I. Classification procedure by thin-layer chromatography.) Classification of pesticides, hypnotics, psychotropics, narcotics, local anesthetics etc. by their Rf values related to standard markers on silica TLC. The standard markers used: methyl yellow, methyl red, tetrabromophenol phthalein ethyl ester, malachite green and rhodamine B.

Chinese J. Chromatogr. (Sepu) 9, 113-116 (1991). TLC on silica with isopropanol - acetic acid - water 14:1:5. Detection by dipping into a solution of potassium hydroxide in ethanol and heating at 160 °C for 10 min. Quantification of fluoro densitometry at 230 nm. Detection limit 40 ng. The calibration curve was linear over the range of 40 - 350 ng with the correlation coefficient of 0.998.

Part 3. Identification of drugs and their metabolites by PCA of standardized TLC data. J. Planar Chromatogr. 7, 233-241, (1994). Principal components analysis of standardized Rf values of 443 drugs and their metabolites chromatographed with four eluent systems provided a two-component model accounting for 70.8% of the total variance. The "scores" plot enabled either identification, or restriction of the range of inquiry to few candidates. This simple, cheap and fast analytical method is of vital importance in the identification of an unknown drug in cases of overdose intoxication or poisoning, and is particularly valuable in the unaided search for drugs and their metabolites in instances when the substance is very polar and cannot be identified by gas chromatography.

Proc. 9th Internat. Symp. Instr. Chromatogr., Interlaken, April 9.-11., 155-159 (1997). HPTLC of D/L- methadone and L-methadone on diol with toluene - hexane - diethylamine 3:6:1. Detection by derivatization with modified Dragendorff reagent; quantification by densitometry at 254 nm.

J. Chromatogr. B 751 (1), 19-27 (2001). TLC on silica gel with hexane - toluene - diethylamine 13:4:1. Quantitation by densitometry at 234 nm. Evaluation of the accuracy, precision, detection and quantitation limits of the methods by comparison with HPLC.

Biomed. Chromatogr. 20 (2), 151-153 (2005). TLC of the four principal triterpenoid components of Centella asiatica on silica gel plates with the combination of ethyl acetate and methanol. Detection by spraying with anisaldehyde solution, followed by heating at 100 °C for 5 min. Evaluation under white light. The developed method is a modification of the method described in the European Pharmacopoeia (5th edn). Confirmation of the separated compounds by MALDI-TOF mass spectrometry.

J. Planar Chromatogr. 20, 197-202 (2007). HPTLC of guggulsterone E and Z on silica gel prewashed with methanol with petroleum ether - ethyl acetate - formic acid 30:10:1 in a twin-trough chamber saturated for 20 min. Detection and densitometric scanning at 254 nm.

iNDIAN dRUGs 44(8), 632 (2007). TLC, HPTLC and NMR spectroscopic methods are reported for identification and characterization of aloin isolated from Kumariasava and Aloe vera. TLC and HPTLC of chloroform extracts on silica gel with chloroform - ethyl acetate 3:1. Detection under UV 366 nm. The hRf value of aloin was 84.