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%.

TLC in pharmacy: erythromycin. Deutsche Apotheker Zeitung 131, 2710-2711 (1991). TLC of erythromycin on silica with methanol – ethyl acetate 9:1. Visualization by spraying with ammonium-8-anilinonaphthaline-1-sulfonate, heating at 80 °C for some min and under UV 365 nm or by spraying with K2Cr2O7 – sulfuric acid reagent, heating at 90 °C for some min; observation under day light.

J. Planar Chromatogr. 5, 200-204 (1992). TLC of red bell pepper extract and ß-carotene on silica with ethyl acetate - dichloromethane - hexane 24:56:20 (single development); and a variety of solvent combinations (multiple development); scanning at 450 nm (absorbance). The results show a general instability of carotenoids under conditions typically employed in TLC. Rigorous exclusion of oxygen and light would prevent the alteration of carotenoids, however, not particularly easy to achieve in practice. The use of layers impregnated with antioxidant is one possible solution. Great caution should be exercised when reviewing data TLC for the identification and quantification of carotenoids from plant material.