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 %.

J. Planar Chromatogr. 33, 119-129 (2020). HPTLC of levocetrizine hydrochloride (1) and montelukast sodium (2) on silica gel with ethyl acetate - methanol - triethylamine 125:125:1. Quantitative determination by absorbance measurement at 234 nm. The hR_F values for (1) and (2) were 23 and 55, respectively. Linearity was between 100 and 500 ng/zone for (1) and 200 and 1000 ng/zone for (2). Intermediate precisions were below 2 % (n=3). The LOD and LOQ were 9 and 28 ng/zone for (1) and 22 and 65 ng/zone for (2), respectively. Recovery rate was between 99.3 and 100.1 % for (1) and 100.0 and 100.3 % for (2).

J. Planar Chromatogr. 33, 79-87 (2020). HPTLC of vitamin C in the dried fruit of Rosa laxa on silica gel with ethyl acetate - absolute ethanol - water 40:24:15. Quantitative determination by absorbance measurement at 273 nm. The hR_F value for vitamin C was 61. Linearity was between 0.25 and 1.2 µg/zone. Intermediate precisions were below 2 % (n=6). Average recovery was 98.4 %.

J. Planar Chromatogr. 33, 109-118 (2020). HPTLC of empagliflozin (1), linagliptin (2) and metformin hydrochloride (3) on silica gel with n-butanol - water - glacial acetic acid 6:3:1. Quantitative determination by absorbance measurement at 223 nm. The hR_F values for (1) to (3) were 73, 52 and 33, respectively. Linearity was between 0.1-0.7 µg/zone for (1), 0.05-0.35 µg/zone for (2) and 10-70 µg/zone for (3). Intermediate precisions were below 2 % (n=3). The LOD and LOQ were 2 and 5 µg/zone for (1), 9 and 27 ng/zone for (2) and 19 and 59 ng/zone for (3), respectively. Recovery was between 99.4 and 100.7 % for (1), 99.3 and 100.5 % for (2) and 98.6 and 101.8 % for (3).