Indian Drugs 42 (10), 650-653 (2005). A simple rapid, precise and cost-effective HPTLC method has been developed for the determination of ursolic acid in Oscimum sanctum (Tulsi) leaves and its formulations (Tulsi ghan tablets and Tulsi capsules). HPTLC on silica gel with toluene - ethyl acetate - acetic acid 30:3:1. Detection with anisaldehyde in sulphuric acid reagent followed by heating in an oven at 110 °C. Quantitative determination by absorbance measurement at 580 nm. Linearity of the detector response was given in the range of 40 - 280 ng. LOD was 8 ng. The correlation coefficient obtained from linearity was 0.9985. The standard error was 26.511. The mean assay values of ursolic acid wa found to be 3.485 mg/g, 0.553 mg/g and 3.221 mg/g in tulsi ghan tablets, tulsi capsule and tulsi leaves respectively.

Abstract GP-75, IPC (2005). HPTLC of satranidazole and its degradation products on silica gel with toluene - acetonitrile 3:2. For stability studies, the sample was treated with NaOH, HCl, H2O2 and photolysis. Degradation products were well resolved with significant different Rf values. The method had a linearity range of 100-500 ng. The proposed method suitable to investigate the kinetics of hydrolysis and photodegradation processes with first order in NaOH, and zero order for photolysis.

Indian J. Pharm Sciences 67 (6), 721-726 (2005). HPTLC of gallic acid in ethanolic extracts of rhizomes from curculigo orchioides on silica gel with toluene - ethyl acetate - acetic acid 25:15:1. Quantitative determination by absorbance measurement at 260 nm. The method was validated according to ICH guidelines. Rhizomes and their marketed formulation were found to contain 2.5 % and 5.0 % of gallic acid.

J. Anal. Chem. 59 (4), 348-353 (2004). Demonstration of quantitative analysis using the software processing of scanned chromatogram images for e.g. food dyes. Digitalization of chromatograms obtained by scanning with a flatbed scanner using the special-purpose software for quantitative analysis.

J. Chil. Chem. Soc. 48, 19-23 (2003). HPTLC validation of atrazine in aqueous extracts of soils on silica gel (layer thickness 100 µm) previously activated at 120 ºC for 30 min. The elution program applied to aqueous soil matrices started with 10 short isocratic runs (0.8 min) with acetonitrile – dichloromethane 30:70. Mixer was emptied after the tenth step and refilled to continue with 4 successive isocratic runs (2.5, 5.0, 7.5 and 25 min) with dichloromethane. The plate was dried for 1 min between each step and for 3 min after the last one. The plate was preconditioned with nitrogen for 15 s before each run. Quantitative determination by absorbance at 210 nm. Linearity is between 5 and 100 ng and recoveries ranging from 98.7 to 103.5 %. The detection limit is 1.5 ng and the quantification limit is 4.9 ng. Precision analysis shows an intra-assay variation between 1.48 and 5.47 %. The method can be applied to a broad range of soils including those with high organic matter content.

J. Sep. Sci. 26, 1698-1700 (2003). HPTLC of levofloxacin and lamotrigine (internal standard) on silica gel with water – methanol – n-butanol 1:1:1 and 1 drop of ammonia. Quantitative determination by absorbance measurement at 298 nm. Linearity of determination of levofloxacin is between 0.8 and 3.0 µg and its average percentage recovery is 99.9 %.

J. Planar Chromatogr. 19, 355-360 (2006). OPLC of paracetamol, acetylsalicylic acid and caffeine on HPTLC silica gel (prewashed with acetonitrile - water 17:3) with n-hexane - toluene - diethyl ether - glacial acetic acid - methanol 100:50:30:19:1 and toluene - diethyl ether - glacial acetic acid - methanol 50:30:19:1. Quantitative determination by absorbance measurement at 254 nm.

J. Liq. Chromatogr. & Relat. Technol. 29, 2159-2165 (2006). HPTLC of beta-carotene and lutein on RP-18 (prewashed with dichloromethane - methanol 1:1) with petroleum ether (35-55°C) - acetonitrile - methanol 1:1:2 in a twin-trough chamber with chamber saturation for 15 min. Evaluation under white light. Experiments were done rapidly in subdued light to prevent pigment degradation. Quantification by densitometry at 448 nm for lutein and 455 nm for beta-carotene.