J. Sep. Sci. 44, 530-538 (2021). HPTLC of tamsulosin (1) and tadalafil (2) in presence of their degradation products (2) and (3) on silica gel with ethyl acetate - toluene - methanol - ammonia 20:10:20:3. Quantitative determination by absorbance measurement at 280 nm. The hRF values for (1) to (4) were 55, 68, 14 and 24, respectively. Linearity was between 0.5 and 25 µg/zone for (1) and (2). Intermediate precision was below 2 % (n=3). Average recovery was 99.7 % for (1) and 100.3 % for (2).

J. Planar Chromatogr. 33, 647-661 (2020). HPTLC of empaglifozin (1) and linagliptin (2) on silica gel with chloroform - methanol - ammonia (25 %) 100:10:1. Quantitative determination by absorbance measurement at 225 nm. The hRF values for (1) and (2) were 31 and 71, respectively. Linearity was between 100 and 5000 ng/zone for (1) and 50 and 2500 ng/zone for (2), respectively. Intermediate precision was below 2 % (n=3). The LOD and LOQ were 32 and 97 ng/zone for (1) and 14 and 42 ng/zone for (2), respectively. Average recovery was 100.1 % for (1) and 99.9 % for (2). Comparison with a similar TLC method showed no significant statistical differences.

J. Planar Chromatogr. 33, 631-646 (2020). HPTLC of azilsartan medoxomil (1) and chlorthalidone (2) on silica gel with toluene - methanol - ethyl acetate - formic acid 35:10:5:1. Quantitative determination by absorbance measurement at 241 nm. The hRF values for (1) and (2) were 55 and 36. Linearity was between 800 and 4000 ng/zone for (1) and 250 and 1250 ng/zone for (2), respectively. Intermediate precision was below 2 % (n=3). The LOD and LOQ were 15 and 44 ng/zone for (1) and 10 and 32 ng/zone for (2). Recovery was between 100.8 and 101.7 % for (1) and 99.4 and 101.0 % for (2).

J. Planar Chromatogr. 33, 231-244 (2020). HPTLC of apremilast on silica gel with toluene - methanol - ethyl acetate 7:2:1. Quantitative determination by absorbance measurement at 241 nm. The hRF value for apremilast was 63. Linearity was between 200 and 1000 ng/zone. Inter-day and intra-day precision were below 1 % (n=3). The LOD and LOQ were 4 and 13 ng, respectively. Recovery rate was between 99.7 and 100.0 %. Apremilast was subjected to acidic, alkaline, oxidative, dry heat, neutral, and photolytic degradation conditions. The method was implemented using a quality risk management and quality by design approach for regulatory requirements.

J. Planar Chromatogr. 20, 365-371(2007). Estimation of retention data by use of correlation equations and physicochemical properties is a useful tool in liquid chromatography. HPTLC of an homologous series of 9 s-triazines on RP-18, cyano-, and amino phase in unsaturated chambers with aqueous solutions of the organic solvents acetonitrile, tetrahydrofuran, and dioxane. After development the dried plates were examined under UV light at 254 nm.

62nd Indian Pharmaceutical Congress Abstract No. F-301 (2010). TLC of brimonidine tartrate on silica gel with methanol – toluene – triethylamine 10:35:2. The hRf value was 48. Quantitative determination by absorbance measurement at 247 nm. The method was linear in the range of 100-600 ng/band. The sample was subjected to different stress conditions (acid, base, oxidative, thermal and photolytic). With the proposed method all the degradation products were well resolved from the drug.

Der Pharma Chemica 2(3), 8-18 (2010). HPTLC of berberine on silica gel with methanol – acetic acid – water 8:1:1. The band corresponding to berberine showed an hRf value of 74. Quantitative determination by absorbance measurement at 350 nm. The method was linear in the range of 100-500 ng/band. Different samples analysed by the proposed method were found to contain 11.8-12.5 mg/g berberine. The recovery was between 98.0-100.3 %.

J. Liq. Chromatogr. Relat. Technol. 38, 1499-1506 (2015). RP-HPTLC of piperazine in pharmaceutical formulations on RP-18 with acetonitrile - water 3:2 modified with 1.5 % tetrafluoroborate. Quantitative determination by absorbance measurement at 247 nm. The hRF value for piperazine was 43. Linearity was in the range of 0.8-2.2 μg/zone. LOD and LOQ were 0.11 and 0.34 μg/zone. The intermediate precision was below 3.5 % (n=3). Recovery was between 99 and 103 %. Significant changes and improvements regarding the hRF value were observed when tetrafluoroborate was added to the mobile phase.