J. Agric. Food. Chem. 70, 10886-10898 (2022). HPTLC of 81 veterinary drugs from 6 different groups (glucocorticoids, anthelmintics, antiparasitics, coccidiostats, nonsteroidal anti-inflammatory drugs, and antibiotics) in 4 different matrices (honey, pig muscle, cow milk, and chicken eggs) on silica gel with acetonitrile - ammonia - ethanol 13:4:3 up to 80 mm and then in the reverse direction with methanol - acetonitrile - ethanol - ammonia 6:2:1:1 up to 45 mm. After each step, the plates were automatically dried in a cold stream of air for 3 min. Detection under UV light at 254 nm and fluorescence light detection (FLD) at 366 nm. Zones were eluted from the plate using a fully automated auto TLC-LC-MS interface for further analysis by high-resolution tandem mass spectrometry. Most veterinary drugs except penicillins and cephalosporins were detected at the 5 μg/kg level in pig muscle, cow milk, and chicken eggs and 25 μg/kg level in honey.

Anal. Bioanal. Chem. doi.org/10.1007/s00216-023-04656-0 (2023). HPTLC of nine convenience tomato products and a freshly prepared tomato soup on silica gel with n-hexane - dichloromethane - methanol - water 40:50:10:1. Detection under white light, UV light at 254 nm, and fluorescence light detection (FLD) at 366 nm. Effect-directed analysis (EDA) with the A. fischeri bioassay as well as α-/β-glucosidase and AChE/BChE enzyme inhibition assays. Metabolism (intestinal digestion of each sample) was simulated and integrated on the same adsorbent surface to study changes in the compound profiles. Further analysis by RP‑HPLC–DAD–HESI‑HRMS/MS using a TLC-MS interface. The method resulted in a 10-dimensional hyphenation including on-surface digestion (1D), planar chromatographic separation (2D), visualization using white light (3D), UV light (4D), fluorescence light (5D), effect-directed assay analysis (6D), heart-cut zone elution to an orthogonal reversed phase column chromatography including online desalting (7D) with subsequent diode array detection (8D), high-resolution mass spectrometry (9D), and fragmentation (10D), for screening of bioactive compounds and their intestinal conversion.

Anal. Bioanal. Chem. https://doi.org/10.1007/s00216-023-04605-x (2023). HPTLC of 60 pesticides in six plant protection products (PPP, namely Dithane, Dynali, Folpan, Switch, Teldor and Vivando) and three different food sample types (tomato, grape and wine) on RP-18 with n-hexane - toluene - ethyl acetate 4:1:1 for PPP, n-hexane - ethyl acetate 5:1 for the white wine extract, and n-hexane - toluene - ethyl acetate 5:1:1 for the grape and tomato extracts. Planar Yeast Estrogen Screening (pYES) by dipping into a citrate phosphate buffer (citric acid 6 g/L, disodium hydrogen phosphate 10 g/L, adjusted to pH 12 with sodium hydroxide), followed by drying in cold air stream for 4 min. The plate was immersed into the yeast cell suspension, followed by incubation at 30 °C for 3 h. Detection by dipping into a MUG solution (16 mg MUG in 1 mL dimethyl sulfoxide and 39 mL citrate phosphate buffer), followed by incubation at 37 °C for 1 h. Detection at FLD 366 nm and at FLD 366 nm/ > 400 nm. 

