J. Planar Chromatogr. 23, 108-111 (2010). HPTLC of gallic acid, ferulic acid, syringic acid, catechin, protocatechuic acid and vanillin on silica gel with toluene - ethyl acetate - formic acid 8:2:1 in a twin-trough chamber previously saturated for 15 min. Quantitative determination by absorbance measurement at 280 nm. Accuracy was between 96.3 and 90.7 %, repeatability between 0.65 and 0.93 %, inter-day precision between 0.80 and 0.90 %, intra-day precision between 0.72 and 0.95 %, and precision between 0.87 and 0.92 %. LOD and LOQ were about 100 and 400 ng/band, respectively. Starting at LOQ, the correlation coefficients were between 0.988 and 0.997.

Asian Journal of Chemistry 23(1), 469-470 (2011). Several herbal formulations were analyzed for gallic acid contents. Tablets were powdered, subjected to hydrolysis by refluxing with 10 % HCl, filtrated and extracted with chloroform. Acidic aqueous extracts were concentrated and the residue was taken up in methanol. TLC on silica gel with ethyl acetate - formic acid 85:11. Gallic acid was observed at an hRf value of 89. Densitometric quantification of gallic acid at 272 nm. The method was linear in the range of 100-3000 ng/band. The method was suitable for analysis of formulations without interference from excipients. Gallic acid contents of different tablet samples varied from 0.06-0.15 % w/w.

Anal. Chim. Acta 690 (2), 148-161 (2011). Chromatographic fingerprinting has been generally accepted as analytical method for the quality control of herbal medicines. This review describes the evolution of the regulations and guidelines on the quality control of herbal medicines, and reviews the established analytical techniques in TLC, HPLC, UHPLC, hydrophilic interaction chromatography, and GC. Emphasis is put on the most recent developments, such as miniaturized techniques, new stationary phases, analysis at high temperatures and multi-dimensional chromatography. The new chemometric data handling techniques are discussed.

J. Chem. Pharm. Res. 2(1), 155-161 (2010). A chroman derivative (C16O4H22) was isolated from the ethanolic extract of dried seeds of Ensete superbum. HPTLC on silica gel with toluene – ethyl acetate – formic acid 5:4:1. Quantitative determination by absorbance measurement at 254 nm. The linear range was 300-900 ng/band. The amount of the chroman in different fractions of the extract was 1.83 % (ethanol fraction), 1.74 % (ethyl acetate fraction) and 0.74 % (methanol fraction).

J. of Chromatogr. A 1218 (19), 2820-2825 (2011). A unified procedure for image preprocessing of 2D TLC videoscans saved as JPG files is proposed for further supervised or unsupervised chemometric analysis. The procedure was based on open source software and included denoising using a median filter, baseline removal with the rollerball algorithm and nonlinear warping using spline functions. The application of the proposed procedure enabled filtration of random differences between images, such as changes in the intensity of the background as well as differences in the location of the zones. After the preprocessing only the zone intensity had an influence on the statistical analysis by principal component analysis (PCA) or other techniques. The proposed technique was successfully applied for the determination of the differences between three Carex species based on the 2D videoscans of the extracts.

J. Planar Chromatogr. 23, 323-325 (2010). HPTLC of taraxerol on silica gel with hexane - ethyl acetate 9:1 in a saturated twin-trough chamber. Detection by spraying with anisaldehyde - sulfuric acid reagent followed by heating for 5 min at 80 °C. Quantitative determination by absorbance measurement at 540 nm. The average recovery was between 99.6 and 100.3 % with %RSD less than 2 %. For both intra-day and inter-day precision %RSD was less than 2 %. The LOD and LOQ were 47 and 140 ng/band, respectively. The linearity range was 0.5-2.5 µg/band. The hRf value of taraxerol was 22.

J. Planar Chromatogr. 24, 376-380 (2011). HPTLC of stem bark extracts from D. melanoxylon and lupeol and betulin on silica gel, prewashed with methanol, with ethyl acetate - hexane 9:41 with chamber saturation for 3 min at 29 +/- 4 °C and 65 +/- 5 % relative humidity. The hRf value was 46 and 25 for lupeol and betulin, respectively. Quantitative determination by densitometry in absorption mode at 560 nm for lupeol and 510 nm for betulin. Detection by derivatization with 5 % methanol-sulfuric acid reagent. The LOD and LOQ was 40 and 100 ng/zone for lupeol and 50 and 100 ng/zone for betulin, respectively. The instrument precision and repeatability (n = 6) were 0.8 and 1.3 % for lupeol and 1.1 and 1.2 % for betulin, respectively. The linearity range was 100-500 ng/zone for both lupeol and betulin. The intra-day and inter-day precision was 1.1-1.7 % and 1.3-2.0 % for lupeol and 0.8-1.9 % and 1.9-2.2 % for betulin.

J. Liq. Chromatogr. Relat. Technol. 32, 2893-2905 (2009). HPTLC of albiflorin, paeoniflorin, (beta)-catechin, benzoyloxypaeoniflorin, benzoylpaeoniflorin, beta-sitosterol in the roots of Radix paeoniae Rubra (1) and Radix Paeoniae Alba (2) on silica gel with chloroform - ethyl acetate - methanol - formic acid 30:5:10:1 for high polarity components and toluene - ethyl acetate - methanol - formic acid 20:4:2:1 for lipophilic components. Detection by spraying with vanillin - sulphuric acid - ethanol 1:5:95, followed by heating at 105 ºC for 10 min. Qualitative determination by densitometry at 366 nm. The HPTLC fingerprints allowed differentiation between the roots of (1) and (2).