J. Sep. Sci. 43, 2228-2239 (2020). HPTLC of binary mixtures of tenofivir disoprixil fumarate (1) / lamivudine (2) and lamivudine (2) / zidovudine (3) on silica gel with dichloromethane - acetonitrile - methanol - ammonia 67:20:10:3. Quantitative determination by absorbance measurement at 272 nm. The hR_F values for (1) to (3) were 43. 79 and 81, respectively. Linearity was in the range of 5-40 µg/mL for (1), 2-16 µg/mL for (2) and 1-16 µg/mL for (3). Intermediate precisions were below 2 % (n=3). The LOD and LOQ were 1 and 3 µg/mL for (1), 1 and 4 µg/mL for (2) and 2 and 6 µg/mL for (3), respectively. Recovery was between 96.5 and 101.8 % for (1) to (3).

J. Sep. Sci. 43, 2330-2337 (2020). HPTLC of metoclopramide (1), ergotamine (2), caffeine (3), and paracetamol (4) on silica gel with ethyl acetate - ethanol - ammonia 90:10:1. Quantitative determination by absorbance measurement at 272 nm. The hR_F values for (1) to (4) were 14, 36, 49 and 74, respectively. Linearity was in the range of 1-24 µg/zone for (1), 0.1-6.5 µg/zone for (2), 0.8-3.5 µg/zone for (3) and 0.8-10 µg/zone for (4), respectively. Intermediate precisions were below 2 % (n=9). The LOD and LOQ were 336 and 1017 ng/zone for (1), 43 and 130 ng/zone for (2), 265 and 802 ng/zone for (3) and 262 and 793 ng/zone for (4). Average recovery was 99.7 % for (1), 100.6 % for (2), 100.1 % for (3) and 100.2 % for (4).

Phytochem. Anal. 31, 57-67 (2019). HPTLC profiling of the leaves of Fraxinus excelsior on silica gel with ethyl acetate - water - formic acid 8:1:1. Qualitative identification under UV light at 254 and 366 nm. The hR_F value of chlorogenic acid was 90.

Planta Medica 84(9/10), 584-593 (2018). A review with 120 references on DESI technique coupled with MS for natural products. Paragraph on sample preparation (9 references) compares analyte desorption surfaces: either directly from the biological sample, or indirectly from surfaces on which the sample had been imprinted. Direct desorption can be performed only from samples with hard, smooth and regular surfaces, or from cryosections, which are usual for animal tissues. For plants, indirect analysis is preferable because of their wax-rich, hydrophobic, absorbent and/or irregular surfaces. Imprinting of plant organs and tissues can be performed either on glass (however with a very rapid ablation of the analytes from its surface), or on sorbent material, like TLC silica gel or porous polytetrafluoroethylene (PTFE). While PTFE layers are reported as more expensive and better in terms of reproducibility and quantitative analysis, both TLC and PTFE layers have similar performance for analyte retention until desorption.

Planta Medica 84(9/10), 710-715 (2018). The fractionation of an n-butanol extract of Cistanche phelypaea (Orobanchaceae) aerial parts through cyclodextran column chromatography with methanol was monitored on TLC silica gel with chloroform – methanol – water 70:30:3, detection by spraying with cerium sulfate reagent. In the 11 major fractions obtained, 4 new phenylethanoid glycosides were further identified, as well as brandioside (a phenylpropanoid glycoside), and heterosides of apigenin (flavonoid) and of pinoresinol (lignan).

Planta Medica 84(9/10), 716-720 (2018). The fractionations of n-hexane and chloroform extracts of Guarea guidonia aerial parts (Meliaceae) through silica gel column chromatography was monitored on TLC silica gel with cerium sulfate / sulfuric acid as derivatization reagent. In the fractions obtained, 3 new tirucallane-type triterpenoids (guareolide, guareoic acids A and B) were further identified, as well as other terpenoids (flindissone, acetyldihydronomilin, picroquassin E, boscartol C, and acneorubins A, B, and X).

Planta Medica 84(9/10), 729-735 (2018). The chloroform fraction of a methanolic extract of Euphorbia taurinensis whole plant (Euphorbiaceae) was submitted to a multi-step fractionation through column chromatography. Monitoring by TLC on silica gel (mobile phases see below) followed by derivatization with concentrated sulfuric acid and heating at 105°C. The fractions obtained were purified by repeated cycles of preparative TLC alone or alternating with preparative HPLC, leading to the isolation of segetane, ingenane, and jatrophane diterpenes. Depending on the subfractions, preparative TLC silica gel and reverse-phase C18 layers were used, with cyclohexane – ethyl acetate – ethanol 25:15:1 for normal phase, and with mixtures of acetonitrile (or methanol) and water for RP.

J. Planar Chromatogr. 33, 149-160 (2020). HPTLC of palonosetron on silica gel with methanol - ammonia 20:1. Quantitative determination by absorbance measurement at 254 nm. The hR_F value for palonosetron was 58. Linearity was between 0.1 and 2 µg/zone. Intermediate precisions were below 2 % (n=3). The LOD and LOQ were 0.02 and 0.06 µg/zone, respectively. Recovery rate was 99.5 %.