J. Planar Chromatogr. 29, 45-58 (2016). Vertical chamber dielectrochromatography (V-LDEC) of two lipophilic dyes, Sudan blue (1) and Sudan II (2) on plates containing increasing amounts (1, 2, 3, 4, 6, 8, 10) g of barium titanate in 35 g alumina with toluene – n-hexane 1:1. The periods of maintaining the electric field consisted of 3 cycles, one cycle of about 17 min. The voltage between the armatures for each experiment was maintained at 3 kV AC value. Improved separations were obtained for the ratios of 2:35 and 3:35 (g/g) barium titanate – alumina both in equicurrent and mostly in countercurrent.

J. AOAC Int. 101, 1397-1401 (2018). HPTLC of sudan red dyes, namely Sudan orange G (1), Sudan red G (2), Sudan I (3), Sudan II (4), Sudan III (5) and Sudan IV (6) in spices and spice mixtures on RP-18 acetonitrile – methanol – aqueous ammonia solution (25 %) 40:9:1. Quantitative determination using a flatbed scanner with a 16-bit resolution. The hRF values for (1) to (6) were 54, 48, 57, 35, 26 and 17, respectively. Linearity was between 20 and 500 ng/zone for (1) to (6). LOD and LOQ were 17 and 35 ng/zone for (1), 11 and 21 ng/zone for (2), 14 and 31 ng/zone for (3), 12 and 24 ng/zone for (4), 18 and 42 ng/zone for (5) and 16 and 37 ng/zone for (6), respectively.

A simple chromatographic system for the identification of inks. J. Chromatogr. 475, 451-456 (1989). Proposal of a simple TLC system for the identification of inks based on cellulose layer, solution of ammonium sulfate or 1% sodium chloride as developing solvent; UV detection and photo dokumentation.

Chinese J. Environ. Chem. (Huanjing Huaxue) 12, 225-230 (1993). TLC of 7 dyes on silica with 14 different solvent systems (two for each dye). Identification by comparison colors and Rf values with those of standards. Confirmation and quantification by HPLC.

Chem. Environ. Res. 6, 49-55 (1997). OPLC of quinoline yellow (E104), sunset yellow (E110), cochineal red A (E124), indigo carmine (E132), tartrazine (E102), amaranth (E123), erythrozine (E127) on silica gel with NH3 - methanol - ethyl acetate 1:3:6 and NH3 - MEK - n-butanol 2:3:5 to 80 mm. Limits of detection are below 0,5 µg. E127 migrates in both solvent systems into the demixing zone. Thus, it could not be determined quantitatively. Significantly decrease in time of chromatographic analysis as compared to conventional TLC.

J. Planar Chromatogr. 23, 23-27 (2010). HPTLC of ziprasidone (5-[2-[4-(1,2-benzothiazol-3-yl)piperazin-1-yl]ethyl]-6-chloro-1,3-dihydroindol-2-one) on silica gel with hexane - dioxane - propylamine 5:45:2 up to 9 cm (under saturated conditions) and on RP8 with tetrahydrofuran - phosphate buffer (pH 9.0) 1:1 up to 4.5 cm (under unsaturated conditions), both in horizontal chambers. Quantitative determination by videodensitometry at 254 nm. Calibration was linear in the range 0.2-1.2 and 0.1-1.1 µg/spot ziprasidone for NP-HPTLC and RP-HPTLC, respectively. The intra-day precisions for 0.4-1.2 µg/spot on NP-HPTLC was 2.0 to 5.2 % and on RP-HPTLC 4.0 to 6.1 %; the respective inter-day precision for NP-HPTLC was 2.0 to 6.7 % and for RP-HPTLC 4.1 to 7.1 %. LOD/LOQ on NP-HPTLC was 0.03/0.09 µg/spot; using RP-HPTLC, LOD/LOQ was 0.02/0.06 µg/spot. The specificity of the methods was confirmed by comparison of hRf values (74 +/- 2 in NP-HPTLC and 36 +/- 1 in RP-HPTLC, n=12).

J. Braz. Chem. Soc. 27, 1067-1077 (2016). HPTLC for the kinetic study involving the conversion of 2,3-dichloro-6,7-dinitroquinoxaline (1) into 2-chloro-6,7-dinitro-3-pyrrolidinoquinoxaline (2) and then into 6,7-dinitro-2,3-dipyrrolidinoquinoxaline (3) on silica gel through monosubstitution of a chlorine group with one equivalent of pyrrolidine. First, for obtaining calibration sets, 1 μL of solutions containing compounds (2) and (3) in chloroform with concentrations ranging from 1.0 to 8.0 mM were applied separately on chromatographic plates. In the kinetic study, 100 μL of a solution of compound (1) in chloroform (0.32 M) was added to 100 μL of pyrrolidine in chloroform (1 M eq). 10 μL of the reaction media taken at different times (30, 60, 90, 120, 180, 240, 300, 600, 1200 and 1800 s) was applied onto the TLC layer and separated with chloroform. All the final chromatograms were directly scanned to generate their digital image. Detection by absorbance measurement at 411 nm for (2) and 331 nm for (3). Kinetics profile was constructed for reagent (2) consumption and product (3) formation.

Chromatographia 20, 99-101 (1985). TLC of food dyes, indigo carmin, cochineal red, acid amaranth I, orange yellow S and tartrazine G on thin MgO layers with mixtures of 15 % sodium citrate and methanol in proportions from 9:1 to 1:9. The best proportion of the developing solvent mixture was 6:2. It permits the full separation of the dye mixture from a 0.3 mL sample solution with concentrations of 1 x 10 to minus 6 mole/liter.