J. Chromatogr. 347, 303-309 (1985). Study on HPTLC behaviour of phenylethylamines and phenolic acids on silanized silica impregnated with N-dodecylpyridinium chloride, or with dodecylbenzenesulfonic acid. The presence of KCl makes the spots more compact. The presence of 1 or more OH groups in the molecule decreases the retention of the compounds, whereas an opposite behaviour occurs with replacement of a phenolic group with an OCH3 group. Secondary amines are more strongly retained than primary amines. The N-CH3, groups increase the affinity of the compounds towards the exchanges in the order: primary amine secondary amine tertiary amine. Phenylethylamines, phenolic acids, silanized silica, ammonium tungstophosphate

J. Agric. Food Chem. 34, 633-638 (1986). Separation of -hydroxybutyric acid, succinic acid, beta-phenylacetic acid on silica with toluene - ethyl formate - formic acid 5:4:1. Detection by UV 254 nm. After extraction HPLC determination.

J. China Assoc. Inst. Anal. 6, 19-22 (1987) (Fenxi Ceshi Tongbao). TLC on silica with chloroform - methanol - acetic acid - water 80:10:8:2. Detection by exposing to iodine vapour. Quantification by densitometry at 520 nm.

Analyst 112, 1663-1665 (1987). TLC on silica with chloroform - methanol 85:15. Detection under UV 366 nm. Quantification by densitometry.

J. Planar Chromatogr. 2, 65-70 (1989). For qualitative analysis monodansyl cadaverine (MDC) was employed without further purification. Column-chromatographic purification is recommended for the quantification of short chain carboxylic acids. For in situ derivatization the carboxylic acid sample solutions were applied to the HPTLC plates as bands with a maximum length of 10 mm. These were then „overlayed“ with MDC solution containing N,N’-dicyclohexylcarbodiimide to activate the acids. Short-chain carboxylic acids were separated on normal silicagel phases with toluene - ethyl acetate - ammonia mixtures as mobile phase. Stepwise and gradient developments allow the baseline separation. Long-chain carboxylic acids are better separated on RP-18 phases with acetonitrile-tetrahydrofuran mixtures and methanol as mobile phase.

Chromatographia 32, 307-316 (1991). HPTLC on NH2-bonded silica with different solvent systems. Detection by heating at 150 °C. Quantification by densitometry in fluorescence mode at 366 nm. The detection limits in any case, below the physiological range.

Chromatographia 35, 627-630 (1993). TLC separation of free fatty acids into two fractions, a more mobile group of saturated and monounsaturated fatty acids and a less mobile group containing polyunsaturated fatty acids, on silica with hexane - acetic acid - water 50:2:1. Detection by exposure to iodine vapor, and under UV 254 nm. Determination of polyunsaturated fatty acids by HPLC.

by thin-layer chromatography.) (Chinese). Chinese J. Pharm. Anal. (Yaowu Fenxi Zazhi) 15, 30-32 (1995). TLC of ursolic acid on silica with toluene - ethyl acetate. acetic acid 60:25:3. Detection by spraying with 10% sulfuric acid in ethanol and heating at 105 °C for 5 min. Quantification by fluorodensitometry at 365 nm.