J Chromatogr A 1653, 462442 (2021). Samples were peptides obtained through tryptic hydrolysis of the 5 most abundant milk proteins: α-lactalbumin (α-LA), β-lactoglobulin (β-LG), α-, β- and κ-casein (CA). As standards, synthetic whey and pea (Pisum sativum, Fabaceae) peptides (selected based on the in silico tryptic digest of α-LA, β-LG, legumin A, and vicilin with one or zero miscleavages) were only used in the last assay for prediction of the RF values of peptides with known amino-acid (AA) sequences. Two-dimensional HPTLC on silica gel (pre-washed with methanol and activated 10 min at 100°), first with basic mobile phase sec-butanol – pyridine – ammonia – water 39:34:10:26, and (after 12h drying) in the orthogonal direction with acidic mobile phase sec-butanol – pyridine – acetic acid – water 11:8:2:5. Derivatization for peptides and proteins by immersion into fluorescamine (0.05 % in acetone); visualization under UV 254 nm and 365 nm. Computer-assisted determination of the x- and y-coordinates of the derivatized zones. Repeatability (n=8) of the 2D-HPTLC was statistically tested with the Kolmogorov-Smirnov test for normal distribution and with Dixon’s Q test for outliers. Relative standard deviation (RSD) for the RF values was 12.9 % for the first dimension (y-coordinates) and 16.5 % for the second dimension (x-coordinates). According to their higher intensity and sharpness, 15 – 20 detected zones from each protein hydrolyzate were selected, manually scraped from the derivatized layer, dissolved in formic acid solution (0.1 % in acetonitrile – water 3:2), mixed with an equal volume of matrix (dihydroxybenzoic acid 2 % in acetonitrile – water 3:7), crystallized on air on a ground steel target, before being desorbed by the laser beam of the MALDI-TOF-MS/MS (matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry). Direct hyphenation of HPTLC to MS was not performed, to avoid zone diffusion during plate coating with the matrix and to circumvent the stronger binding of polar peptides on the layer.  The MS spectra were acquired in positive reflector mode in m/z range 340 – 4000 (10 – 2500 for fragments), using an external peptide as calibration standard. Identification of 51 from the 85 selected peptides according to AA sequences was performed, using software programs allowing m/z calculation of protein fragments and estimation of cleavage sites. Correlation of the retention behaviour of the peptides with their properties (molecular weight MW, isoelectric point IEP, charges, polarity) was tested with Student’s two-sided t-test after calculation of Pearson’s correlation coefficients. The correlation was significant with IEP, percentages of anionic AA and of non-polar AA; but not with the following properties: MW, percentages of cationic AA and of uncharged polar AA. Finally, based on the correlation results, regression formulas were found to calculate the x- and y-coordinates of any known peptide from the percentage of non-polar AA (or vice-versa). The prediction power of these formulas was verified by repeating the complete 2D-HPTLC-MS experiment with the standard peptides of whey and of peas, and measuring the absolute and relative deviations between the actual x- and y-coordinates and the predicted values. The absolute deviations were higher in the lower RF zones. The average, relative RF value deviations (range 22.1 – 25.7 %) were not different between whey and pea peptides.

J. Food. Biochem. 45, e13764 (2021). HPTLC of L-arabinose, D-fructose, D-fucose, D-galactose, D-glucose, D-mannose, D-rhamnose, D-xylose in the roots of Sechium edule on silica gel with chloroform - n-butanol - methanol - water - acetic acid 9:15:10:3:3. Detection by spraying with 5 % sulfuric acid in methanol containing 0.1 % orcinol, followed by heating at 80 °C for 5-10 min.

J. Food. Biochem. 45, e13608 (2022). HPTLC of kaempferol-3-O-β-D-glucoside in florets of Brassica oleracea on silica gel with toluene: acetone: formic acid 15:5:1. Quantitative determination by absorbance measurement at 240 nm. The hRF value for kaempferol-3-O-β-D-glucoside was 40.

J. Food. Biochem. 46, e13855 (2022). HPTLC of Amomum subulatum dry fruits on silica gel with toluene - ethyl acetate - methanol - formic acid 14:6:2:1. Qualitative identification under UV light at 254 and 366 nm. 

Front. Pharmacol. 13, 925298 (2022). HPTLC of milk thistle on silica gel with toluene - ethyl formate - formic acid 8:10:1. Detection by dipping in NP reagent and subsequently in PEG reagent, followed by heating at 100 °C for 5 min. Qualitative analysis under UV light at 254 and 366 nm. HPTLC of alkylamides in coneflower on silica gel with ethyl acetate - ethyl methyl ketone - water - formic acid 5:3:1. Detection by dipping in NP reagent and subsequently in PEG reagent, followed by heating at 100 °C for 5 min. Qualitative analysis under UV light at 254 and 366 nm. HPTLC of black cohosh on silica gel with toluene - ethyl formate - formic acid 5:3:2. Detection by dipping into sulfuric acid reagent (20 mL of sulfuric acid in 180 mL of methanol), followed by heating at 100 °C for 5 min.