J. Planar Chromatogr. 32, 41-46 (2019). HPTLC of ayapanin in the leaves of Ayapana triplinervis on silica gel with ether - ethyl acetate 3:2. Quantitative determination by absorbance measurement at 254 nm. The hRF value of ayapanin was 56. Linearity was between 200 and 1000 ng/zone. The intermediate precision was below 0.8 % (n=6). The LOD and LOQ for ayapanin were 54 and 169 ng/zone, respectively. Recovery rate was 99.7 % for ayapanin.

J. Chromatogr. A 1043 (1-2), 243-251 (2007). Presentation of the coupling of planar chromatography with direct analysis in real time time-of-flight mass spectrometry (DART-TOF-MS) for the first time. By cutting the plate within a track led to substance zones positioned on the plate edge, the interested zones were directly introduced into the DART gas stream to obtain the mass signals instantaneously within seconds, giving the detectability in the very low ng/zone-range on the example of isopropylthioxanthone. The coupling was perfectly suited for identification and qualitative purposes, but for quantification of results the analytical response and the repeatability were strongly dependent from proper manual positioning of the HPTLC plate into the excited-state gas stream of the ion source. By using stable isotope-labeled standards the drawback can be overcome demonstrated with the example of caffeine, and the analytical response (r2 of 0.9892) and repeatability (RSD < ±5.4%, n = 6) were improved to a high extent. The spatial resolution by an in-house-built plate holder system was shown to be better than 3 mm; the decay of the signal was observed. Comparison of the efficacy of this new coupling to a plunger-based extraction device for HPTLC/electrospray ionization–MS. The detectability of latter showed to be down to the pg/zone-range, e.g. the limit of quantification for isopropylthioxanthone to be 100 pg/zone. The repeatability was comparable (RSD ± 6.7%), however, without the need of internal standard correction, and the analytical response slightly better (r2 of 0.9983). The spatial resolution was 2 mm or 4 mm depending on the plunger head used.

J. Sep. Sci. 30, 2053-2058 (2007). HPTLC of umbelliferone (1), psoralen (2), and eugenol (3) in the dried fruit pulp of Aegle marmelos and in the fruit of Trachyspermum ammi and Foeniculam vulgare on silica gel with toluene – methanol 19:1. Quantitative determination by absorbance measurement at 331 nm for (1), 304 nm for (2), and 280 nm for (3). The hRf values were 30, 58, and 70 for (1), (2), and (3), respectively. Linearity was between 1 and 5 ng/zone, 16 and 96 ng/zone, and 200 and 1000 ng/zone for (1), (2), and (3), respectively. The limits of detection and quantification were 0.8 and 1.2 ng/zone for (1), 8 and 16 ng/zone for (2), 60 and 150 ng/zone for (3), respectively. Recoveries were 98.9 %, 100.1 %, and 99.3 %, for (1), (2), and (3) respectively.

J. Sep. Sci. 30, 1893-1898 (2007). HPTLC of L-DOPA in tablets on silica gel with acetone – chloroform – n-butanol – acetic acid glacial – water 12:8:8:8:7. Quantitative determination by absorbance measurement at 497 nm. The hRf value of L-DOPA was 37 and selectivity regarding matrix was given. Linearity was between 100 and 500 ng/µL. The intra-assay variation was between 0.26 and 0.65 % and inter-assay variation was between 0.52 and 2.04 %. The limits of detection and quantification were 1 and 3 ng/µL, respectively. No significant difference was found between this method and the official HPLC method.

CBS 98, 2-4 (2007). HPTLC of amino-3-propan-1-ol, a degradation product of dexpanthenol, on silica gel with ethanol - water - acetic acid 16:3:1. To the mobile phase the derivatization reagent was added, i.e. 0.5 g ninhydrin were dissolved in 100 mL solvent mixture. Development in the horizontal developing chamber from both plate sides over 40 mm. Detection by heating at 105 °C for 5 min. Quantitative determination by absorbance measurement at 486 nm. The hRf value of amino-propanol was 50. The mean repeatability was 4.9 % at 5 different concentration levels. The relative standard deviation of the intermediate precision (n=9) was 5.7 %. The limit of detection and quantification was 4.5 µg/mL and 15 µg/mL, respectively (related to the application volume of 2 µL). Recovery (n=15) was 102 %.

Chromatographia 66 (9-10), 801-804 (2007). HPTLC of withaferin A and withanolide A in Withania somnifera methanolic extract from different plant parts (leaf, root, stem and fruit) and of two morphotypes, on silica gel with toluene - ethyl acetate - formic acid 5:5:1. Quantification by densitometry in absorption mode at 530 nm. Linearity was between 200 and 3200 ng for both withaferin A and withanolide A. The average recovery of withaferin A and withanolide A was 96.0 and 96.7 %.

J. Planar Chromatogr. 21, 89-96 (2008). TLC of dyes in normal-phase systems on silica gel, diol phase, cyano phase, and amino phase, and in reversed-phase systems on cyano phase, Diol phase, amino phase, and RP-18. RP chromatography with different mobile phase modifiers (THF, dioxan, methanol, acetonitrile, and acetone) at different concentrations, containing different amines, cationic and anionic ion-pair reagents, buffers, and ammonia, again at different concentrations. Based on the results the best system was selected: HPTLC of tartrazine, sunset yellow FCF, allura red AC, ponceau 4R, brilliant blue FCF, indigotine, brilliant black PN, quinoline yellow, patent blue V, brilliant green BS, azorubin, and brown HT on RP-18 with acetate buffer pH 3.5 containing 15-25 % modifier and 0.025 M propylamine or diethylamine. Detection in white light and under UV 254 and 366 nm. Quantitation by diode array densitometry in the range of 191 to 1033 nm.

J. of Pharm. Biomed. Anal. 44 (3), 812-817 (2007). HPTLC of extracts of Notopterygium incisum Ting ex H.T. Chang (or Notopterygium forbesii Boiss) root and rhizome, and marker compounds isoimperatorin, notopterol and bergapten. The authentication of rhizoma et radix Notopterygii was achieved by comparing the colors and Rf values of the bands in TLC fingerprints with those of the marker compounds. The HPLC fingerprints of 16 batches of herbal samples from different regions of China showed similar chromatographic patterns. Five peaks were selected as characteristic peaks, and three of these were identified by using LC-MS-MS techniques.