Research J. Pharm. and Tech. 3(4), 1275-1278 (2010). A stability indicating HPTLC method has been developed for ofloxacin. The results were confirmed by bioautography. HPTLC on silica gel with n-butanol - ethanol - 25 % ammonia 5:5:4. The hRf value was 53. Densitometric evaluation at 299 nm. The method was linear in the range of 500-2500 ng/band. The sample was subjected to forced degradation (acid, base, oxidation, thermal, photolytic) and both degraded and un-degraded sample were analyzed by HPTLC and bioautography. The result obtained by bioautography confirmed that the antimicrobial activity of ofloxacin was directly related to its degree of degradation under different stress conditions. Further no inhibition zone was observed at another hRf than that of ofloxacin, which indicates that degradation products do not exhibit antibacterial activity. Bioautography studies were carried out in petri plates (10 cm diameter) using as media Mueller Hinton agar and as organism Escherichia coli NCIM 2066.

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 %.

62nd Indian Pharmaceutical Congress Abstract No. F-330 (2010). TLC of ofloxacin and ornidazole on silica gel with 1,4-dioxane – ethyl acetate – toluene – glacial acetic acid – water 5:5:3:2:2. The hRf values were 16 and 89 for ofloxacin and ornidazole, respectively. Quantitative determination by absorbance measurement at 287 nm. The results by TLC were comparable to the results by a spectophotometric method.

J. Planar Chromatogr. 24, 172-175 (2011). HPTLC of arjunolic acid on silica gel, prewashed with methanol, with chloroform - toluene - ethanol 4:4:1 in a twin-trough chamber saturated with mobile phase for 15 min. Detection by spraying with anisaldehyde reagent followed by heating at 110 °C for 5-7 min. Quantitative determination by densitometry at 600 nm. Linearity was between 50 and 500 ng/band. The hRf value was 28. The inter-day, intra-day, and inter-analyst precision was (%RSD, n = 6) 0.2-0.5, 0.3-0.4, 0.2-0.9 %, respectively. The recovery was in the range of 98.1-101.8 %. The robustness (%RSD, n = 3) was 0.2-2.1 %. LOD and LOQ were 18 and 50 ng/band, respectively.

J. Liq. Chromatogr. Relat. Technol. 37, 941-950 (2014). HPTLC of ibuprofen (1) and famotidine (2) on silica gel with methanol - ethyl acetate - hexane - ammonia 4:12:2:1. Quantitative determination by absorbance measurement at 264 nm. The hRf values for (1) and (2) were 41 and 69, respectively. Linearity was in the range of 320-9600 ng/zone for (1) and 10-300 ng/zone for (2). LOD and LOQ were 104 and 316 µg/mL for (1) and 3 and 10 µg/mL for (2). Recoveries (by standard addition) were in the range of 100-101 % for both (1) and (2). Intermediate intra- and inter-day precision was below 2 % (n=3).

Chromatographia 18, 512-516 (1984). Test of the retention behaviour of some substituted benzoic acids on reversed-phase TLC plates in the presence of ammonium bromide and various tetraalkylammonium compounds with different alkyl chain lengths. Description of the dependence of the Rf values of the test materials on the alkyl chain length of the ion-pair reagent and on the type of the inorganic counter ion. Ion-pair TLC, theory.

Part II. Thin-layer chromatographic studies. Analyst III. 707-710 (1986). Examination of o-phthalaldehyde-sulfuric acid as a fluorogenic spray reagent for TLC determination of some indol-3-yl acids. Investigation of the effects of 2-mercaptoethanol or cysteine, UV irradiation and gaseous electrical discharge. o-phthalaldehyde-sulfuric acid associated with an UV pre-irradiation was the best for the compounds examined. o-phthalaldehyde, fluorogenic reagent, indol-3-yl acids

J. Chromatogr. 368, 168-173 (1986). TLC of 2,6-dihydroxybenzoic, salicylic, 2,4-dihydroxybenzoic and gentesic acids on silica, or paraffin-coated silica, or octadecyl-bonded silica. With methanol - water based solvent systems, and on silica coated with 1, 12-bis(trimethyl ammonium)dodecane, or 1,3-bis(trimethyl ammonium)propane, or tetra-n-butylammonium, with methanol - dichloromethane based solvent systems. Comparison of the performance of the two bolaform ion-pair reagents with those of two conventional reagents.