J. Planar Chromatogr. 24, 57-59 (2011). HPTLC of piperine on silica gel with toluene - ethyl acetate - diethyl ether 6:3:1 in a saturated twin trough chamber. The hRf of piperine was 40. Quantitative determination by densitometry at 337 nm. Linearity was between 15 and 75 ng/zone. LOD and LOQ was 5 and 15 ng/zone, respectively. The recovery was 94.5 %. The instrumental precision, repeatability, intra-day and inter-day precision (%RSD, n = 6) was 0.6 %, 0.8 %, 0.9 and 0.8 %, respectively.

J. Planar Chromatogr. 24, 257-263 (2011). HPTLC of hydrophilic and lipophilic constituents of Salvia miltiorrhiza and standards protocatechuic acid and aldehyde, salvianolic acid A and B, dihydrotanshinone I, rosmarinic acid, caffeic acid, cryptotanshinone, tanshinone II A, tanshinone I, and miltirone on silica gel with dichloromethane - ethyl acetate - formic acid 11:12:5 for the first development and petroleum ether - ethyl acetate - cyclohexane 15:11:14 for the second development with chamber saturation for 30 min. The first mobile phase separated the hydrophilic constituents salvianolic acid B, salvianolic acid A, rosmarinic acid, caffeic acid, protocatechuic acid, and protocatechuic aldehyde. Detection under UV light at 254 and 365 nm. After documentation the plates were placed in a second chamber and development with the low polarity mobile phase which separated dihydrotanshinone I, cryptotanshinone, tanshinone I and II A, and miltirone. Detection under UV light at 254 and 365 nm. Quantitative determination by densitometry in absorbance mode at 260 or 290 nm. The linear range was between 0.1-0.3 and 0.7-8.3 µg/zone. Instrumental precision was less than 4 % (n = 6). Precision on one plate was below 5 % (n = 6) and on different plates below 14 %. Depending on the substance, the limits of detection and quantification were between 14-22 and 69-276 ng/zone, respectively. The repeatability (n = 6) was between 1.3-3.4 %. Some of the compounds had similar hRf values: for rosmarinic acid 44, for salvianolic acid 43, for caffeic acid 49, for protocatechuic acid 49, for dihydrotanshinone 65 and for cryptotanshinone 63. Additional detection by spraying with 5 % sulfuric acid in ethanol.

Research J. Pharm. and Tech. 3(1), 239-243 (2010). TLC of bumetanide in bulk drug and tablet formulation on silica gel with toluene - ethyl acetate - formic acid 14:7:1. The hRf value of bumetanide was 45 and it well resolved from degradation products. Quantitative evaluation by absorbance measurement at 335 nm. The method was linear in the range of 100-800 ng/band. The recovery was between 98.5-99.1 %. The sample was subjected to different stress conditions, e.g. acid, alkali, and photolytic oxidation.

Anal. Chim. Acta 633 (2) 188-196 (2009). HPTLC of lycorine and galanthamine from Narcissus jonquilla ‘Pipit’ on silica gel with chloroform - methanol - 25 % ammonia 18:1:1. Quantitative evaluation by absorbance measurement at 207 nm. The correlation coefficients were r=0.9882 and 0.9908, respectively, for the mean values of galanthamine and lycorine. Investigation of different extraction solvents showed that extraction with methanol and 1 % tartaric acid in methanol at default conditions (120 °C, p = 60 bar, time: 10 min, one static cycle) provide the highest yields of total alkaloids, whereas for toluene the lowest amounts were measured. Lycorine to galanthamine mean ratios were dependant on the type of solvent used, and in toluene galanthamine and related alkaloids were preferably extracted.

Asian Journal of Chemistry 23 (5), 2098-2100 (2011). HPTLC of glycyrrhizic acid in herbal formulation on silica gel with chloroform - glacial acetic acid - methanol - water 15:8:3:2. The hRf value of glycyrrhizic acid was 28. Quantitative evaluation by absorbance measurement at 254 nm. The method was found to be linear in the range of 100-500 ng/band with average recovery between 99-102 %.

Asian Journal of Chemistry 23(5), 1917-1921 (2011). TLC of concentrated methanolic extracts of a polyherbal ayurvedic syrup formulation (containing vasaka as main ingredient) on silica gel with methanol - toluene - dioxane - 25 % ammonia 2:2:5:1. The hRf value of vasicine was 74. Quantitative evaluation by absorbance measurement at 254 nm using vasicine as marker for standardization of the formulation. The method was found to be linear in the range of 4-12 ng/band. Isolation of vasicine from Adhatoda varica is also described.

Asian Journal of Chemistry 23 (5), 2046-2048 (2011). TLC of alpha- and beta-asarone in Acorus calamus on caffeine modified silica gel (with 10 % caffeine in dichloromethane and dried at 100 °C for 10 min) with toluene - ethyl acetate 93:7. The hRf value of alpha-asarone was 67 and of beta-asarone 77. Quantitative evaluation by absorbance measurement at 313 nm. The linearity was in the range of 50-1000 ng/band for beta-asarone. The alcoholic extracts of samples from different geographical regions were found to contain 0.2-0.8 % of alpha-asarone and 8.7-11.2 % of beta-asarone.

of Chromatogr. A 1231, 59-65 (2012) Reversed-phase HPTLC of lutein, lycopene and beta-carotene standards on RP-18 (pre-washed by development with dichloromethane – methanol 1:1) with methanol – acetone 1:1 with 0.1 % of 2-tert-butylhydroquinone. The hRf value was 4 of lutein esters, 24 of beta-carotene, 32 of lycopene, and 68 of lutein. Quantitative determination of lutein by densitometry at 450 nm. The repeatabilities were %RSD = 3.4, 1.3 and 1.6 at levels of 5 ng, 15 ng and 25 ng, respectively (n = 6). The calibration curve was best fit with a polynomial function in the range of 5-30 ng. The LOD was 1.5 ng, the LOQ 5 ng. With these chromatographic conditions also dietary carotenoids lutein esters, lycopene, free lutein and ß-carotene from food supplements were identified. It was shown that the standards remain stable on the plate for 1 h after chromatogram development.