J. of Chromatogr. Sci. 58 (4), 303 - 308 (2020). Determination of dapoxetine hydrochloride (DAP) and tadalafil (TAD) in their binary mixtures either as raw materials or in pharmaceutical formulations, by HPTLC on silica gel with ethanol - ethyl acetate 1:9. Quantitative determination by densitometry at 222 nm. The linear range was 0.1 - 1.6 and 0.2 - 2.5 μg/band for dapoxetine and tadalafil, respectively, with accuracies of 98.9 % ± 0.6 and 99.3 6% ± 1.4, respectively.

J. of Modern Trad. Chinese Med. 20 (7), 821-824 (2018). Mulusin, a class of isoprene flavonoids extracted from Mori Cortex, has anti-tumor, anti-inflammatory, hypoglycemic, hypolipidemic, analgesic, anti-spasm, and cholinesterase restricting activity. For quality control, TLC of mulusin on silica gel with petroleum ether - dichloromethane - ethyl acetate 15:8:10 at 25 ± 0.3 ˚C with chamber saturation for 30 min. Detection at UV 254 nm. The hRF of mulusin standard was 43. Quantitative absorbtion measurement of morusin by densitometry at 273 nm. Linearity was in the range of 200 - 1100 ng/zone (r=0.999), precision on one plate was RSD = 1.21 % (n=6) and on plate-to-plate RSD = 2.30 % (n=6). Recovery from standard sample addition was 99.2 % (RSD = 1.51, n = 6). The LOD was 20 ng/zone and LOQ 40 ng/zone.

J. Chromatogr. Sci. 57 (5), 411-417 (2019). The high polarity of the has made it difficult to quantify the alkaloids. This study was designed to develop and validate a thin-layer chromatography (TLC) densitometric-based method using high-performance thin-layer chromatography for quantification of berberine. HPTLC of the protoberberine alkaloids in Coptis teeta rhizome on silica gel aluminium foil with butanol - ethyl acetate - formic acid - water 3:5:1:1. Quantitative determination by absorbance measurement at 351 nm. The hRf of berberine was 70. The linearity obtained graphically with a correlation coefficient of 0.997 was in the concentration range of 90-210 ng/band.LOD and LOQ were 30 and 70 ng/band, respectively. The berberine concentration in the methanol extract of C. teeta was 30.9 ± 0.6 mg in 100 mg of the crude drug. The method developed here in can be implemented in the analysis and routine quality control of herbal materials and formulations containing C. teeta and berberine.

J. Chromatogr. Sci. 57 (4), 312-322 (2019). Development of a method for simultaneous analysis of five antipsychotic and medicinally important β-carboline alkaloids (βCAs), namely, harmalol, harmaline, harmine, harmane and norharmane, by HPTLC on silica gel with chloroform - methanol - glacial acetic acid 39:11:1. Quantification by densitometry in fluorescence mode at 366 nm. The linearity range of standard βCAs was 25-250 ng/band, with r² between 0.97 and 0.99. The recovery was between 83.9 and 112.4 %, repeatability of the application 0.6-2.4 %, repeatability of measurement 1.9-3.1 % and intermediate precision 0.6-11.2 %). LOD and LOQ were 4.9-6.6 and 16.5-21.9 ng/band, respectively. The method proved to be simple, cost-effective, precise, sensitive and specific for the determination of βCAs in the herbs Fagonia schweinfurthii, Peganum harmala and Tribulus terrestris, and was useful in forensic and industrial analysis and fingerprinting of various βCAs containing herbs and drug formulations.

