analytes (hRF 35 and 45 respectively) were shown at 254 nm and 540 nm (but not at 366 nm), in the standards and in the extract.

J Chromatogr A, 1669, 462942 (2022). Samples were medroxyprogesterone acetate (MPA) as standards and commercial drug extracts, dissolved in dichloromethane. TLC on silica gel (preactivated by 30 min heating at 120 °C) with dichloromethane – ethyl acetate 10:1, followed by 30 min drying at 120 °C. Derivatization by spraying with sulfuric acid (50 % in ethanol). Visualization in a 3D-printed chamber designed especially for this purpose, blocking extraneous light and including a smartphone holder, a fluorescent lamp and an optical density step tablet. Pictures were taken with the smartphone digital camera, after spraying (6 background images) and after 10 min heating at 120 °C (6 foreground images). In the last case, MPA appeared as black spots (hRF 16–20). Using an image processing software program: (1) one averaged background image and one averaged foreground image were created by concatenation and were split into 3 colour channels; (2) the green colour channels were corrected to remove background noise, by subtraction of an averaged darkfield image (taken on blank plate without light) and by comparison ratio to an averaged blankfield image (taken on blank plate with light); (3) the pixel values of the MPA bands were converted to optical density values through the Robard’s function, by comparison to a reference image of a theoretical optical density step tablet; (4)  furthermore, the corrected background image was subtracted from the corrected (and denoised with a Gaussian Blur) foreground image; a triangle threshold algorithm was applied on the resulting image, and was converted to a mask (white spots on black background); (5) applying the binary mask to the original corrected images (obtained in (2)), the final integrated density values of MPA spots were obtained. This method was validated for linearity range (1.25–3.75 mg/mL), for precision, for reproducibility, for robustness, and for accuracy expressed as average recovery values (101 % overall mean) by comparison of TLC results with HPLC-DAD results.

J Chromatogr A 1638, 461895 (2021). Samples were sphingolipid-rich fractions of unproteinated blood plasma from healthy humans or from Fabry’s disease patients, as well as standards of sphingomyelin (SM) and of globotriaosylceramides (Gb3 = ceramide trihexosides), and related compounds (lyso-ceramide trihexosides, lactosyl ceramide, glucosyl ceramide). HPTLC on silica gel (Lichrosphere with spherical particles) by automated multiple development with a 9-step gradient, starting with pure methanol and ending with dichloromethane – methanol 9:1. Visualization and densitometry under UV 190 nm. Derivatization for Gb3 and derivatives (but not for SM) by immersion into orcinol solution (0.2 %, with sulfuric acid 10 %), followed by 15 min heating at 100 °C and by densitometry under visible light 550 nm. Bands of interest were directly eluted with methanol from underivatized plates into an ion-trap MS, through the oval head of a TLC-MS interface (with stainless steel frit to remove silica gel particles). Two different ionization processes were used: (A) electrospray ionization (ESI, capillary voltage 4 kV, endplate offset voltage -0.5 kV, nebulizer pressure 40 psi, drying gas 9 mL/min at 350 °C); (B) atmospheric pressure chemical ionization (APCI, capillary voltage 2–3 kV, current intensity 4.5 µA, nebulizer pressure 45 psi, drying gas 5 mL/min at 350 °C; vaporization at 450 °C). Full MS spectra were recorded up to m/z 1500 in positive ion mode. The relative ion intensities were used to quantify the detected species. Previous to this study, the precision of the elution head positioning was tested on Gb3 standard zones, comparing 3 positions for analyte elution: from the centre and from each higher or lower side of the band. The same main m/z peaks were observed in the 3 positions, but in different proportions. This was explained by the presence of coeluting Gb3 subclasses (the ceramide moiety CM being either saturated, mono-unsaturated fatty acyl with a slightly higher migration distance, or polar hydroxyl fatty acyl with the opposite effect on migration) and of coeluting Gb3 isoforms (the hexoside moiety consisting of glucose and/or galactose units). This resulted in the broadening and partial splitting of the standard band. In the plasma samples, 19 molecular species of Gb3 were identified (depending on the CM, the sugar isoforms being undistinguishable by MS): 5 with a saturated CM, 7 with two additional double bonds on the CM, 7 with a methylated CM. In case of Fabry’s disease, most Gb3 species with saturated CM were highly increased, whereas other species were decreased.

