J. AOAC Int. 3, 708-713 (2018). HPTLC of acetylsalicylic acid (1), hydrochlorothiazide (2), enalapril (3), and atorvastatin (4) in a formulation on silica gel with n-hexane – ethyl acetate – methanol – water – acetic acid 42:40:15:2:1. Quantitative determination by absorbance measurement at 210 nm for (3) and 265 nm for (1), (2) and (4). The hRf values for (1) to (4) were 68, 44, 31 and 54, respectively. Linearity was in the range of 0.600-6.000 μg/zone for (1), 0.058-1.102 μg/zone for (2), 0.505-6.560 μg/zone for (3) and 0.100-1.000 μg/zone for (4). The intermediate precision was below 3 % (n=5). The LOD and LOQ were 0.311 and 0.942 μg/zone for (1), 0.043 and 0.130 μg/zone for (2), 0.331 and 1.003 μg/zone for (3) and 0.044 and 0.135 μg/zone for (4). (Note by the editor: Calibration should start at LOQ, not below.) Recovery was between 97.0 and 101.3 % for (1) to (4).

J. Liq. Chromatogr. Relat. Technol. 41, 645-657 (2018). Review of the most relevant TLC methods for the analysis of food and dietary supplements in the period of 2000-2018. General techniques for food analysis by TLC were described as well as selected applications for the analysis of butter fat, edible oil, flavorings, grains, honey, milk, soft drink and juice, spice, sweetener, vegetable, thickening agents, wine and other alcoholic beverages.

J. Chromatogr. Sci. 56, 518-523 (2018). Presentation of a validated method for the quantitation of dihydrokaempferol-4′-O-glucopyranoside. This flavanonol glucoside is a marker compound in the flower of Alcea rosea L. with significant antioxidant and anticancer activity against the HepG-2 cell line. HPTLC on silica gel with ethyl acetate – methanol – water – acetic acid 600:100:80:3 over 70 mm with chamber saturation for 30 min. Quantitative determination by absorbance measurement at 295 nm. The amount of dihydrokaempferol-4′-O-glucopyranoside in the flowers of A. rosea was 0.733 g/100 g and 0.928 g/100 g after maceration and sonication for 15 min, respectively. Linearity was in the concentration range of 0.9-3.6 µg/zone. The %RSD of the intra-day and inter-day precision was 0.2–1.5 % and 0.5–1.7 %, respectively. The LOD and LOQ were 312 ng/zone and 947 ng/zone, respectively.

J. Chromatogr. A 1569, 212-221 (2018). Presentation of a method for simultaneous determination of mono-, di-, oligo- and polysaccharides in food by HPTLC on silica gel with acetonitrile – water 4:1 containing 3.6 mM natural products reagent A in a single development. Use of the method for both, effective food screening and quantification for up to 20 samples in parallel on the same plate with good reproducibility of the separation at control of the layer activity, and with the determination coefficients of the calibration curves between 0.9980 and 0.9998. Test of the method with 4 different prebiotic food and 60 naturally degraded inulin samples proved its advantages of minimal sample preparation along with the determination of the intact inulin and FOS allowed the evaluation of the natural inulin degradation profile, as shown for naturally degraded inulin samples, and the method is robust and suitable for routine analysis, especially in food control, as well as might be of interest in other fields, e.g. plant breeding, edible insects, functional feed and metabolic processes.

Phytochem. Anal. 30, 121-131 (2019). HPTLC bioautography of essential oils of oregano, rosewood and cumin on silica gel with ethyl acetate – petroleum ether 1:19 for cumin, ethyl acetate – petroleum ether 1:9 for oregano and ethyl acetate – petroleum ether 1:3 for rosewood. 2D resolution by eluting for a second time along the orthogonal axis. TLC-direct bioautography by spraying with a bacterial suspension of methicillin‐sensitive S. aureus NCTC 1298 (MSSA), methicillin‐resistant S. aureus NCTC 12497 (MRSA), E. coli NCTC 8003, ciprofloxacin‐resistant E. coli (clinical isolate), P. aeruginosa NCTC 6749, P. aeruginosa (clinical isolate), vancomycin‐sensitive Enterococcus faecium and vancomycin‐resistant E. faecium NCTC 12202, followed by incubation at 37 ºC for 4 h. Antimicrobial fractions were further characterized by NMR spectroscopy, GC-MS and LC-MS.

J. Planar Chromatogr. 31, 469-476 (2018). HPTLC of metformin hydrochloride (1) and dapagliflozin (2) on silica gel with acetonitrile ‒ ammonium acetate 10% ‒ acetic acid 90:9:1. Quantitative determination by absorbance measurement at 228 nm. Linearity ranged between 1-10 μg/mL for (1) and 10-100 μg/mL for (2). LOD and LOQ were 314 and 950 ng/mL for (1) and 3.1 and 9.4 μg/mL for (2). The intermediate precision was <2 % (n=3). Average recovery was 99.9 % for (1) and 99.6 % for (2).

CBS 84, 4-7 (2000) HPTLC-AMD of raffinose, sucrose, 1+6-kestoses, neo-kestose, nystose, and fructosyl-nystose on diol layer with a 9-step gradient from acetonitrile/acetone 1:1 - water 85:15 to acetonitrile/acetone 1:1 - water 95:5. Detection by dipping in 4-aminobenzoic acid reagent, followed by heating at 115 °C for 15 min. Quantitative determination by fluorescence measurement at 366/>400 nm and absorbance measurement at 400 nm.

CBS 90, 14 (2003). HPTLC of waste water on silica gel with dichloromethane - methanol - ammonia 90:10:1.Quantitative determination by absorbance measurement at 270 nm.