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.

Chem. (Bunseki Kagaku) 34, 612-618 (1985). (Japanese). (High-purity, high-recovery purification of prednisolone by the automatic recrystallization method and its purity evaluation by thin-layer chromatography and by differential scanning colorimetry.) TLC of prednisolone on silica with chloroform - methanol 9:1. Detection by UV 254 nm.

J. Chromatogr. 465, 448-450 (1989). Two-dimensional TLC of title compounds on silica with ethyl acetate - chloroform 2:1 for the 1st direction and benzene - chloroform - methanol - 5 M acetic acid 70:20:20:1 for the 2nd. Detection of the fluorescent spots under UV light.

J. Liq. Chromatogr. Relat. Technol. 29, 1891-1903 (2006). HPTLC of androsterone, epi-androsterone, dehydro-epi-androsterone, testosterone, stigmasterol, beta-sitosterol, estradiol, hydrocortisone, and cholesterol on RP-18 W with methanol - water, and acetonitrile - water in different composition, with chamber saturation. Detection by spraying with sulfuric acid - methanol 1:9 and heating at 120 °C for 15 min. Densitometric determination of RF values. The aim of the work was to compare the lipophilicity of selected steroids determined by RP-HPTLC on RP-18 W plates using different mobile phases with lipophilicity values estimated by computational methods.

J. Chromatogr. 350, 468-470 (1986). TLC of various steroids on silica with chloroform - methanol 10:1. Detection with 1 % solution of rubeanic acid in conc. sulfuric acid. Detection limit up to 100 ng for various types of steroids. Densitometric determination at 254 nm.

J. Planar Chromatogr. 3, 34-37 (1990). Investigation of the retention behavior of 12 steroids (cholesterol, allylestrenol, pregnanediol, progesterone, estradiol, estrone, estriol etc.) using PR-HPTLC systems with acetonitrile – methanol, acetonitrile – water, and methanol – water binary mixtures. The separation abilities of the mobile phases considered were studied using the principal component analysis method. Visualization by spraying with a mixture of 10 g copper sulfate and 5 mL o-phosphoric acid (86%) dissolved in 95 mL methanol.

J. Liq. Chromatogr. Relat. Technol. 29, 2035-2044 (2006). TLC of androsterone, epi-androsterone, dehydro-epi-androsterone, testosterone, stigmasterol, beta-sitosterol, estradiol, hydrocortisone, and cholesterol on silica gel with chloroform - acetone 17:3 and activation at 100 °C, 120 °C, 150 °C, and 200 °C during 15, 30, 60, and 120 min. Activation time temperature influenced Rf values and order of separated compunds.