Chinese J. Food & Drug 23 (3), 229-232 (2021). Non-benzodiazepines are inhibitors directly acting in the central nervous system, with sedative, anxiolytic and anticonvulsant effects. They are used as third generation sedative-hypnotic drugs to treat insomnia. However, it has been found that they are illegally added to some health foods on the market, which may cause long-term abuse and cause harm to the human body. Therefore, it is necessary to strenghten a rapid screening to detect the illegal addition of non-benzodiazepines to health foods, to improve the efficiency of supervision, and to crack down illegal practices.  TLC of ethyl acetate extracts of health foods adulterated with non-benzodiazepines, on silica gel with dichloromethane - methanol - ethyl acetate 17:2:6. Detection in UV 254 nm, identification by fingerprint comparison with the standards zolpidem, zalepron and zoppilon. Using this method, 65 batches of health food samples obtained from the market were screened, and four of them were suspected of illegal addition of zopiclone. This result is consistent with the analysis using both HPLC-DAD and HPLC-MS, and proved the  TLC method to be simple, fast, accurate, easy to operate, and well suitable for quick screening.

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.

Anal. Bioanal. Chem. 411, 6655-6665 (2019). HPTLC of lovastatin present in lactone (1) and hydroxy acid forms (2) and mycotoxin citrinin (3) in red yeast rice on silica gel with n-hexane - acetone - 10 % acetic acid 60:40:1. Quantitative determination by absorbance measurement at 238 nm for (1) and (2) and fluorescence measurement at 313/> 400 nm for (3). The hRF values for (1) to (3) were 35, 23 and 7, respectively. Linearity was between 50 and 500 ng/zone for (1) and (2) and 5 and 50 ng/zone for (3). Intermediate precision was below 2 % (n=5). The LOD and LOQ were 10 and 50 ng/zone for (1) and (2) and 1 and 4 ng/zone for (3). Average recovery was 109.9 % for (1) to (3).

Anal. Bioanal. Chem. 411, 725-734 (2019). HPTLC of bisphenol A (1) and its nine brominated analogs, namely monobromobisphenol A (2), 2,2’-dibromobisphenol A (3), tribromobisphenol A (4), tetrabromobisphenol A (TBBPA) (5), TBBPA mono(methyl ether) (6), TBBPA mono(allyl ether) (7), TBBPA mono(2,3-dibromopropylether) (8), TBBPA bis(allyl ether) (9), TBBPA bis(2,3-dibromopropyl ether) (10) in chicken samples on silica gel with n-hexane - ethyl acetate - dichloromethane - acetic acid 25:5:5:1. Detection at UV 254 nm. Further analysis by high-performance liquid chromatography-diode array detector/triple quadrupole mass spectrometry. The hRF values for (1) to (10) were 30, 32, 33, 45, 58, 68, 69, 69, 91 and 86, respectively.  

J. Planar Chromatogr. 32, 343-346 (2019). HPTLC of tetrahydrocannabinol (1), cannabidiol (2) and cannabinol (3) on silica gel with n-hexane - diethyl ether 4:1. Quantitative determination by absorbance measurement at 206 nm. The hRF values for (1) to (3) were 48, 56 and 41, respectively. Linearity was between 0.5 and 9.5 µg/zone for (1) to (3). The intermediate precision was below 6 % (n=6). The LOD and LOQ were 710 and 2370 ng/zone for (1), 290 and 980 ng/zone for (2) and 380 and 1280 ng/zone for (3), respectively. Recovery rate was 97.8 % for (1), 93.5 % for (2) and 107.2 % for (3).

J. Planar Chromatogr. 29, 394-396 (2016). HPTLC of 1-(8-bromobenzo[1,2-b;4,5-b′]difuran-4-yl)-2-aminopropane, popularly known as Bromo-DragonFLY on silica gel with methanol – ammonia 200:3. Quantitative determination by absorbance measurement at 281 nm. The hRF value for Bromo-DragonFLY was 50. Linearity was between 6 and 75 μg/zone. The intermediate precisions were below 4.3 % (n=3). The LOD and LOQ were 2.1 and 6.3 μg/zone, respectively. Average recovery was 94.5 %.

Detection and identification of phenethylamines (stimulants and hallucinogenes). Sci. Pharm. 55, 1-11 (1987). Method for the rapid identification of phenethylamine. Color reactions with 4 reagents: a) formaldehyde - sulfuric acid (Marquis), b) ammoniummetavanadate - sulfuric acid (Mandelins), c) ammoniummolybdate - sulfuric acid (Fröhde), d) nitric / sulfuric acid as preliminary group identification preceding TLC. TLC with 6 separation systems, 4 using silica, 2 RP-18 layers, with 6 solvent systems. Postchromatographic derivatization with 5 systems selected according to layer material and previous observations. Results of the identification procedure presented in the form of tables.

J. Chinese Herb Med. (Zhongcaoyao) 23, 125-126 (1992). TLC of six bufoginins on silica with chloroform – acetone – cyclohexane 3:3:4. Quantification by densitometry at 300 nm.