J. Planar Chromatogr. 29, 366-371 (2016). HPTLC of the diastereomeric amides of (RS)-etodolac on silica gel with acetonitrile – methanol – dichloromethane – water 12:2:2:1. Detection by exposure to iodine vapor. The hRf value for the first and second eluting diastereomers were 22 and 56, respectively.

J. Planar Chromatogr. 30, 271-274 (2017). HPTLC of the synthetic pyrethroids cypermethrin, deltamethrin, and λ-cyhalothrin on silica gel with n-hexane – acetone 4:1. Detection by spraying with freshly prepared hydralazine solution (37.5 mg in 50 mL 2N sodium hydroxide solution). The hRF value for α-cyano ester pyrethroids was 57.

J. Planar Chromatogr. 30, 245-250 (2017). 2D-HPTLC of allocryptopine (1), berberine (2), boldine (3), chelidonine (4), papaverine (5), emetine (6), columbamine (7), magnoflorine (8), palmatine (9), and coptisine (10) on Multi-K CS5 plates with methanol – water 4:1 containing 0.05 M diethylamine in the first dimension and methanol – ethyl methyl ketone (the latter contains 1 % 1-butyl-3-methylimidazolium tetrafluoroborate) 3:1 in the second dimension. Qualitative determination at UV 254 nm.

J. Chromatogr. A 1446, 141-148 (2016). Investigation of stationary phase gradients for chelation TLC as a tool to separate a mixture of metal ions. Preparation of the gradient stationary phases using controlled rate infusion from precursors containing mono-, bi-, and tri-dentate ligands, specifically 3-aminopropyltriethoxysilane, N-[3-(trimethoxysilyl)propyl] ethylenediamine, and N-[3-(trimethoxysilyl)propyl] diethylenetriamine. Confirmation of the presence and the extent of gradient formation using N1s X-ray photoelectron spectroscopy. The results showed that the degree of modification was dependent on the aminosilane precursor, its concentration, and the rate of infusion. Comparison of the separation of four transition and heavy metals (Co2+, Pb2+, Cu2+, and Fe3+) by TLC on gradient and uniformly modified plates with a mobile phase containing a stronger chelating agent, ethylenediaminetetraacetic acid. Manipulation of the retention of the metal ions by varying the surface concentration of the chelating ligands. The order of retention on unmodified plates and on plates modified with a monodentate ligand was Fe3+>Cu2+∼Pb2+∼Co2+, while the order of retention on plates modified with bi- and tri-dentate ligands was Fe3+>Cu2+>Pb2+∼Co2+. Fe3+ and Cu2+ were more sensitive to the concentration of chelating ligand on the surface and showed lower hRf values with increasing ligand concentration than Pb2+ and Co2+. Complete separation was achieved using a high concentration of the tridentate ligand coupled with a longer time for modification, giving a retention order of Fe3+ > Cu2+ > Co2+ > Pb2+.

J. Chromatogr. A 1526, 151-156 (2017). Development of a rapid and cost-effective method for determining brominated flame retardants (BFR) such as tetrabromobisphenol A/S (TBBPA/S) and their derivatives in soils, including TBBPA, TBBPA bis(allyl ether) (TBBPA-BAE), TBBPA bis(2,3-dibromopropyl ether) (TBBPA-BDBPE), TBBPS bis(allyl ether) (TBBPS-BAE) and TBBPS bis(2,3-dibromopropyl ether) (TBBPS-BDBPE), based on TLC sample pre-treatment coupled with HPLC-DAD at UV 214 nm. The LODs and LOQs were between 0.023-0.087 μg/g dw and 0.076-0.29 μg/g dw, respectively. The recoveries were between 41-108 % and both % RSD of repeatability and intermediate precision were < 11 %. The method showed a good performance for analyzing natural soil samples collected from BFRs industrial park, suggesting its great application potential for monitoring environmental TBBPA/S and their derivatives.

J. Chromatogr. A 1497, 155-163 (2017). Development of a planar yeast estrogen screen for the determination of estrogen active compounds. Introduction of resorufin-β-D-galactopyranoside, providing the orange fluorescing resorufin after enzymatic cleavage, as the planar yeast estrogen screen (pYES) substrate to determine estrogen active compounds (EAC). For samples containing blue fluorescent components, this substance is better suited than the generally employed substrate 4-methylumbelliferyl-β-D-galactopyranoside, which delivered blue fluorescing 4-methylumbelliferone after enzymatic cleavage by the YES reporter β-D-galactosidase. The mean LOD and LOQ was 3.5 and 6.5 pg/zone for 17β-estradiol (1) and 17α-ethinylestradiol (2), respectively; recoveries were close to 100% for (1) and (2) from spiked water samples in a concentration range of 2–20 ng/L.

J. Planar Chromatogr. 31, 28-35 (2018). HPTLC fingerprint of twenty Bryophyta species on A) silica gel with ethyl acetate ‒ formic acid ‒ acetic acid ‒_x000D_
water 28:3:3:4 and B) RP-18 with methanol – water – formic acid 14:5:1. Detection by spraying with natural products reagent (1 g of diphenylborinic acid 2-aminoethylester in 100 mL of methanol) followed by PEG reagent (5 g of polyethylene glycol in 100 mL of methanol). Qualitative identification under UV 366 nm.

J. Sep. Sci. 40, 4482-4494 (2017). HPTLC fingerprint of Herba Leonuri on RP phase with ethyl acetate – formic acid – acetic acid – water 20:3:3:2. Detection by spraying with 10 % sulfuric acid in ethanol, followed by heating at 105 °C for 10 min. Also HPTLC on normal phase (NP) silica gel with ethyl acetate – formic acid – ethanol 3:2:3. Detection by spraying with bismuth potassium iodide with 1 % iron chloride – ethanol 5:1, followed by heating at 105 °C for 10 min. Qualitative identification under UV 254 nm for the NP system and 365 nm for the RP system. The hRF values of rutin, chlorogenic acid, hyperoside and isoquercitrin in the RP system were 27, 32, 43 and 47, respectively. The hRF values for trigonelline and stachydrine in the NP system were 23 and 25.