Planta Med. 75, 711-718 (2009). For many decades, planar chromatography has been used for the analysis of plants, in particular today in its most advanced form of HPTLC. The technique is e. g. used for the identification of medicinal plants and dietary supplements, and for the detection of adulteration and quantitative determination of marker substances. Reliable qualitative and quantitative results can be achieved based on suitable instrumentation and adequate methodological concepts. The manageability of the entire planar chromatographic process has improved. Integration of biological detection systems as well as hyphenation to mass spectroscopy has widened the applicability of planar chromatography as an important analytical technique. The introduction is followed by explanation of HPTLC, use of HPTLC in plant analysis, limitations, applications (identification, detection of adulteration and quantitation), and instrumentation (chromatogram development, documentation, detection and evaluation).

J. Planar Chromatogr. 24, 320-324 (2011). TLC of a red wine sample and gallic acid, caffeic acid, chlorogenic acid, p-coumaric acid, and quercetin as standards on silica gel with toluene - ethyl actate - formic acid 6:5:1 with chamber saturation for 1 h. Detection by treatment with 1 % methanolic diphenylborinic acid 2-aminoethyl ester (natural products reagent) followed by 5 % ethanolic polyethylene glycol. Evaluation under UV light at 254 and 366 nm. Also spraying with 0.04 % methanolic DPPH radical reagent. The hRf value was 65, 60, 56, 47, and 7 for p-coumaric acid, quercetin, caffeic acid, gallic acid, and chlorogenic acid, respectively.

J. Ethnopharmacol. 139, 142-148 (2012). HPTLC of 1,2-dihydroxy-3-pentadec-8-enylbenzene (A) and 1,2-dihydroxy-3-pentadeca-8,11-dienylbenzene (B) in the fruits of Semecarpus anacardium L. f. (Anacardiaceae) on RP-18 with acetonitrile - water 199:1. Detection by spraying with anisaldehyde - sulfuric acid reagent. The hRf values of (A) and (B) were 31 and 42, respectively. The method was combined with ESI-MS and NMR for compound identification.

J. Planar Chromatogr. 23, 348-352 (2010). TLC of methoxylated flavones G1, G2, G3, G4 (3’,4’,5’-trimethoxyflavone), and G5 on alumina with n-hexane - ethyl acetate 7:3 at ambient temperature with chamber saturation. Detection by visual inspection at 365 nm. The hRf values of G1 (monomethoxyflavone), G2 (monomethoxyflavone), G3, G4 (trimethoxyflavone), and G5 (dimethoxyflavone) were 42, 30, 22, 17, and 12, respectively.

CBS 107, 11-12 (2011). HPTLC of tiliroside on silica gel with ethyl acetate - formic acid - acetic acid - water 100:11:11:27 + 1 % heptane. For quantification determination by densitometry in absorbance mode at 315 nm. For side component analysis detection by spraying with natural products reagent and evaluation under UV 366 nm, and by spraying with anisaldehyde reagent followed by heating for 15 min at 90-125 °C and evaluation under white light. The presence of relevant side components (e.g., coumaric acid, kaempferol and glucose) could be excluded.

native to southern Italy (Salento). Planta Med. 77, 287-292 (2011). TLC of glucosinolates (e. g. glucoraphanin, glucoiberin, gluconapin, progoitrin, glucoerucin, desulphosinigrin, sinigrin, glucobarberin, gluconasturtin, glucobrassicin, neoglucobrassicin, 4-methoxyglucobrassicin, and 4-hydroxyglucobrassicin) and extracts of leaves and inflorescences of the „mugnolo“ on silica gel with 2-propanol - ethyl acetate - water 7:1:2. Detection under UV 254 and 366 nm and by spraying with phosphomolybdic acid hydrate (10 % in ethanol).

Volumes 1-3, CBS Publishers & Distributors, New Delhi, India (2013). The first volume provides a comprehensive introduction to the HPTLC technique, including details for each HPTLC step as well as various factors which influence the performance of a HPTLC analysis. Then presented over 3 volumes, 528 protocols for the HPTLC analysis of pharmaceutical formulations follow. Each protocol provides details on the preparation of samples and standards, chromatographic equipment, parameters for densitometric evaluation, chromatographic conditions, including stationary phase, mobile phase, standard and sample application, chamber saturation, relative humidity, quantity of mobile phase, temperature, migration distance and other critical parameters. References to the original publication are given as well as comments on the validation or any comparative study. Each protocol is illustrated with a typical densitogram, structures of the compounds analysed and overlaid UV spectra of compounds analysed (for selection of suitable wavelength for densitrometric scanning). All in all a comprehensive collection of protocols for pharmaceutical formulations.

J. Planar Chromatogr. 25, 468-470 (2012). TLC of mannosylerythritol lipids (1), monoacylglycerol (2) and triacylglycerols (3) on silica gel with a mixture of formic acid 0.4 % in diethyl ether. The hRf values of (1) were 3, 6 and 11, whereas the hRf of (2) and (3) were 71 and 98, respectively. The method for analysis of biosurfactants allowed to discriminate mannosylerythritol lipids and acylglycerols.