J. Pharm. Biomed. Anal. 53, 911-918 (2010). Comparative study on several approaches of TLC lipophilicity determination with the goal of standardization: single TLC runs, extrapolation of retention, principal component analysis of a retention matrix, PARAFAC on a three-way array and a PLS regression. All techniques were applied to 35 simple model solutes (e.g. benzoic acid, caffeine, benzocaine, isoniazide) using nine concentrations of six modifiers (acetonitrile, acetone, dioxane, propan-2-ol, methanol and tetrahydrofurane). Methanol and dioxane were most suitable as modifiers, while acetonitrile provided no suitable correlation of retention with lipophilicity. The approach of single TLC runs provided surprisingly good results. The chemometric processing methods (PCA, PARAFAC and PLS) did not show any advantage compared to classical methods. There is a need to use robust regression and correlation measures due to presence of significant outliers.

J. Planar Chromatogr. 24, 227-231 (2011). TLC of diethylamino hydroxybenzoyl hexyl benzoate (DHHB) and octyl methoxycinnamate (OMC) on silica gel with cyclohexane - diethyl ether - acetone 15:1:2 with chamber saturation for 20 min. Quantitative determination by densitometry in absorbance mode at 300 nm (for OMC) and 360 nm (for DHHB). Linearity was between 200 and 2000 ng/zone both for DHHB and OMC. LOD and LOQ was 50 and 472 ng/zone for DHHB and 50 and 488 ng/zone for OMC. The hRf value was 30 for DHHB and 47 for OMC. Recovery of DHHB was between 97.8-101.9 % and of OMC between 98.8-102.7 %

J. AOAC Int. 93, 783-786 (2010). HPTLC of etoricoxib (ETO) and thiocolchicoside (THIO) on silica gel (prewashed with methanol) with ethyl acetate - methanol 4:1 in a twin-trough chamber after preconditioning for 20 min. Quantitative determination by absorbance measurement at 290 nm. The calibration curve was linear over a range of 50-250 and 100-500 ng/band with correlation coefficients of 0.9948 and 0.9958 for ETO and THIO, respectively. LOD and LOQ were 11 and 33 ng/band for ETO and 25 and 76 ng/band for THIO. %RSD values were found to be 0.5 and 0.8 % for ETO and THIO for intra-day variations, while inter-day variations were 1.2 and 1.0 %, respectively. The recovery for ETO was between 100.2-101.1 % and for THIO 98.7-100.4 %.

J. Liq. Chromatogr. Relat. Technol. 35, 1459-1480 (2012). HPTLC of itraconazole on silica gel with toluene - ethyl acetate 1:5 + 1 drop ammonia. Quantitative determination by absorbance measurement at 266 nm. The hRf value of itraconazole was 77 and selectivity regarding matrix was given. Linearity was in the range of 50-2000 ng/zone. The intra-day and inter-day accuracy were in the range of 81.9-97.8 and 89.2-97.1 %, respectively. The limits of detection and quantification were 14 and 43 ng/zone, respectively. Recovery (by standard addition) was between 99.6 and 100.2 %.

J. Liq. Chromatogr. Relat. Technol. 36, 1528-1539 (2013). HPTLC of mebeverine hydrochloride (1), metronidazole benzoate (2), diloxanide furoate (3) and metronidazole (4) in pharmaceutical suspensions on silica gel with hexane - acetone - triethylamine 35:15:3. Quantitative determination by absorbance measurement at 254 nm. The hRf values of compounds (1) to (4) were 10, 34, 49 and 64, respectively. Linearity was 0.4-2.4 µg/zone for (1), 0.3-2.0 µg/zone for (2) and 0.4-2.4 µg/zone for both (3) and (4). Intermediate precision was below 1.2 %. Recovery (by standard addition) was 99.9-100.1 % for compounds (1) to (4). Comparable results were obtained when compared with reported RP-HPLC methods.

J. Liq. Chromatogr. Relat. Technol. 36, 2422-2430 (2013). HPTLC of glimepiride (1) and its main degradation impurities, glimepiride-sulfonamide (2), and glimepiride-carbamate (3) in pharmaceuticals on silica gel with toluene - ethyl acetate - methanol 8:5:1. Quantitative determination by absorbance measurement at 230 nm. The migration distances of (1), (2) and (3) were 48, 43 and 35 mm, respectively. LOD for the impurities (2) and (3) were found to be 2.2 and 2.3 ng/zone, respectively. LOQ values for the impurities (1) and (2) were 7.2 and 7.7 ng/zone. Intermediate precision was below 4.2 % (n=6). Recovery (by standard addition) was in the range of 94.9-102.3 % for (1) to (3).

J. Planar Chromatogr. 28, 67-73 (2015). HPTLC of (1) rifampicin, (2) isoniazid and (3) piperine on silica gel with toluene – methanol – chloroform 7:3:3. Quantitative determination by absorbance measurement at 300 nm. The hRF values of (1) to (3) were 51, 24 and 81, respectively. Linearities were between 100 and 700 ng/zone for (1) and (2) and between 20 and 90 ng/zone for (3). The intermediate intra-day and inter-day precisions for (1) to (3) were below 2 % (n=6). The LOD and LOQ were 12 and 33 ng/zone for (1), 20 and 53 ng/zone for (2) and 5 and 10 ng/zone for (3). Recoveries for (1) to (3) were in the range of 99-101 %.

J. Planar Chromatogr. 28, 362-372 (2015). HPTLC of niacin (1), atorvastatin (2), bezafibrate (3) and ezetimibe (4) or simvastatin (5) in plasma on silica gel with benzene - acetonitrile - n-butanol 7:2:1 + 1.5 % glacial acetic acid. Quantitative determination by absorbance measurement at 242 nm. The hRF values for (1) to (5) were 17, 38, 51, 65 and 66, respectively. Linearity was in the range of 15-650 ng/zone. LOD and LOQ were in the range of 5-50 and 15-150 ng/zone, respectively. The intermediate precision was below 5 % (n=3). Recovery ranged from 95 to 104 %.