J. Planar Chromatogr. 32, 309-316 (2019). HPTLC of vildagliptin (1) and metformin (2) in the presence of the toxic metformin impurity melamine (3) on silica gel with methanol - chloroform - formic acid 70:30:3. Quantitative determination by absorbance measurement at 215 nm. The hRF values for (1) to (3) were 78, 18 and 46, respectivley. Linearity ranged 0.2-2.6 µg/zone for (1), 0.4-4.5 µg/zone for (2) and 0.05-1.4 µg/zone for (3). The intermediate precision was below 2 % (n=3). The LOD and LOQ were 53 and 161 ng/mL for (1), 81 and 246 ng/mL for (2) and 15 and 48 ng/mL for (3), respectively. Recovery rate was 100.9 % for (1), 101.5 % for (2) and 99.2 % for (3). The results were compared statistically to the results obtained by a reported RP-HPLC method.

Indian J. Pharm. Sci. 69(4), 589 (2007). HPTLC of ropinirole on silica gel with methanol - acetone 4:1. Aripiprazole was used as internal standard. Under chromatographic conditions both ropinirole and aripiprazole were well separated. Evaluation under UV 254 nm. UV spectrometry was carried out at 250 nm.

CBS 100, 13-15 (2008). HPTLC of caffeine on silica gel with ethyl acetate - methanol - 25 % ammonia 90:15:1 (for samples of energy drinks) or chloroform - ethanol - 37 % acidic acid - acetone - water 54:27:10:2:2 (for samples of headache tablets). Detection under UV 254 nm. Quantitative determination by absorbance measurement at UV 274 nm. Automated online extraction with an HPTLC/MS interface connected to a ESI mass spectrometer. Without any internal standard the caffeine mass signal was recorded in the selected ion monitoring mode at m/z 195 [M+H]+. The method was validated. Repeatability was 5.6 % (%RSD, n=6) and reproducibility of the plate mean value was 1.5 % (%RSD, n=3).

J. Pharm. Biomed. Anal. 18, 271-274 (1998). HPTLC of cephalexin on silica gel (prewashed with the mobile phase) with ethyl acetate - acetic acid - water 7:2:1. Quantitative determination by absorbance measurement at 263 nm. The method was linear in the range of 200-1600 ng/spot, average recovery was 101 %. The analytical results obtained by HPTLC were comparable with the HPLC method of USP XXIII. The HPTLC method was suggested as alternative to the USP method considering the high throughput.

J. Chromatogr. A 1217(8), 1396-1398 (2010). Sparation of enantiomers of atenolol, propranolol, and salbutamol using different loading/impregnation techniques for the Cu(II) complexes of l-proline, l-phenylalanine, l-histidine, N,N-dimethyl-l-phenylalanine, and l-tryptophan. TLC on silica gel with acetonitrile – methanol – 2 mM aqueous solution of Cu(II) 3:4:5. The different techniques were: A) using the Cu(II)-l-amino acid complex as chiral mobile phase additive, B) development of plates in solutions of Cu-complex, and C) with a solution of Cu(II)acetate as mobile phase additive for plates impregnated with the amino acids. Detection of zones by exposure to iodine vapor.

International Seminar on Herbal Drug Research, PN-024 (2009). HPTLC of catechins and epicatechin in leaves of tea (Camellia sinensis on silica gel with toluene - ethyl acetate - formic acid 7:5:1. Quantitative determination by absorbance measurement at 254 nm. The leaves were found to contain 10-24 % of total polyphenols.

Phytochem. Anal. 22, 36-41 (2011). TLC of kutkoside (1) and picroside-I (2) in the kutki extract (Picrorhiza kurroa) on silica gel with ethyl acetate - methanol - glacial acetic acid - formic acid 25:5:1:1. Quantitative determination by absorbance measurement at 265 nm.The hRf of (1) was 42 and of (2) 61. The precision was 0.77 % and 1.01 % for (1) and (2), respectively. Linearity was between 80-480 ng/zone for both substances. Detection and quantification limits were 24 and 79 ng/zone for both. The intra-day and inter-day precisions were 0.4 % and 0.3 % (n=3) respectively. The recovery for (1) was 96.5 % and for (2) 96.0 %, respectively. The results were comparable with those obtained by HPLC.

Rapid Commun. Mass Spectrom. 25, 2201-2208 (2011). HPTLC of an equimolar mixture of malto-oligosaccharides, derivatized with p-aminobenzoic acid, on silica gel with acetonitrile – water – acetic acid 8:2:1. Quantitative determination by fluorescence measurement at 366 nm. The relative molar composition of the oligomers, determined by HPTLC, was used as a reference data for mass spectrometric analyses. For both electrospray ionization and matrix-assisted laser desorption/ionization methods, the instrumental parameters significantly influence the signal intensities and areas.