J. Planar Chromatogr. 30, 154-163 (2017). HPTLC of chlorpyrifos (1), quinalphos_x000D_ (2), and triazophos (3) on silica gel with n-hexane ‒ acetone 9:1 and on RP-18 with acetonitrile ‒ water 4:1. The results indicated that the hRf values of all three pesticides increased with the polarity of the solvent.

J. Chromatogr. Sci. 54 (7), 1090-1095 (2016). Comparison of the dynamics of peptidization of L-serine (L-Ser), an important proteinogenic amino acid which undergoes spontaneous oscillatory processes of chiral inversion and peptidization with D-Ser and DL-Ser (racemate). The main analytical techniques used in the experiment were TLC-densitometry, HPLC–evaporative light scattering detector and LC–MS. The results showed the differences in peptidization dynamics of the two Ser enantiomers (L and D) and of the racemic mixture thereof (DL) and showed that DL-Ser characterizes with the higher, and L- and D-Ser with the lower peptidization yields.

J. Chromatogr. Sci. 54 (9), 1661-1669 (2016). Development of two sensitive and accurate stability-indicating chromatographic methods for the determination of rafoxanide (RFX): 1) by TLC on silica gel with chloroform – ethyl acetate – toluene – ammonia 50:40:3:1, determination by densitometry at 280 nm; 2) by UPLC. Identification of the degradation products by mass spectrometry and IR spectroscopy. Both proposed methods proved to be accurate, robust, specific and suitable for application as stability-indicating methods for routine analysis of RFX in quality control laboratories.

J. Planar Chromatogr. 30, 405-410 (2017). HPTLC of 200 hydrocarbons containing condensed aromatic rings on silica gel with n-hexane and n-heptane. A magnetic field at constant inductivity (0.44 T), generated by a pair of permanent magnets perpendicular to the direction of chromatogram development was used to investigate its influence in the retention of substances.

CBS 118, 1-4 (2017). Screening of steroids and selective androgen receptor modulators (SARMs) in bodybuilding supplements by HPTLC of methanedienone, ibutamoren, and ostarine on silica gel with n-heptane – ethyl acetate 1:1 (steroids) and dichloromethane – methanol 9:1 (SARMs) to the migration distance of 70 mm. Detection by immersion into (1) toluene sulfonic acid reagent (10 % in ethanol) followed by heating at 150 °C for 3 min, or (2) Seebach reagent (5 g phosphomolybdic acid, 2 g cerium sulfate and 12 mL sulfuric acid made up to a volume of 200 mL with water) followed by heating at 110 °C for 5 min. Detection under UV 254 nm, 366 nm and under white light. Densitometric evaluation by multi-wavelength scan at the respective absorption maxima. For example for the steroid testosterone the LOD was 8 ng/zone (absorbance measurement at 250 nm). Direct elution of target zones into the MS and analysis in positive ionization mode.

J. Chromatogr. Sci. 55, 961-968 (2017). Presentation of two accurate, precise and highly selective stability-indicating methods for simultaneous determination of benztropine mesylate (BNZ) in presence of its hepatotoxic and carcinogenic degradation product, benzophenone (BPH) either in pure form or in the pharmaceutical formulation without any preliminary separation steps. TLC of BNZ and its degradation product on silica gel with hexane – methylene chloride – triethylamine 25:25:3. Quantitative determination by densitometry at 235 nm. The linearity was between 1.5-10 μg/band and 1-10 μg/band for BNZ and BPH, respectively. UPLC of the mixture on a RP C8 analytical column, quantification using a diode array detector at 210 nm. The linearity with UPLC was 20-200 μg/mL and 5-50 μg/mL for BNZ and BPH, respectively. Comparison of the results showed no significant differences between the TLC and UPLC method regarding both accuracy and precision.

Food Chem. 260, 344-353 (2018). HPTLC profiling of phenolic compounds in 50 commercially available beers on silica gel with methyl ethyl ketone – toluene – formic acid 25:15:2. Detection by dipping into a 0.5 % methanolic 2-aminoethyl diphenylborinate solution, followed by drying in the air for 5 min and immersion for 3 s in a 5 % methanolic PEG 400 solution. Image acquisition at UV 366 nm. The HPTLC method was hyphenated to four different assays to demonstrate the fast discovery of single DPPH scavengers, Gram negative (A. fischeri) and Gram positive (B. subtilis) antimicrobials as well as AChE inhibitors in beers. For the DPPH assay, the plate was immersed into a 0.02 % methanolic DPPH_x000D_ solution, followed by drying at ambient temperature (25 °C) in the dark for 30 s and then heated for 30 s in a stream of warm air. Images were acquired every 30 s for a period of 10 min. For the B. subtilis bioassay, the plate was immersed_x000D_ in the prepared bacterial suspension, incubated at 37 °C for 2 h, immersed in a 0.2 % PBS-buffered MTT solution and incubated again at 37 °C for 0.5 h. For the luminescent A. fischeri bioassay, the plate was immersed in the bacterial suspension for 2 s and instant bioluminescence was captured. For the AChE assay, the plate was immersed in the enzyme solution (AChE 666 units plus 100 mg BSA ad 100 mL 0.05M TRIS buffer, pH 7.8), incubated at 37 °C for 25 min, and immersed in a substrate solution (25 mg α-naphthyl acetate and 50 mg Fast Blue salt B ad 90 mL with ethanol – water 1:2). Phenolic compounds in active zones were also characterized by HPTLC-HRMS. Effect-directed fingerprints were investigated for image processing and multivariate data analysis. Isoxanthohumol was found to be the main phenolic beer component that showed the widest spectrum of activities.

J. Chromatogr. A 1533, 199-207 (2018). Presentation of a simple and cost-effective approach for the determination of selenium species in algae and yeast biomass by TLC combined with diode laser thermal vaporization inductively coupled plasma mass spectrometry (DLTV ICP MS), after extraction of freeze-dried biomass in 4M methanesulphonic acid and vaporization of the selenium species from cellulose plates using a continuous-wave infrared diode laser with power up to 4W. Quantification of selenomethionine and selenocysteine with LOD of 3 μg/L in a Se-enriched microalgae Chlorella vulgaris and yeast certified reference material SELM-1. Comparison of the results delivered by TLC-DLTV ICP MS with those obtained by a routine coupling of HPLC to ICP MS showed that both were consistent, moreover, the TLC approach has advantage in capability of analyzing extract containing even undiluted crude hydrolysates.