J. Planar Chromatogr. 33, 263-269 (2020). HPTLC of the interaction between methylene blue and purified glutathione-S-transferase (5 mmol/L methylene blue and enzyme solution in 0.1 mol/L potassium phosphate buffer) on silica gel with butanol - acetic acid - water 12:3:5 for 2 h. Detection by spraying with ninhydrin (0.25 % in acetone). The complex that most likely came from the interaction of methylene blue and purified glutathione-S-transferase had a hRf of 16.

J. Liq. Chromatogr. Relat. Technol. 43, 233-246 (2020). HPTLC of lutein (1) and lactucaxanthin (2) in three varieties of lettuce (Iceberg, Romania, and green lettuce) on silica gel with heptane - acetone 7:3. The hRF values for (1) and (2) were 44 and 41, respectively.

J. Liq. Chromatogr. Relat. Technol. 43, 445-454 (2020). HPTLC of aniline (1), 2,4-xylidine (2) and 4-aminoazobenzene (3) in chili oils, pickles and related food matrices on silica gel with chloroform - acetic acid 9:1. Quantitative determination by absorbance measurement at 280 nm. The hR_F values for (1) to (3) were 53, 43 and 82, respectively. Linearity was in the range of 2-14 ppm for (1) to (3). The LOD and LOQ were 0.0015 and 0.0045 ppm for (1), 400 and 1200 ppm for (2) and 200 and 600 ppm for (3), respectively. Mean recovery rate was 100.2 % for (1) and 100.9 % for (2). The azo aryl amines were also analyzed using a TLC-MS interface.

J. Planar Chromatogr. 33, 11-18 (2020). HPTLC of lutein in dietary supplements on silica gel with n-heptane – ethyl acetate 9:1. The part of the TLC chromatogram containing the zone visible in day light was cut off, followed by developing in the opposite direction with n-heptane – acetone – ethyl acetate 11:5:4. Quantitative determination by absorbance measurement at 450 nm. Linearity was between 90 and 500 ng/zone for lutein. Intermediate precisions were below 2 % (n=9). The LOD and LOQ were 50 and 90 ng/zone, respectively. Recovery rate was between 87 and 102 %.

J. Planar Chromatogr. 32, 59-60 (2019). TLC of p-phenylenediamine on silica gel with ethyl acetate - diethyl ether 1:1. Detection by spraying with aqueous alkaline solution of Folin’s reagent (0.5 % Folin’s reagent in 5 % sodium carbonate solution). The hRF value of p-phenylenediamine was 45. The LOD for p-phenylenediamine was approximately 3 μg by visual evaluation.

J. Chromatogr. 411, 437-444 (1987). Reversed-phase TLC on octadecyl-bonded silica with methanol - acetonitrile - 5% sodium sulfate 3:3: 10 and methanol - MEK - 5% sodium sulfate 1:1:1.

J. Food Hygienic Society of Japan (Shokuhin Eiseigaku Zasshi) 39, 286-291 (1998). TLC on RP-18 with 1) methylethylketone - methanol - 5% aqueous sodium sulfate solution 1:1:1, 2) acetonitrile - methanol - 5% aqueous sodium sulfate solution 1:1:1. Measurement of the visible absorption spectra by using sample concentration techniques, which improved the detection limits 10 - 20 fold. Use of the method for identification of coal tar dyes in 48 food samples.

Anal. Chem. 81, 4121-4129 (2009). The polymer used for electrospinning the new stationary phase was polyacrylonitrile with a molecular weight of ca.150.000 in dimethylformamide as solvent; the substrate for the fibers was aluminium foil. The new material showed fiber diameters that are 400 nm. The most efficient layer thickness was 25 µm. The eletrospun plate, which was a cut, rectangular plate roughly sized 3 × 6 cm, was compared to (1) TLC on silica gel with acetonitrile - methanol 3:2 for mixtures of laser dyes (sulforhodamine 640, pyrromethene 597, rhodamine 610 perchlorate, rhodamine 610 chloride, rhodamine 590 chloride, rhodamine 101, and kiton red), and (2) TLC on cyano phase with water - acetone 7:3 for steroidal compounds (androsterone, cholesterol, and cortisone), both with chamber saturation for 10 min. The development time was comparatively faster. Detection under UV light and by spraying with molybdenum phosphoric acid and heating at 120 °C for 10 min. Plate heights (Note: referred to the migration distance of the solvent front instead of substance zone) of max. 120.000 per meter resulted and were comparatively better. Two-dimensional TLC had a similar efficiency compared to one-dimensional separation (no major peak broadening was observed).