Heliyon 8(8), e10103 (2022). Samples were a methanolic extract of Cymbopogon giganteus leaves (= C. caesius subsp. giganteus, Poaceae), as well as flavones as standards: isorhamnetin, luteolin and orientin (=luteolin 8-C-glucoside). HPTLC on silica gel with ethyl acetate – acetic acid – formic acid – water 100:11:11:26. Derivatization for flavones with Neu’s reagent (ethanolamine diphenylborate – PEG). Visualization under UV 365 nm. The standards (hRF 75, 70-72 and 96, respectively) were not detected in the extract. Some analytes detected by the reagent were scraped from the underivatized plate into a tube, and injected through a TLC-MS interface into a double-quadrupole – time-of-flight MS (electrospray ionization). Full mass scan spectra were recorded in positive and negative ionization modes in m/z range 150–550. For 3 of the compounds, isolated through MPLC columns, the HPTLC-MS results, combined to the NMR and HPLC-MS analyses, allowed the identification as epicatechin (hRF 86, a flavanol, not coloured by Neu’s reagent) and as luteolin 8-C- and 6-C-glucosides (hRF 67-70).

Plant Med 88(2), 163-178 (2022). TLC was used to verify the purity of acetoxychavicol acetate (a phenylpropanoid) isolated through column chromatography from a hexane extract of Alpinia galanga rhizomes (Zingiberaceae). TLC on silica gel with n-hexane – ethyl acetate 17:3, evaluation under UV 254 nm.

Front. Pharmacol. 13, 925298 (2022). HPTLC of milk thistle on silica gel with toluene - ethyl formate - formic acid 8:10:1. Detection by dipping in NP reagent and subsequently in PEG reagent, followed by heating at 100 °C for 5 min. Qualitative analysis under UV light at 254 and 366 nm. HPTLC of alkylamides in coneflower on silica gel with ethyl acetate - ethyl methyl ketone - water - formic acid 5:3:1. Detection by dipping in NP reagent and subsequently in PEG reagent, followed by heating at 100 °C for 5 min. Qualitative analysis under UV light at 254 and 366 nm. HPTLC of black cohosh on silica gel with toluene - ethyl formate - formic acid 5:3:2. Detection by dipping into sulfuric acid reagent (20 mL of sulfuric acid in 180 mL of methanol), followed by heating at 100 °C for 5 min. 

J. Sep. Sci. 45, 1305-1316 (2022). HPTLC of tamsulosin hydrochloride (1) and solifenacin succinate (2) along with their impurities on silica gel with ethyl acetate - butanol - glacial acetic acid 100:4:1. Quantitative determination by absorbance measurement at 225 nm. The hRF values for (1) and (2) were 61 and 26, respectively. Linearity was between 0.1 and 1.0 µg/zone for (1) and 1.0 and 15.0 µg/zone for (2). Inter-day and intra-day precisions were below 2 % (n=6). Mean recovery was 99.9 % for (1) and 99.8 % for (2). 

J. Sep. Sci. 45, 4187-4197 (2022). HPTLC of tadalafil (1) and canagliflozin (2) in spiked and real human plasma on silica gel with ethyl acetate - toluene - methanol 2:2:1. Quantitative determination by absorbance measurement at 291 nm. The hRF values for (1) and (2) were 73 and 55, respectively. Linearity was between 0.5 and 25 ng/zone for both (1) and (2). Inter-day and intra-day precisions were below 2 % (n=6). The LOD and LOQ were 0.14 and 0.43 ng/zone for (1) and 0.16 and 0.47 ng/zone for (2). Recovery was between 96.1 and 100.7 % for (1) and 97.6 and 102.0 % for (2).