Phosphorus, Sulfur Silicon Relat. Elem. 184, 1139-1148 (2009). The new TLC system for sulfide ions detection is based on the use of 2,4,6-triphenylpyrylium salts as pre-chromatographic derivatization reagents. The cations L1 (2,4,6-triphenylpyrylium) or LN1 (4-[p-(N,N-dimethylamino) phenyl]-2,6-diphenylpyrylium) were used in the derivatization reactions in a tube or directly on the TLC plate before the developing step. TLC of L1 on silica gel with methanol – dichloromethane 1:5. TLC of LN1 on cellulose with phosphoric buffer (pH 6.0) – acetonitrile – 1,4-dioxane 4:2:1. The detection procedure allows selective and sensitive detection for sulfide anions at several dozen pmol/spot.

J. Chromatogr. A, 1572, 145-151 (2018). Introduction of on-surface reactions as a new strategy for rapid structure elucidation. This was illustrated by a miniaturized on-surface synthesis-guided identification of two new degradation products (impurities) occurring in a pharmaceutical formulation of the anti-cancer drug ifosfamide, especially in the presence of urea. The respective reagents were applied in the nanomole scale accurately and automated on a HPTLC silica gel plate. After a fast reaction in the start zone, the plate was developed, followed by online elution to high-resolution MS, whereby the on-surface reaction highlighted the impurities. As proof of concept and for benchmarking, it was compared to a reaction mixture obtained from conventional preparative synthesis in a round-bottom flask as well as to different formulations. Image evaluation was performed by videodensitometry. Discussion of the advantages such as: 1) the combination of all relevant steps on one HPTLC plate and its resulting efficiency made surface synthesis on chromatographic phases an optimal tool for signal highlighting in MS, and thus for the assignment of impurities in drugs; 2) the miniaturization of the chemistry process scale down to the μg-level per synthesis (in total 30-60 μg chemicals/reaction), setting a new state-of-the-art standard; 3) the contribution to a greener chemistry by reducing the consumption of chemicals and enhancing the analytical efficiency, when adapted for the quality control of any other chemical product.

Chromatographia 21, 599-600 (1986). TLC of non-steroidal anti-inflammatory agents on silica with chloroform - methanol 25 % NH3 80:15:5. Detection by spraying with 0.1 % 9-isothiocyanotoacridine derivatives in dichloromethane or benzene and irradiating with UV 254 and 366 nm. Detection limit 0.1 mg.

Analyst 115, 263-267 (1990). Evaluation of diazonium reagent Fast Black K salt for visualization of amines and phenols on silica plates. Differentiation between aliphatic primary and secondary amines by color. Determination of the structures of colored reaction products. Detection limit 0.05 – 0.5 µg for various chromatographed drug substances.

Bunseki Kagaku (Jap. Anal. Chem.) 42, T143-146 (1993). Description of a method for fluorescence enhancement of spots on TLC plate by wrapping a silica plate with a transparent poly(vinylidene chloride) film just after development, and vaporizing the solvent of the plate with hot air for 15 min. The detection limits of N-dansyldiethylamine, 15 pmol per spot. Application of the method to other plates, such as RP-8 or RP-18, as well as to different solvents, such as benzene, chloroform, and 1,2-dichloroethane, and to the fluorescence compounds such as N-dansylamide, N-dansylhexylamine and dansylglycine.

J. Chromatogr. Sci. 35, 156-160 (1997). Presentation of a simple empirical procedure for optimizing TLC mobile phases, based on an adaptation of the window diagrams technique and requires only a limited amount of data because acceptably accurate intermediate capacity factors and spot width values can be estimated from three initial experiments.

J. Chromatogr. A, 915 (1/2), 217-223 (2001). TLC on silica gel with chloroform - methanol 4:1. Detection by spraying with the substrate, dye and enzyme (Eltman's reagent). The advantages of the procedure were that the known inhibitor, galanthamine could be dereplicated at an early stage of the isolation procedure, and there in no disturbance from sample. Detection limits were found to be between 10 - 200 ng for several known acetylcholinesterase inhibitors tested. Comparison with Dragendorff's detection reagent.

J. Chromatogr. Sci. 46 (6), 560-564 (2008). Quantitative TLC is performed with a digital imaging system with simple equipment and software. The method was used for the quantitative assay of cichoric acid in Echinacea purpurea. TLC on polyamide phase with chloroform - methanol - formic acid - water 3:6:1:1. Detection by spraying with 3 % aqueous aluminum chloride solution. Images of chromatograms were acquired with a standard digital camera under a UV lamp at 365 nm in a dark room. The three-dimensional grayscale digital image dataset (x, y, gray) was reduced to a two-dimensional dataset (distance, accumulative gray) and then plotted as a curve. For quantification the area under the curve (corresponding to cichoric acid) was integrated.