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.

J. Planar Chromatogr. 26, 202-208 (2013). HPTLC of egg yolk lipid fractions on silica gel with hexane - diethyl ether - formic acid 40:10:1. Detection by srpaying with 10 % copper(II) sulfate in 8 % phosphoric acid. Quantitation by scanning with a flatbed scanner and a gel analysis software. Intermediate/interday/intra-day precision was below 10 % CV (n=6).

Anal. Chem 55, 1858-1862 (1983). Description of a single beam imaging spectrophotometer capable of recording the reflectance or transmittance spectra of up to 64000 positions on an object within a few minutes. The transmission image is recorded by a SIT vidicon interface to a digital computer. Data can be presented as a three-dimensional array and stored on disc for later postrun processing; quantitatively and qualitatively. Preliminary results show that the method should be suitable for quantifying submicrogram fractions on TLC plates, even when chromatographic resolution is incomplete.

H. TRAITLER, A. STUDER, R.E. KAISER (eds): Instrumental HPTLC, Institute for Chromatography, Bad Dürkheim, FRG (1987), 321-329. Description of the hardware and software for quantitative evaluation of TLC with image processing scanner taking the quantitative evaluation of (-)-a-bisabolol in essential oil as example. Detection limit 200 ng. Standard deviation of measurements 3%.

J. Chromatogr. 463, 139-145 (1989). Description of a new quantification method, laser pyrolysis, for TLC without the need of visualization process in detecting any organic compound. Use of 2 amino acids, 2 pesticides as test samples. Complete analysis time less than 20 min. Comparison of sensitivity and linearity with densitometry. This technique combines the advantage of the separation power of TLC and GC detection methods. Detection limits, 100 ng for phenylalanine with FID and 20 ng for methoxychlor with ECD.

J. Planar Chromatogr. 2, 198-202 (1989). A new detector (Digital Autoradiograph, DAR) has been developed which measures, quantitatively position and intensity of 2-dimensional distributions of ionizing radiation from radioisotope labelled TLC plates. Examples and results of typical applications are presented, e.g. metabolites of pesticides or chloramphenicol-acetyl-transferase assay.

J. Planar Chromatogr. 6, 487-491 (1993). Study on the possibilities of using liquid crystals to perform quantitative determinations of organic compounds separated by TLC. Quantitative analysis reduces to simple measurements of the temperature at which the spot of the substance to be determined appears as mapped on a liquid crystalline detector.