J. Planar Chromatogr. 35, 273-279 (2022). HPTLC of sweetener saccharin (1), acesulfame-K (2), neohesperidin (3), aspartame (4), stevioside (5), rebaudioside A (6), sucralose (7), and Na-cyclamate (8) in food samples on silica gel with ethyl acetate - methanol - acetic acid 5:1:1. Detection by dipping into the following reagent sequece, followed each by plate heating and image documentation or densitometry: 1) Primuline reagent (100 mg primuline in 20 mL water and 80 mL acetone), followed by solvent evaporation and detection at 366 nm; 2) ninhydrin reagent (0.3 g ninhydrin dissolved in 95 mL isopropyl alcohol and 5 mL glacial acetic acid), followed by heating at 120 °C for 5 min and detection at white light; 3) 2-naphthol sulfuric acid reagent (1 g 2-naphthol dissolved in 90 mL ethanol and 6 mL 50 % sulfuric acid added dropwise), followed by heating at 120 °C for 5 min and detection at white light. Quantification by absorbance measurement at 200 nm for (1), 230 nm for (2), 290 nm for (3), 500 nm for (4) to (7) and 650 nm for (8).  Linearity was between 30 and 600 ng/zone for (5) and (6) and 800 and 1600 ng/zone for (8).   

J. Planar Chromatogr. 35, 153-159 (2022). HPTLC of glucuronic acid in gum samples of Sterculia urens on silica gel with 1-propanol - water 7:3. Detection by spraying with napthoresorcinol sulfuric acid reagent, followed by heating at 105 °C for 5 min. Quantitative determination by absorbance measurement at 580 nm. The hRF value for glucuronic acid was 43. Linearity was between 300 and 700 ng/zone. Interday and intra-day precisions were below 2 % (n=3). Recovery was between 100.4 and 102.3 %.

J Chromatogr A, 1640, 461929 (2021). Study of the impact of different strains, culture media and parameters (temperature, time, rotational speed, and glucide and amino-acid supply) on the metabolite profile of bacteria. Samples were cultivation broths of Bacillus subtilis, B. licheniformis, B. pumilus and B. amyloliquefaciens, as well as their respective supernatant liquid-liquid extracts (apolar solvents only or QuEChERS method with acetonitrile and MgSO4 – NaCl mixture 4:1). HPTLC on silica gel (normal phase and RP-18), either as bands (for small volumes of extracts) or as areas for supernatants and bigger volumes of extracts. Extract areas were focused with a three-step procedure (up to 20mm with acetone, and twice with methanol); unextracted supernatants were focused twice with methanol and once with tetrahydrofuran, but the application zone of the plate had to be cut before development, due to the high matrix load. Development with ethyl acetate – methanol – water at different ratios after activation of the plate surface with magnesium chloride (33% relative humidity), evaluation in white light and UV. Detection of antibacterial compounds with Aliivibrio fischeri bioassay. Derivatization with primuline (for lipophilic substances) and diphenylamine aniline sulfuric acid reagent (for saccharides). This method allowed a fast comparison: A) of the patterns of the different strains (presence /absence and intensity of detected or antibacterial bands); B) of cultivation parameters: the number of metabolites increased with time, rotational speed (oxygen level), and at 37°C (vs. 30°C), whereas a minimal medium allowed the detection of more metabolites, due to the lower matrix load; C) of the impact of the extraction parameters: choice of the solvents (QuEChERS method had no advantage here), solvent – supernatant ratio (1:3 showed richer patterns than 1:1); D) of the HPTLC parameters used (better separation and resolution with normal phase vs. RP18 layers).

Food Chem. 362, 130167 (2021). HPTLC of monosaccharides rhamnose, xylose, arabinose, mannose, glucose, galactose and sucrose in cladodes from Opuntia ficus-indica and Opuntia joconostle on silica gel with acetonitrile - 0.3 % ammonium hydroxide 17:3. Detection by dipping into thymol (0.2 %) and sulfuric acid (5 %) in methanol reagent, followed by heating at 95 °C for 2 min.

Planta Med. 85(2), 154-159 (2019). Two new cycloartane triterpene heterosides (cimiheraclein F and a shengmanol derivative) isolated from Actaea heracleifolia aerial parts (Ranunculaceae) were submitted to acid hydrolysis (HCl 0.4 M in methanol 60 %, 90°C, 2 h). The glycone moieties were purified and developed on TLC silica gel with ethyl acetate – chloroform – methanol – water 3:2:2:1. Detection after spraying with sulfuric acid 10 % in water and heating. The glycones were identified in both cases as L-arabinopyranose by comparison of the RF values (and of specific optical rotation) to a standard.

J. Planar Chromatogr. 33, 489-499 (2020). HPTLC of fructose (1), glucose (2) and sucrose (3) in honey on silica gel with 1-butanol-2-propanol - boric acid - water 3:5:1. Detection by spraying with 2 mL of aniline diphenylamine phosphoric acid reagent, followed by heating at 110 ºC for 10 min. The hRF values for (1) to (3) were 14, 32 and 27, respectively. Linearity was between 250 and 1250 ng/zone for (1) to (3). Intermediate precision was below 7 % (n=3). The LOD and LOQ were 22 and 67 ng for (1), 33 and 100 ng for (2) and 21 and 64 ng for (3), respectively. Average recovery was 100.7 % for (1), 101.4 % for (2) and 104.0 % for (3).

J. Planar Chromatogr. 32, 109-114 (2019). HPTLC of fructose (1), glucose (2), maltose (3), raffinose (4) and sucrose (5) in the roots of the seven Asparagus species A. adscendens, A. racemosus, A. retrofractus, A. officinalis, A. densiflorus, A. falcatus, and A. sprengeri on silica gel with propanol - ethyl acetate - water 6:3:1. Detection by spraying with a methanolic solution of diphenylamine, aniline, and ortho-phosphoric acid, followed by heating at 140 °C for 2-3 min. Quantitative determination by absorbance measurement at 600 nm. The hRF values for (1) to (5) were 55, 50, 31, 11 and 46, respectively. Linearity was between 100 and 500 ng for (1) to (5). The intermediate precision was below 2 % (n=3). The LOD and LOQ were 22 and 66 ng for (1), 13 and 40 ng for (2), 51 and 155 ng for (3), 13 and 39 ng for (4) and 76 and 229 ng for (5), respectively. Average recovery was 97.9 % for (1), 99.9 % for (2), 99.3 % for (3), 98.3 % for (4) and 97.8 % for (5).

J. Liq. Chromatogr. Relat. Technol. 34, 902-919 (2011). HPTLC of seven sugars (D-glucose, D-galactose, D-mannose, beta-D-fructose, alpha-D-fructose, sucrose, maltose, lactose) in food samples on silica gel with n-butanol - isopropanol - acetic acid - boric acid solution (200 mg boric acid in 10 mL water) 6:14:1:3. Detection by dipping into either aniline diphenylamine o-phosphoric acid reagent or p-aminobenzoic acid reagent. Quantitative determination by absorbance measurement at 370 nm. The HPTLC method was more sensitive by a factor of 8 for detection of sugars when compared to HPLC; only fructose showed a slightly better LOQ (difference by factor of 3). LOQ was better than 63 ng for HPTLC and about 500 ng for HPLC. Method comparison showed a good correlation and only a mean difference between both methods of 1.5 % sugar content for many food samples analyzed. HPTLC is a fully compliant method for determination of sugars in food. Application in the bioanalytical field was shown as well.