Heliyon 6(8), e04654 (2020). HPTLC of ethanolic extracts of three algae (100µg/band) on silica gel, along with carotenoid standards (10µg/band), developed with toluene – acetone 7:3. Detection under white light. Carotenoids appeared orange or yellow, chlorophylls green, pheophytins dark khaki. Carotenoid patterns of the algae were very different depending on the family: red alga Eucheuma denticulatum (Solieriaceae) contained mainly zeaxanthin and lutein (hRF 44) and β-carotene (hRF 88), but also β-cryptoxanthin (hRF 69-71) and fucoxanthin (hRF 39); brown alga Sargassum polycystum (Sargassaceae) contained mainly fucoxanthin, and also cryptoxanthin; green alga Caulerpa lentillifera (Caulerpaceae) contained mainly zeaxanthin, but also astaxanthin (hRF 61) and canthaxanthin (hRF 77) in smaller amounts. Separately, HPLC-MS was used to confirm and quantify these compounds, which was necessary for carotenoids with similar hRF values: zeaxanthin and lutein (hRF 44), and β-carotene and lycopene (hRF 88).

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.

Chim. Acta 67, 334-351 (1984). Zur Kenntnis des Faktors F 430 aus methanogenen Bakterien: Struktrur des proteinfreien Faktors. (Factor F 430 from methanogenic bacteria: structure of the protein-free factor). HPTLC and PLC of highly complex nickel-containing porphinoids on silica with ethyl acetate - acetic acid - water 5:2:2, butanol - acetic acid - water 4:1:1 and trifluoro ethanol - acetic acid - water 4:1:1. Extraction from cells of methanobacterium thermoautokrophicum using numerous PLC steps. HPTLC allows the separation of isomeric porphinoids.

J. Planar Chromatogr. 4, 319-322 (1991). TLC of 15 aromatic amines on silica, alumina and cellulose with numerous solvents in different compositions. 0.1% aqueous solutions of sodium chloride or hydrochloric acid are considered as excellent eluents for achieving selective separation of diphenylamine or carbazole from indole. Detection i.a. by spraying with 1% ethanolic solution of dimethylaminobenzaldehyde containing 15-20 mL conc. sulfuric acid.

J. Planar Chromatogr. 17, 233-237 (2004). TLC of biogenic amines (dopamine, adrenaline, noradrenaline, 3-methoxytyramine, methanephrine, normethanephrine, vanillylmandelic acid, homovanillic acid, 3,4-dihdroxyphenylacetic acid, 3,4-dihydroxyphenylethyleneglycol, 3-methoxy-4-hydroxyphenylethyleneglycol) and methylxanthines (1-methylxanthine, 7-methylxanthine, theophylline, paraxanthine, theobromine, caffeine) on silica gel with mobile phases comprising a non-polar or weakly polar diluent (chloroform, heptane, or hexane) and a polar modifier (tetrahydrofurane, dioxane, acetone, or ethyl acetate). Examination under UV light or detection with a solution of iron(III) chloride (5 g) and iodine (2 g) in 50 mL of 20 % aqueous tartaric acid. Relationship between Rf values and mobile phase composition was investigated.

The Rf values of 6 compounds were given. The procedure is suitable for the separation of aminophenyl porphyrins which are similar in structure and nature.