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.

Food Chem. 133610 (2022). HPTLC of hormonal active compounds in 68 different botanicals on silica gel with ethyl acetate - toluene - formic acid - water 16:4:3:2. The plate was neutralized by spraying with citrate phosphate buffer (6 g/L citric acid monohydrate and 10 g/L disodium hydrogen phosphate in double-distilled water, adjusted to pH 12 by solid sodium hydroxide). To overcome diffusion caused by long bioassay incubation, zone fixation was achieved by coating with polyisobutyl methacrylate (0.25 % Degalan in n-hexane), followed by drying. The prepared yeast cell culture was piezoelectrically sprayed onto the plates, followed by incubation at 30 °C for 4 h. The substrate solution (2 mg 4-methyl umbelliferyl-β-D-galactopyranoside in 100 μL dimethyl sulfoxide and 3 mL citrate buffer) was piezoelectrically sprayed, followed by incubation at 37 °C for 1 h, dried, and documented by fluorescence light detection at 366 nm. The resulting NP-HPTLC–UV/Vis/FLD–pYAVAS–FLD bioassay allowed the detection of androgens, antiandrogens, false-positive antiandrogens, and synergists in complex mixtures.

J. Planar Chromatogr. 26, 56-61 (2013). TLC of ofloxacin (1) and dexamethasone (2) on silica gel with methanol - 0.01 M phosphate buffer 2:3 and pH adjusted to 5 with orthophosphoric acid. Quantitative determination by absorbance measurement at 300 nm for (1) and 240 nm for (2). The hRf values for (1) and (2) were 22 and 60, respectively. Linearity was in the range of 1-6 µg/zone for both (1) and (2). The LOD and LOQ were 260 and 870 ng/zone for (1) and 220 and 740 ng/zone for (2), respectively. Average recovery (by standard addition) for (1) and (2) was 99.2 %. Intermediate/interday/intra-day precision was below 2 % (n=3). The method showed comparable results with a validated HPLC method.

(Hungarian). Magyar Kémiai Folyóirat 95, 33-37 (1989). TLC of 4-androsten-3,17- dione and testosterone on silica with ethyl ether - toluene 2:1. Visualization with ethanol - phosphoric acid 1:1 reagent.

J. Planar Chromatogr. 11, 305-308 (1998). Investigation of the chromatographic behavior of dexamethasone, prednisolone, and other representative corticosteroids. - 12 Different mixtures of organic solvents were compared to assess their efficiency as mobile phases for the separation of 18 glucocorticosteroids by TLC. Optical evaluation of the plates after treatment with 4 different spray reagents then revealed that the combination of choice for optimum separation and detection was chloroform- methanol 23:2, or chloroform - acetone 9:1 and a mixture of 2,4-dihydroxybenzaldehyde, sulfuric acid, and acetic acid as spray reagent. The specificity of these chromatographic conditions was assessed by analysis of 35 anabolic steroids and 10 other veterinary drugs. No significant interferences were found.

J. Chromatogr. 295, 308-311 (1984). TLC separation of steroids which differ by only one double bond on silver nitrate impregnated silica with benzene - ethanol 9:1, benzene - ethyl acetate 2:1, ether - benzene 2:1, hexane - ethyl acetate 1:1 and other solvent systems. Detection with ethanol - sulfuric acid 1:1. Also TLC of steroids after bromination on the plate.

Acta Pharmaceutica Hungarica 59, 167-172 (1989). TLC of 2ß,16ß-bis-(4'-dimethyl-1‘piperazino)-3a,17ß-diacetoxy-5a-andro stane (=Arduan) on silica with chloroform - dichloromethane - methanol 6:2:2. NaI in an unsaturated development tank sealed airtight. Determination of radioactivity of the parent drug and metabolites separated by ion-pair TLC.

Dtsch. Apoth. Ztg. 139, 517-518 (1999). Approved procedure for identity and quality test TLC and HPTLC of betamethasone 17a-valerate (using prednisolone acetate, hydroxycortisone acetate or dexamethasone acetate as reference substances) on silica gel with ethyl methyl ketone - toluene 2:3; without chamber saturation, bandwise application. The plate is left in the air for 15 min after application. Detection under UV 254 nm, after spraying with ethanolic sulfuric acid solution and heating at 110°C, and under UV 360 nm.