International Journal of Pharmaceutical Sciences Review and Research 2(2), 35-39 (2010). TLC on silica gel with methanol - chloroform 1:6. The hRf value was 38 and 68 for ramipril and telmisartan respectively. Densitometric evaluation at 210 nm. The method was linear in the range of 300-3000 ng/band and 500-4000 ng/band for ramipril and telmisartan respectively. The recovery was 98-102 %. The sample was subjected to different stress conditions (acid, base, oxidative, heat, photolytic) and all the degradation products were well separated from drug.

J Young Pharm 1(3), 259-263 (2009). A validated HPTLC method is described for simultaneous estimation of amlodipine besylate and telmisartan in dosage form. HPTLC on silica gel with tetrahydrofuran - dichloroethane - methanol - 25 % ammonia solution 60:20:10:4. The hRf value of amlodipine besylate was 45 and of telmisartan 22. Densitometric evaluation at 326 nm. Linearity was in the range of 1200-7200 ng/band for telmisartan and 400-1400 ng/band for amlodipine besylate. The limit of detection was 149 ng/zone and 53 ng/zone for telmisartan and amlodipine besylate, respectively. The limit of quantification was 453 ng/zone for telmisartan and 161 ng/zone for amlodipine besylate. The recovery was between 100.4 and 100.8 %.

Research Journal of Pharmaceutical, Biological and Chemical Sciences 1(4), 152-157 (2010). TLC on silica gel with methanol - 10 mM ammonium acetate 3:2 . The hRf value of ranolazine was 49. Densitometric evaluation at 271 nm. The method was linear in the range of 1-6 µg/band with a mean recovery of 100.0 %.

International Journal of Green Pharmacy 3 (1), 47-17 (2009). HPTLC of caffeine on silica gel with ethyl acetate - methanol 9:1. Densitometric quantification at 274 nm. The method was linear in the range of 2-14 µg/band. The sample extracted with 5 % diethyl amine in water gave the maximum yield of caffeine (2.1 %). The proposed chromatography gave the best resolution with caffeine at an hRf value of 40. The method can be used for quality control of tea samples in respect of caffeine contents.

J. Liq. Chromatogr. Relat. Technol. 33, 948-956 (2010). HPTLC of triazine herbicides (atraton, terbumelon, simazine, and terbutylazine) on silica gel with methyl-t-butyl ether - cyclohexane 1:1 in a vertical developing chamber without chamber saturation. Detection by derivatization using chlorine and starch-iodine. Quantitation with a CCD camera; the range of linearity covers two magnitudes (for atrazine from 10 ng to 1000 ng).

J. Planar Chromatogr. 23, 286-288 (2010). TLC of taxol with a stationary-phase gradient whereby parts of different TLC plates were connected by use of a MIGAS device. Separated taxol-containing zones were developed with methanol over 1 cm and thus moved to another plate. The lipophilic substance zone was cut out after separation of the sample on a silica gel plate with n-heptane - ethyl acetate 1:1. Further separation of taxol from accompanying hydrophilic substances was carried out on HPTLC RP-18W with methanol - water 4:1. The taxol-containing fraction was finally separated on silica gel with chloroform - acetone 3:1 in a horizontal chamber at constant temperature (30 +/- 1°C) and humidity (35 +/- 1 %). Detection under UV 254 and 366 nm. Quantitative determination by densitometry at 220 nm. The precision (n = 7) was 0.63 % and the repeatability (n = 7) 3.35 %. The limit of detection and quantification was 0.50 and 1.00 µg/zone, respectively; the correlation coefficient from linear regression was >0.98, and the linear calibration range was 1 - 10 µg/zone.

Talanta, 80 (5), 2007-2015 (2010). Presentation of a method for determination of oxybutynin hydrochloride (OX) in presence of its degradation product and additives in its pharmaceutical formulations. UV spectrophotometry using the first derivative of ratio spectra and measurment at 216 nm. Chemometric analysis using principal component regression and partial least-squares. HPTLC of OX and its degradation products methylparaben and propylparaben on silica gel with chloroform - methanol - ammonia - triethylamine 500:15:2.5:1. Quantitative determination by densitometry at 220 nm. Comparison of the results obtained with all three methods showed no significant differences.

Acta Chromatographica 21(1), (2009). Introduction of a new objective chromatographic response function RK, based on the kernel density estimation, for evaluation of the fingerprinting performance of a particular TLC system (uniformity of retention) for which a large set of experimental hRf values of possible components of the mixture is available. The RK criterion is insensitive to large numbers (hundreds or thousands) of hRf values, can be applied to one and two-dimensional TLC and is easily computed.