J. of Chromatogr. Sci. 58 (8), 737-746 (2020). Presentation of a method for determination of the antimicrobial capability of the metabolite coriloxin, derived from mycoendophytic Xylaria sp. NBRTSB-20, and purified by column chromatography with its purity assessed by HPLC, UPLC-ESI-QTOF-MS, FT-IR and NMR. Determination of the antimicrobial capability by TLC–bioautography with the agar overlay technique. Evaluation under visible light. The LOD of coriloxin antimicrobial activity was 10 μg for Escherichia coli and 20 μg for Staphylococcus aureus and Fusarium oxysporum. Inter- and intra-day precision was below 6.6 %. The recovery was between 91.2 to 108.7 % with RSD values of 0.9-2.3 %.

Phytochem. Anal. 31, 711-721 (2020). HPTLC of 13 aporphine and four benzylisoquinoline-type alkaloids in the twigs of Ocotea spixiana on silica gel with propanol - water - ammonium hydroxide 18:2:1. Detection by desorption electrospray ionisation mass spectrometry (DESI-MS).

J. Planar Chromatogr. 33, 523-530 (2020). HPTLC of clonazepam (1), lorazepam (2), alprazolam (3), diazepam (4), furazepam (5), oxazepam (6) and nitrazepam (7) in urine on silica gel with chloroform - glacial acetic acid 9:1. Direct extraction of the substances from the plate into a mass spectrometer. The hRF values for (1) to (7) were 73, 44, 22, 64, 18, 53 and 40, respectively. Linearity was between 0.2 and 0.8 µg/mL. Intermediate precision was below 5 %. LOD was 1 ng/mL for each substance. Average recovery was 67.1 % for (1), 68.9 % for (2), 64.2 % for (3), 73.1 % for (4), 50.7 % for (5), 81.4 % for (6) and 64.4 % for (7).

J. Planar Chromatogr. 33, 397-404 (2020). HPTLC of ephedrine on silica gel with n-butyl acetate - acetone - 1-butanol - 5 M ammonia - methanol 4:2:2:1:1. Detection at UV 254 nm. The separated zones eluted directly from the plate into an MS. The ionization mode was selected as electrospray ionization (ESI). The hRF value for ephedrine was 41.

J. Liq. Chromatogr. Relat. Technol. 43, 344-350 (2020). HPTLC of hydrodistilled Plectranthus amboinicus essential oil on silica gel with n-hexane - ethyl acetate - ethanol 95:3:2. Detection by dipping into anisaldehyde sulfuric acid reagent, followed by heating at 100 ºC for 5 min. HPTLC-bioprofiling was performed using the following assays by dipping the chromatogram into the respective solution, followed by drying, incubation and documentation at white light or measuring bioluminescence: DPPH* radical reagent assay (using a 0.2 mg/mL 2,2-diphenyl-1-picrylhydrazyl solution in methanol), AChE inhibitory assay, tyrosinase inhibitory assay, alpha- and beta-glucosidase inhibitory assays, alpha-amylase inhibitory assay, Gram-negative antimicrobial bioassay (chromatogram immersion into a A. fischeri suspension), and Gram-positive antimicrobial bioassay (chromatogram immersion into a B. subtilis bacterial suspension). Direct analysis in real time mass spectrometry allowed the detection of five bioactive compounds: caryophyllene oxide (hR_F 20), a-humulene (hR_F 26), carvacrol (hR_F 40), methyl carvacrol ether (hR_F 76) and caryophyllene (hR_F 84).

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.

Food Control. 103, 111-118 (2019). Thin layer chromatography in tandem with surface-enhanced Raman scattering (TLC-SERS) of histamine in tuna samples on diatomaceous earth plates with ethanol - ammonia 3:1. Detection by spraying with Pauly's reagent (equal mixture of 20 mM sulfanilic acid in a 1 M HCl solution and 200 mM sodium nitrite solution, followed by adding 10 % anhydrous sodium carbonate in a 5 % ethanol solution). Gold nanoparticles were deposited on the plate zone and measurements were performed using a Raman spectrometer with an excitation laser wavelength of 785 nm.

J. of Chromatogr. A 1568, 188-196 (2018). Mass spectra by DART-MS were recorded directly in situ the bioautogram, immediately after direct bioautography (DB). This allowed to detect bioactive analytes within the bioautogram and discriminate microorganism cells and polar bioassay medium ingredients which could otherwise stress the MS system. DB-DART-MS was used for bioactive compounds in cosmetics using the Bacillus subtilis and Aliivibrio fischeri bioassays for detection of Gram-positive and Gram-negative antimicrobials. Planar yeast estrogen screen was used for detection of estrogen-effective compounds. HPTLC-DART-MS of parabens in hand creams either on silica gel with petroleum ether - glacial acetic acid 20:3 or on RP-18W with methanol - water 1:1. Detection under UV 254 and 366 nm. Bioassay by immersing the neutralized chromatograms into the bacterial suspensions.