J. Liq. Chromatogr. Relat. Technol. 34, 805-816 (2011). HPTLC of methyl (1), ethyl (2), propyl (3), and butylparaben (4) on RP-18 first with methanol 60 % and in a second development with methanol 30 %. Quantitative determination by absorbance measurement at 254 nm. The hRf values of parabens (1) - (4) were 57, 47, 37 and 28, respectively. Linearity was between 0.46-2.74 µg/band for (1), 0.50-2.99 µg/band for (2), 0.54-3.24 µg/band for (3) and 0.58-3.49 µg/band for (4). The LOD and LOQ were between 100-370 ng/zone and 200-440 ng/zone, respectively. Relative standard deviation of precision was below 3.5 %. Recovery (by standard addition) was higher than 96.3 % in all cases.

J. Planar Chromatogr. 24, 82-87 (2011). TLC of crude extracts and madecassoside, asiaticoside, madecassic acid, and asiatic acid on silica gel with concentration zone with chloroform - glacial acetic acid - methanol - water 15:8:3:2; the hRf value was 45, 55, 94, and 97, respectively. Detection by spraying with anisaldehyde-sulfuric acid reagent, followed by heating at 95 °C for 10 min or until the colored zones appeared. The correlation coefficients were between 0.9904 and 0.9982 and linearity was in the range of 1.25-10 nmol, corresponding to approximately 0.5-5 µg/zone for the acids and 1.2-10 µg/zone for the glycosides. The LOD and LOQ was 300 and 720 ng/zone for the sapogenin and saponin, respectively, and 500 and 1200 ng/zone. The average precision was less than 4 % for standards and between 4-6 % for samples.

J. Planar Chromatogr. 24, 66-71 (2011). HPTLC of extracts of Stresroak premix and gallic acid (1), mangiferin (2), and withanolide A (3) as standards on silica gel with A) ethyl acetate - formic acid - acetic acid - water 100:11:11:27, for (1) and (2), and B) chloroform - methanol 9:1 for (2) in a twin trough chamber. Quantitative determination by absorbance measurement at 280 nm for (1), 330 nm for (2), and 225 nm for (3). The hRf values of (1), (2) and (3) were 76, 29, and 48, respectively. The average recoveries were 100.4 % (1), 99.3 % (2) and 98.0 % (3). The linear concentration range was 50-150 ppm for (1), and 40-100 ppm for (2) and (3). The LOD, defined as the amount of compound required to produce a signal at least three times the noise level, for gallic acid, mangiferin, and withanolide A was 80, 110, and 200 ng for (1), (2), and (3), respectively. The LOQ was 20, 27, and 38 µg, 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.

International Journal of PharmTech Research 2(2), 1427-1430 (2010). Ashokarista formulations contain ashoka (Saraca indica) as the main ingredient. Its markers are catechin, (+)catechole, and (-)epicatechin. TLC of extracts and (+)catechin on silica gel with toluene - ethyl acetate - formic acid - methanol 15:15:4:0.1. Quantitative determination by densitometry in absorbance mode at 278 nm. For identification of the stem-bark of Saraca indica the fingerprint is evaluated after detection with anisaldehyde-sulphuric acid. The hRf value of (+)catechin was 54.

J. AOAC Int. 93, 820-824 (2010). HPTLC of mexiletine hydrochloride on RP-18 with tetrahydrofuran - citrate buffer (pH 4.45) 3:7 and on amino phase with chloroform - tetrahydrofuran - hexane - ethylamine 30:20:50:1. Quantitative determination by absorbance measurement at 217 nm. Linearity was between 0.5 and 8.0 µg/spot. The accuracy was 99.6 % for the amino phase and 99.5 % for the RP-18 phase. The %RSD of intra-day and inter-day precision was 1.2 and 2.7 %, respectively; for both layers LOD and LOQ were 100 and 300 ng/zone, respectively.

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.