J. AOAC Int. 102, 776-780 (2019). HPTLC of sibutramine, phenolphthalein, and three PDE5 inhibitors (sildenafil, vardenafil and tadalafil), as well as caffeine, fluoxetine, theophylline, and acetaminophen as adulterants in weight loss products on silica gel with methyl tert-butyl ether – toluene – methanol 8:2:1. Densitometric absorption measurement at 225 nm. The hR_F values of reference substances increased in the following order: fluoxetine, sildenafil, vardenafil, caffeine, theophylline, tadalafil, acetaminophen, phenolphthalein and sibutramine. The method was successfully used for the screening of 12 commercial products. Of those, nine products tested positive for at least one undeclared component.

J. Liq. Chromatogr. Relat. Technol. 42, 324-329 (2019). HPTLC of individual pharmaceutical products containing moxifloxacin HCl (1), ofloxacin (2), amoxicillin trihydrate (3), acetylsalicylic acid + acetaminophen + caffeine (4), nimesulide (5), irbesartan (6), and pantoprazole (7) on silica gel with methanol - ammonium hydroxide - water 7:2:1 for (1), methanol - ethyl acetate - ammonium hydroxide 7:7:3 for (2), acetone - water - methanol - glacial acetic acid 20:10:5:2 for (3), ethyl acetate - glacial acetic acid 19:1 for (4), toluene - acetone 10:1 for (5), ethyl acetate - acetone - glacial acetic acid 180:40:1 for (6) and ethyl acetate - methanol - toluene 4:1:2 for (7). Quantitative determination by absorbance measurement at 366 nm. The hRF values for (1) to (3) and (5) to (7) were 72, 30, 80, 33, 40 and 43, respectively. The hRF values for (4) were 62 for acetylsalicylic acid, 49 for acetaminophen and 22 for caffeine. The quantitative methods were used to transfer the Global Pharma Health Fund (GPHF) Minilab Manual and U.S. Food and Drug Administration (FDA) Compendium to HPTLC following a model process for moxfloxacin HCl, ofloxacin, and amoxicillin trihydrate. The results met the guidelines of the model process regarding the calibration curves: r-values were at least 0.99, assays were within 85–115% specification limits of the label values of individual tablets and capsules, validation recoveries were within 95 - 105 % at all three spike levels, RSDs were no higher than 3 % for assays and validation analyses, and peak identity and peak purity checks had correlation factors of at least
0.99. 
 

J. Liq. Chromatogr. Relat. Technol. 42, 238-248 (2019). Review of recent applications of TLC in medicinal chemistry, including the determination of lipophilicity of biologically active compounds and its influence as activity descriptors of absorption, distribution, metabolism, elimination and toxicity. Practical applications of TLC as a fast screening technique in different stages of monitoring processes were also described, including systems recently used for stability studies of selected drugs.

J. Planar Chromatogr. 32, 273-283 (2019). HPTLC of trimetazidine dihydrochloride (1) and its potential impurities, namely, piperazinecarboxaldehyde (2), trimethoxybenzyl alcohol (3), and trimethoxybenzaldehyde (4) on RP-18 with acetonitrile - methanol - 0.1 % aqueous ortho-phosphoric acid (pH 6.2) 9:9:2. Quantitative determination by absorbance measurement at 254 nm. The hRF values for (1) to (4) were 21, 35, 50 and 85, respectively. Linearity was between 0.05-10 µg/zone for (1), 0.05-1.1 µg/zone for (2), 0.05-1.2 µg/zone for (3) and 0.04-1.0 µg/zone for (4). The intermediate precision was below 2 % (n=9). The LOD and LOQ were 20 and 50 ng/zone for (1) to (3) and 15 and 40 ng/zone for (4), respectively. Recovery rate was 99.6 % for (1), 100.5 % for (2), 100.1 % for (3) and 99.4 % for (4).

J. Planar Chromatogr. 32, 317-321 (2019). HPTLC of 2-chloroaniline (1) at trace levels
in quetiapine fumarate (2) on silica gel with toluene and methanol 7:4. Quantitative determination by absorbance measurement at 235 nm. The hRF value of (1) was 85. Linearity was between 2.5-12.5 ng/zone for (1) and 400-2400 ng/zone for (2). The intermediate precision was below 2 % (n=3). The LOD and LOQ of (1) were 0.02 and 0.05 ng/zone for (1) [Editor´s note: This seems to be erroneous.] and 1.27 and 3.87 ng/zone for (2), respectively. Recovery rate ranged between 98 and 100 % for (1) and (2).

J. Planar Chromatogr. 32, 329-334 (2019). HPTLC of orlistat on silica gel with chloroform - methanol 49:1. Detection by spraying with anisaldehyde - sulfuric acid, followed by heating at 120 °C for 5 min. Quantitative determination by absorbance measurement at 600 nm. The hRF value of orlistat was 75. Linearity was between 600 and 4000 ng/zone. The intermediate precision was below 2 % (n=6). The LOD and LOQ for orlistat were 140 and 466 ng/zone, respectively. Recovery rate was between 97.7 and 104.5 %.

J. Planar Chromatogr. 32, 323-327 (2019). HPTLC of mirabegron (1) and solifenacin succinate (2) on silica gel with methanol - ethyl acetate - triethylamine 80:20:1. Quantitative determination by absorbance measurement at 222 nm. The hRF values for (1) and (2) were 76 and 56, respectively. Linearity was between 2.0-5.5 µg/zone for (1) and 0.4-1.1 µg/zone for (2). The intermediate precision was below 2 % (n=3). The LOD and LOQ were 34 and 103 ng/zone for (1) and 20 and 61 ng/zone for (2), respectively. Recovery rate was between 98.5 and 101.2 % for (1) and 99.2 and 100.8 % for (2).

J. Planar Chromatogr. 32, 295-307 (2019). HPTLC of empagliflozin (1) and metformin (2) with ammonium acetate - methanol - acetonitrile - ethyl acetate 6:2:9:3. Quantitative determination by absorbance measurement at 254 nm. The hRF values for (1) and (2) were 49 and 81, respectivley. Linearity was between 2 and 10 µg/zone for (1) and 1 and 5 µg/zone for (2). The intermediate precision was below 2 % (n=3). The LOD and LOQ were 3 and 11 ng/zone for (1) and 110 and 331 ng/zone for (2), respectively. Recovery rate was between 98.4 and 99.8 % for (1) and 99.0 and 99.6 % for (2).