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. Planar Chromatogr. 32, 197-203 (2019). HPTLC of equol (1), artemisinin (2) and caffeine (3) on silica gel with methyl t-butyl ether - cyclohexane 1:1 for (1), cyclohexane - ethyl acetate 7:3 for (2) and ethyl acetate - acetone 7:3 for (3). The plate was scanned with a DART–TOF MS system to optimize the measurement conditions. The hRF values for (1) to (3) were 71, 63 and 53, respectively. LOD and LOQ were 1.2 and 1.8 µg/zone for (1), 225 and 315 ng/zone for (2) and 270 and 490 ng/zone for (3), respectivley.

Chromatographia 70 (1-2), 305-308 (2009). Description of color channel selection, three-dimensional visualization, and acquisition time of computerized image analysis for one-dimensional planar separation, known as computerized image analysis or video densitometry. This is an efficient, low-cost technique for quantitative and qualitative analysis of planar separations, e.g. planar chromatography and gel electrophoresis. The image of the TLC plate is captured in black and white, then the proper color channel of the image is selected in order to enhance the signal-to-noise ratio. To facilitate image evaluation a three-dimensional visualization of the planar image was applied by use of OpenGL technology. It was found that the sensitivity is increased by use of longer acquisition times whereas linearity of quantitative analysis is reduced.

Food Control 90, 48-57 (2018). HPTLC of saffron and its main adulterants (sumac, turmeric, safflower, common madder, quinoline yellow, sunset yellow and tartrazine) on silica gel with 1-butanol – acetic acid – water 4:1:1. Images were captured under visible light and subjected to MATLAB software. The method included image preprocessing capable of identifying such adulteration based on modelling that includes principal component analysis, k-means and chemometric methods such as partial least squares discrimination analysis, variable selection (loading weight and variable importance in projection) and linear discriminant analysis.

Anal. Biochem. 152, 391-395 (1986). Description of a method for quantification of 3H and 14C on thin layers after two-dimensional TLC. After impregnation with 50 % 2,5-diphenyloxazole-tetrahydrofuran, quantitative imaging of the distribution of b-ray-emitting isotopes on the chromatogram was carried out at room temperature using a TV camera system. The system consists of a 2-stage microchannel plate image intensifier, a low-lag vidicon, and an image processor.

J. Chromatogr. 437, 411-421 (1988). Description of a two-dimensional image-processing procedure for TLC ojects. Use of a computer-controlled high-speed scanning photometer in vertical remission mode. Presentation of the software for digital evaluation of chromatograms. Demonstration of the flexibility of the method with some typical examples. Detection limit, in ng range. Mean error < 2%.

Anal.Chem. 61, 1931-1933 (1989). Description of a laser-based indirect fluorometric detection method for TLC with two-dimensional scanning capability and without derivatization. Detection limit 6 ng. The linearity in indirect fluorometric detection is found to be over 2 orders of magnitude.

J. Planar Chromatogr. 5, 9-15 (1992). TLC of amiloride and an organic sulfonium salt (C13H17OS·AsF6) on silica C-8 resp. silica. Subsequent successful imaging of these samples directly from the TLC plates with high spatial resolution, high mass resolution, and high sensitivity.