J. Planar Chromatogr. 35, 331-337 (2022). HPTLC of selected varieties of hop cultivars H. lupulus on silica gel with 8 % isopropanol in dichloromethane. Detection under UV light at 254 and 366 nm. Direct bioautography by dipping into Bacillus subtilis bacterial suspension for 10 s, followed by incubation at 37 °C for 17 h. TLC plates were covered with 0.2 % aqueous MTT tetrazolium dye solution (thiazolyl blue tetrazolium bromide, 98 %), followed by incubation at 37 °C for 30 min. 
 

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 Chromatogr Sci, 60 (4), 364-371 (2022). Borage oil, extracted from Borago officinalis Linn., is a well-known medicinal compound with various benefits. Development of an affordable, simple, reliable, rapid and easily accessible method for the estimation of gamma-linolenic acid (GLA) in borage oil by HPTLC on silica gel with hexane - toluene - glacial acetic acid 3:7:1. The hRf value of GLA was 53 ± 4. Quantiative determination by densitometry at 200 nm with an LOD and LOQ of 221 and 737 ng/band, respectively. The method was validated by investigation for parameters like linearity, accuracy, specificity and precision, and found to be highly sensitive for the estimation of GLA in the herbal oil samples and formulations.

J. Strait Pharm. 33 (1), 63-66 (2021). Xiaoer Yanbian Keli granule is a TCM drug for clearing heat and detoxification, reducing phlegm, benefiting the pharynx, and relieving pain, and is mainly used for the treatment of sore throat and cough. For quality control, TLC of methanol extracts of the drug for (A) Lonicera japonica Thunb., on polyacetamide layer with acetic acid, detection in UV 366 nm, identification by fingerprint comparison; for (B) Belamcanda chinensis (L.) Redouté, TLC on silica gel with dichloromethane - butanone - methanol 3:1:1, detection in UV 254 nm, identification by fingerprint comparison; for (C) Radix Tinosporae, Eustoma grandiflorum (Raf.) Shinners and Scrophularia ningpoensis Hemsl., TLC of samples and standards palmatine chloride, harpagoside and platycodin D, on silica gel with n-butanol - glacial acetic acid - water 7:1:2, detection (1) in UV 366 nm, (2) by spraying with 2 % vanillin sulfuric acid solution and viewing in daylight, (3) by spraying with 2 % vanillin sulfuric acid solution, followed by heating at 105°C and viewing in daylight, identification by fingerprint comparison. The presented method was specific and well repeatable, and reduced the sample amount, simplified the sample processing steps, improved the detection efficiency, and reduced the detection costs.

J. Chromatogr. Sci. 60 (3), 267-273 (2022). HPTLC for the selective detection of the diuretic drug triamterene in pure form, tablets and human plasma, on silica gel with ethyl acetate - dimethylformamide - ammonia 70:27:3. Quantitative determination by fluorescence measurement at 440 nm improved the method sensitivity 250-fold compared with previously reported studies, and enabled the detection of triamterene in the linear concentration range of 0.8 to 60 ng/band for the pure drug and 1.0 to 60 ng/band for biological samples (human plasma).

Chinese J Oil Refining & Chem. Ind. 32 (6), 70-72 (2021). The output of coal tar accounts for about 3-4 % of the coal quantity in the furnace, which mainly contains benzene, toluene, xylene, naphthalene, anthracene and other components, and can be refined into phenolic oil, anthracene oil, asphalt and other products. These are widely used in dyes, medicine, spices, pesticides and other industries. Presentation of a method by using rod chromatography (rod TLC) / FID under optimized experimental conditions: TLC of 0.04 g/mL coal tar on activated chrombars under constant humidity conditions were developed in turn (A) with heptane to 11 cm, (B) with toluene to 6.5 cm and (C) with dichloromethane to 4.0 cm. The chrombars were scanned by FID and the content of saturated hydrocarbons, aromatic hydrocarbons, glia and bitumen was calculated by referring to the correction factors used in the determination of the four components in decompression slag oil. The method has been applied to four batches of coal tar samples or coal tar intermediate products produced by different process with satisfactory results, and proved to be simple, fast, economically feasible and suitable for coal chemical enterprises to quickly detect the change of coal tar composition, and to provide data reference for adjusting the device process parameters.

Molecules 25 (17), E3928 (2020). Samples were curcumin (as standard) and methanolic extracts of Curcuma xanthorrhiza and C. aeruginosa (Zingiberaceae) rhizomes, both separately and in mixtures. Separation on TLC silica gel with chloroform – methanol – formic acid 94:3:3. Densitometry of curcumin (hRF 50) in absorption mode at UV 427 nm. This method was validated with curcumin standard for selectivity (vs. demethoxycurcumin hRF 32), linearity range (250 - 450 ng), LOD (21 ng) and LOQ (69 ng), accuracy and precision. Curcumin contents were between 0.74 and 1.23 % in pure C. xanthorrhiza extracts, but decreased when adulterated with C. aeruginosa.

ALTEX - Alternatives to animal experimentation, 38(3), 387-397 (2021). Samples were standards of food contact contaminants with genotoxicity (4-nitroquinoline-1-oxide (NQO), aflatoxin B1, hexachloroethane, nitroso-ethylurea, phenformin, PhIP) or negative controls (alosetron, mannitol), and extracts of coated tin cans (extracted with n-hexane – acetone at 25°C for 16 h or by heating at 60 °C with ethanol 95 % for 240 h). HPTLC on RP18W layer, pretreated to harden the binder by heating 1 h at 120 °C, prewashed with methanol and with ethyl acetate and dried 4 min in cold air stream after each development. Application areas were focused to their upper edges by a two-fold elution with ethyl acetate, followed by 1 min drying in cold air stream. Development with toluene – ethyl acetate 8:5, followed by 5 min drying, neutralization with citrate buffer (pH 12) and 4 min drying. Effect-directed analysis for genotoxicity (SOS response – UMU-C test, using NQO as positive control) by immersion (speed 3.5 cm/s, time 3 s) into Salmonella typhimurium suspension and, after 3 h incubation at 37 °C and 4 min drying in cold air stream, into one of two fluorogenic substrate solutions (methylumbelliferyl- vs. resorufin-galactopyranoside). After 1 h incubation at 37 °C, visualization of mutagenic compounds as (blue vs. red) fluorescent zones at FLD 366 nm, and densitometry performed with mercury lamp for fluorescence (at  366 / >400nm vs. 550 / >580 nm, respectively). Further validation experiments, including spiking extracts with NQO, were performed showing good mean reproducibility, no quenching or other matrix effects. Lowest effective concentration of NQO was 0.53 nM (20 pg/band), 176 times lower than in the corresponding microtiter plate assays.