E-Journal of Chemistry 7(2), 341-348 (2010). HPTLC of nebivolol hydrochloride and hydrochlorothiazide on silica gel with ethyl acetate - methanol - 25 % ammonia 17:2:1 with chamber saturation. The hRf value of hydrochlorothiazide was 21 and of nebivolol 41. Densitometric evaluation at 285 nm. The method was linear in the range of 200-1000 ng/band for nebivolol and 500-2500 ng/band for hydrochlorothiazide. The recovery was 98.9-102.4 %. Comparison of the HPTLC method with a RP-HPLC method and a UV spectroscopic method gave comparable results. The HPTLC method is suitable for routine quality control.

Journal of Pharmacy Research 3(2), 332-334 (2010). HPTLC on silica gel with methylene chloride - methanol - ammonia 17:2:1. The hRf value of amlodipine was 19 and of nebivolol 41. Densitometric evaluation at 285 nm. The method was linear in the range of 100-500 ng/band for both compounds. The average recovery was 99.9-102.1 for both compounds and there was no interference with additives present in tablet dosage forms.

Indian J. Pharma. Educ. Res. 44(4), 341-344 (2010). HPTLC of silica gel with toluene - ethyl acetate - methanol - formic acid 5:16:21. The hRf value was 51. Densitometric evaluation at 220 nm. The method was linear in the range of 300-1800 ng/band. The sample was subjected to different stress conditions (acid, base, oxidative, thermal, and photolytic). Degradation products were well separated from trandolapril, therefore the method can be used for stability studies.

J. of Chromatogr. A 1218 (19), 2648-2660 (2011). Review on the kinetic performance of stabilized particle layers, particle membranes, and thin films for TLC. Forced flow and pressurized planar electrochromatography is best suited to overcome the limited performance achieved by capillary flow for stabilized particle layers. For conventional and high performance plates band broadening is dominated by molecular diffusion at low mobile phase velocities typical of capillary flow systems and by mass transfer with a significant contribution from flow anisotropy at higher flow rates typical of forced flow systems. There are few possible changes to the structure of stabilized particle layers that would significantly improve their performance for capillary flow systems while for forced flow a number of avenues for further study. New media for ultra TLC shows possibilities for miniaturized high performance systems but the realization of their true performance requires improvements in instrumentation for sample application and detection.

J. of Chromatogr. A 1218 (19), 2668-2675 (2011). Use of the changes in emission of berberine cation, induced by non-covalent interactions with lipids on silica gel for detection and quantification of lipids using fluorescence densitometry in HPTLC/AMD. Three different HPTLC/AMD gradients were developed for the separation of 1) neutral lipid families and steryl glycosides, 2) different sphingolipids, and 3) sphingosine–sphinganine mixtures. Rationalization of fluorescent molar responses of studied lipids, and differences in response among different lipid families in the light of a previously proposed model of FDIC response, which is based on ion-induced dipole interactions between the fluorophore and the analyte, likewise, application of computational calculations using molecular mechanics as a complementary useful tool to explain high FDIC responses of cholesteryl and steryl-derivatives, and moderate responses of sphingolipids. Proposal of an explanation for the high FDIC response of cholesterol, whose limit of detection is 5 ng.

J. Pharm. Biomed. Anal. 54, 422-425 (2011). HPTLC of aloin in several aloe dried extracts and related commercial formulations on silica gel with ethyl formate – methanol – water 200:29:20. Evaluation under 254 nm. Detection by immersion in 10 % H3BO3 in methanol, followed by heating at 110 °C for 10 min. Quantitative determination by fluorescence measurement at 365/K540 nm.

Phytochem. Anal. 22, 367-373 (2011). HPTLC of thymoquinone in the seeds of Nigella sativa on silica gel with toluene – cyclohexane 4:1. Quantitative determination by absorbance measurement at 254 nm. The hRf of thymoquinone was 28. The linearity range was 100-1400 ng/zone. The limit of detection and limit of quantification was 50 and 150 ng/spot, respectively. Inter- and intraday precisions were 1.6 and 2.4 % (n=6), respectively. Recovery (by standard addition) was 100.1 %. The method is reproducible and selective for the analysis of thymoquinone with added advantages of low cost of reagents, speed and minimal sample preparation, satisfactory precision and accuracy.

J. Sep. Sci. 34, 2397-2404 (2011). TLC of polyaromatic hydrocarbons (PAH) to examine the influence of magnetic field on the retention of compounds on silica gel, with monocomponent mobile phases containing n-hexane, n-heptane, n-octane, benzene, and toluene and as binary phases, mixtures of n-hexane - benzene 9:1, 7:3, and 1:1. The magnetic field influences the retention and separation efficiency of investigated chromatographic systems.