J. of Chromatogr. Sci. 57 (2), 149-155 (2019). Description of a selective stability indicating method for chromatographic separation of ascorbic acid (ASC), paracetamol (PAR) and guaifenesin (GUF) in presence of paracetamol toxic impurity [4-aminophenol (4-AP)] and guaifenesin related substance [impurity, (guaiacol) (GUC)] by HPTLC on silica gel with chloroform - acetone - trifluoroacetic acid 65:35:3, detection under UV 254 nm. Quantification by densitometry. The hRf values were 5 (ASC), 12 (4-AP), 24 (GUF), 41 (PAR), and 56 (GUC). The linearity was in the range of 0.4-2.4, 0.4-2.8 and 4-15 μg/band for ASC, PAR and GUF, respectively. Statistical comparison of the obtained results with those achieved by HPLC showed no significant difference. The HPTLC method proved to have advantages over HPLC, it was more sensitive and selective and permits its application in quality control of the drugs.

J. Chromatogr. A 1594, 181-189 (2019). Development of a simple and rapid procedure for the determination of quinalphos in human whole blood by HPTLC on silica gel with n-hexane – acetone 9:1 after extraction from spiked blood samples with the optimum solvent, diethyl ether, at pH 3 (average recovery = 93.6%), detection and quantification by densitometry at 325 nm in absorbance mode. Validation by examination of the effect of different organic solvents and pH on the extraction yield of quinalphos, and by investigation of the interference of other organophosphorus pesticides of forensic relevance (not observed). The linearity was in the range of 1 to 100 μg/mL with r2 = 0.9981, the sensitivity (LLOQ) at 1 μg/mL. The within-day precision and between-day precision ranged from 0.2 to 1.0%, and 0.1 to 0.8%, respectively, with an overall average recovery of 91.1% at three concentrations 1, 10, and 50 μg/mL. For different storage conditions for the samples no significant decrease in the concentration of quinalphos was observed. Application of developed procedure in three fatal cases of poisoning.

Planta Medica 84(6/7), 465-474 (2018). The new concept “Comprehensive HPTLC Fingerprinting” was applied to define specifications for the identification and purity assessment of Angelica gigas roots, and for the quantification of its markers: the coumarins decursin and decursinol angelate. Methanolic root extracts of A. gigas (10 reference materials, 24 commercial samples), of 26 other Apiaceae species (including 10 Angelica, 9 Ligusticum, 2 Notopterygium, 4 Peucedanum, and Levisticum officinale) and of mixtures, were developed with toluene - ethyl acetate - acetic acid 90:10:1 on HPTLC silica gel (at 33% relative humidity, chamber pre-saturated for 20 min with filter paper and developing solvent) and dried for 5 min. Detection under white and UV lights before and after derivatization by dipping into 10% sulfuric acid in methanol and then heating 3 min at 100°C. Quantitative evaluation by densitometry in fluorescence mode at UV 313 nm, and luminance was also calculated from the image pixels. The study showed the presence in A. gigas of nodakenin, decursinol, 7-demethylsuberosin, imperatorin, osthole, and isoimperatorin at hRF 0, 4, 15, 33, 38 and 44 respectively. Z-ligustilide (hRF 59) was absent from A. gigas, allowing 1) to distinguish it from several other Apiaceae species; 2) to identify in mixtures with A. gigas two common adulterants (A. acutiloba, A. sinensis) even at 1% in the root powder. Minimal content of A. gigas fingerprint markers (decursin + decursinol acetate, co-eluting at hRF 27) was assessed as 3% (w/w) based on the quantified peaks from A. gigas reference materials.

J. of Chromatogr. A 1568, 188-196 (2018). Mass spectra by DART-MS were recorded directly in situ the bioautogram, immediately after direct bioautography (DB). This allowed to detect bioactive analytes within the bioautogram and discriminate microorganism cells and polar bioassay medium ingredients which could otherwise stress the MS system. DB-DART-MS was used for bioactive compounds in cosmetics using the Bacillus subtilis and Aliivibrio fischeri bioassays for detection of Gram-positive and Gram-negative antimicrobials. Planar yeast estrogen screen was used for detection of estrogen-effective compounds. HPTLC-DART-MS of parabens in hand creams either on silica gel with petroleum ether - glacial acetic acid 20:3 or on RP-18W with methanol - water 1:1. Detection under UV 254 and 366 nm. Bioassay by immersing the neutralized chromatograms into the bacterial suspensions.