leaves. J. Planar Chromatogr. 31, 377-381 (2018). HPTLC of ursolic acid and β-sitosterol in the leaves of Paederia foetida on silica gel with toluene ‒ ethyl acetate ‒ formic acid 80:20:1. Detection by spraying with anisaldehyde–sulfuric acid reagent, followed by heating at 110 °C for 1 min. Quantitative determination by absorbance measurement at 550 nm. The hRF values for (1) and (2) were 22 and 38, respectively. Linearity was between 100 and 500 ng for (1) and (2). LOD and LOQ were 40 and 121 ng for (1) and 50 and 152 ng for (2). The intermediate precision was <2 % (n=3). Recovery ranged from 97.2 % to 99.2 % for (1) and 98.0 % to 99.2 % for (2).

J. Chromatogr. Sci., 56 (9), 846–852 (2018). Simultaneous determination of theophylline (THP), guaifenesin (GUI) and guaiacol (GUA, a guaifenesin impurity) by HPTLC on silica gel with ethyl acetate – hexane – methanol - ammonia 65:35:10:2. Detection and quantification by densitometry at 275 nm. The hRf values were 13, 35 and 80 for THP, GUI and GUA, respectively. The linearity range was 0.4–2 μg/band for both THP and GUI, and 0.4–1.2 μg/band for GUA. Validation of the proposed method according to ICH guidelines. Statistical comparison of the results with RP-HPLC showed no difference regarding accuracy and precision.

VII. Comparison of analytical methods for determination of impurities in tetracycline pharmaceutical preparations. J. Chromatogr. 314, 303-311 (1984). HPTLC of various tetracyclines on silica with acetone - 5 % aq. sol. of Na2 EDTA 10:1 and RP-TLC on C18-plates with methanol - acetonitrile - 0.5 M oxalic acid (aq. pH 2.0) 1:1:4 or 1:1:2. Detection by UV 366 nm or with 0.5 % Fast Violet B aq. solution and pyridine. Quantification by scanning at the dual-wavelength mode at 366/600 nm for 4-epitetracycline and chlortetracycline and at 425/650 nm for anhydrotetracycline and 4-epianhydrotetracycline. RP-TLC-densitometry appears to be a precise method for the determination of tetracyclines.

V. Danube Symposium on Chromatography, Yalta, November 11.-16., 1985. TLC of phospholipids on silica with chloroform - methanol - water 65:25:4, identification of phospholipids using Bartlet's method.

J.A.O.A.C. 69, 173-177 (1986). TLC of ampicillin on silica with butanol - acetic acid - water 4:1:1. Detection by UV followed by spraying with 0.2 % ethanolic ninhydrin solution.

Quantitative determination of TLC-separated enantiomers. GIT Suppl. Chromatographie 3, 27-32 (1987). By means of nine examples (D-Phe, tert.-leu, 5, 5-dimethyl-thiazolidine-4-carboxylic acid, O-Bzl-Ser, L-4-iodophenylalanine, L-he, L-tyr, L-methyldopa, D-leu-L-leu) is demonstrated, that the quantitative determination of TLC-separated antipodes is a useful method for daily routine process in any laboratory. The resolution of the enantiomers is excellent, the respective antipodes could be evaluated at trace levels, the limit of determination is found to be at or above 0.1 %. In comparison to the "classical methods" GC and HPLC, TLC offers separation in parallel runs.

Synthesis and binding studies. J. of Medicinal Chemistry 31, 893-897, (1988). TLC of substituted 4-hydroxy-butyric acids on silica with ethyl acetate - hexane 1:2. Detection by exposing to iodine vapor.

Proc. 6th Int. Symp. Instrum. Planar Chromatogr., (Interlaken 1991), Inst. Chromatogr., Bad Dürkheim, FRG, 37-39 (1991). TLC of fluphenazine-4-chloro-phenoxy-i-butyric ester in sesame oil on silica with two consecutive developments; 1) benzene - acetone 4:5, 2) ethyl acetate- methanol - diethylamine 80:10:5. Visualization under UV 245 nm. Densitometry by absorbance at 260 nm. Standard deviation of the linear calibration curve (0.5 - 3.0 µg) ranged between 2-3%.