Chromatographia 67 (5-6), 441-447 (2008). HPTLC of forskolinon on silica gel aluminium foil with benzene - methanol 9:1. Quantitative determination by densitometry in the absorbance mode at 545 nm after spraying with anisaldehyde sulphuric acid reagent. The method was validated: linearity was between 100 and 1000 ng/spot (r = 0.994) and the limits of detection and quantification were 8 and 27 ng/spot respectively. Application of the proposed method for determination of forskolin in Coleus forskohlii root and in capsule dosage forms, which showed 0.18 and 0.57 % w/w of forskolin, which was subjected to acid and alkali hydrolysis, oxidation, photodegradation and heat degradation. The method shows good repeatability, selectivity and accuracy, and effectively separates forskolin from components of C. forskohlii root, from excipients of capsule as well as the degradation products of forskolin. It can be used for routine analysis and as a stability-indicating method.

Anal. Chim. Acta, 572 (2), 237-242 (2006). Presentation of a stability-indicating method for simultaneous determination of the steroidal hormones levonorgestrel and ethinyloestradiol both in bulk drug and in low-dosage oral contraceptives by HPTLC on silica gel with hexane - chloroform - methanol 4:12:1. The hRf value of levonorgestrel was 65 and of ethinyloestradiol 43. The compounds were well separated from their degradation products. Quantitative determination by absorbance measurement at 225 nm. Linearity of levonorgestrel and ethinyloestradiol was 200–800 and 40–160 ng/spot, respectively.

J. Chromatogr. Sci. 48 (2), 109-113 (2010). HPTLC of nebivolol hydrochloride on silica gel with toluene – methanol - triethylamine 19:6:1. The hRf value of nebivolol hydrochloride was 33. Quantification by densitometry in the absorbance mode at 281 nm. Linearity was between 500 and 3000 ng/spot with r2= 0.9994. The limit of detection and quantification was 63 and 191 ng/spot, respectively. Nebivolol hydrochloride was subjected to acid and alkali hydrolysis, oxidation, thermal degradation, and photodegradation. The degradation products were well-resolved from the main component.

J. of Beihua Univ. (Natural Sci.), 11 (5), 420-423 (2010). TLC on silica gel with 1) petroleum ether (60-90 ºC) - ethyl acetate 4:1 and 2) chloroform - propanone - n-hexane - acetic acid 80:40:2:5. Detection under UV 365 nm. Derivatization by spraying with 10 % vanillin in sulfuric acid and heating at 105 ºC until the zones were visualized. Identification by comparison with the standards of the components in the individual composition drug.

J. Ethnopharmacol. 137, 99-104 (2011). HPTLC of karanjin in rabbit plasma on silica gel with dichloromethane - toluene - methanol 35:15:3. Qualitative evaluation under UV 366 nm and quantitative determination by densitometry at 366 nm. Linearity was between 1.0 and 15.0 µg/mL. LOD and LOQ were 0.5 and 1.0 µg/mL, respectively. The inter-day and intra-day accuracies were 97.1 % and 92.2 %, respectively. Recovery (by standard addition) was between 98.2 % and 99.9 %.

J. of Chromatogr. Sci. 52 (1), 5-11 (2014). Presentation of a method for the simultaneous determination of diacerein in the presence of rhein, the active metabolite and hydrolytic degradation product of diacerein, and emodin, the diacerein impurity, in bulk powder and different pharmaceutical formulations. TLC on silica gel with hexane – ethyl acetate – acetic acid 75:50:1, detection and quantification by densitometry at 230 nm. The hRf values were 12, 44 and 60 for diacerein, rhein and emodin, respectively. The linearity ranges were 0.5–10 µg/band for diacerein and rhein, and 0.5–7 µg/band for emodin. Comparison with a HPLC method showed no significant differences.

J. Chromatogr. Sci. 56, 317-326 (2018). Development of an accurate, sensitive and highly selective stability-indicating method for simultaneous determination of agomelatine (AGM) and its forced degradation products (Deg I and II) by HPTLC on silica gel with chloroform – methanol – ammonia 90:10:1. Quantitative determination by densitometry at 230 nm over the concentration range of 0.2-1.2 μg/band for AGM in pure form and human plasma, and 0.1-1 μg/band for both Deg I and II. The method was successfully applied for the analysis of AGM in pharmaceutical formulations. Statistical comparison of the results to those obtained by HPLC revealed its high accuracy and good precision.

J. Chromatogr. 339, 163-169 (1985). TLC of nitrazepam and its main metabolites on silica with acetone - ethyl acetate - 28 % NH3 1:9:0.1. Quantification by direct UV densitometry. Detection limit 5-10 ng/ml.