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.

J Chromatogr A, 1605, 460366 (2019). Samples were standards and complex mixtures of non-ribosomally synthesized cyclic lipopeptides (CLPs) from Bacillus strains (Bacillaceae) found in soil or in manure: B. amyloliquefaciens (SS-12.6, SS-13.1, SS-27.2, SS-38.4) and B. pumilus (SS-10.7). Two extraction methods were compared: ethyl acetate extraction (Ex1), and the acidic precipitation followed by methanol extraction (Ex2). HPTLC on silica gel with chloroform – methanol – water 65:25:4. Detection under white light, UV 254 nm and 366 nm. Absorption densitometry measured at 190 nm. Derivatization for peptides, amino acids and amino derivatives, by immersion into ninhydrin – collidine reagent (ninhydrin 0.3 %, collidine 5 %, acetic acid 5 %, in ethanol), followed by heating 5 min at 110 °C. Effect-directed analysis using automated immersion: A) for free radical (DPPH•) scavengers; B) for enzymatic inhibition (acetyl-cholinesterase, α-glucosidase); C) for activity against Gram-negative (Aliivibrio fischeri bioluminescence assay) or Gram-positive bacteria (Bacillus subtilis bioassay). Active bands were eluted with methanol through the oval elution head of a TLC-MS interface pump, into a quadrupole-Orbitrap mass spectrometer. Full scan mass spectra (m/z 200−2000) in positive and in negative ionization modes were recorded using heated electrospray ionization (HESI, spray voltage 3.5 kV, capillary temperature 270 °C). Active zones were assigned to be CLPs: iturin A, surfactin dimethyl-ester, and surfactin, fengycin and kurstakin homologues. Ex1 provided richer extracts compared to Ex2. Standards were seen to contain a free radical scavenging impurity.

Chemosphere. 261, 127706 (2020). HPTLC of water samples from four riverbank filtration sites in Germany on silica gel with a gradient development consisting of methanol - formic acid 2000:1 (v/v), dichloromethane and n-hexane in 16 steps. Effect-directed analysis using four bioassays. Baseline toxicity was detected via inhibition of natural bioluminescence of Aliivibrio fischeri (AF). In Bacillus subtilis (BS) assay, metabolic activity of BS cells was detected via the yellow substrate 3-[4,5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT). Neurotoxic effects was analyzed by AChE assay, spraying the substrate indoxyl-acetate onto enzyme-incubated HPTLC plates. In YES assay, estrogenic effects are detected via Saccharomyces cerevisiae BJ3505 strain. 

Anal. Chim. Acta 1174 (2021) 3387022. Presentation of the next generation LabToGo system OCLab2 which was improved and made more robust e.g. by using print and media technologies in chromatography, so-called office chromatography (OC). The first LabToGo methods were developed in the field of food safety and quality for point-of-care or on-site usage. For application volume study,  HPTLC of different methanolic / propanolic Patent Blue V solutions on HPTLC silica gel with ethyl acetate - methanol - water - acetic acid 65:23:11:1 up to 50 mm. Evaluation in white light and  absorption measurement at 635 nm. For performance tests of plate imaging, HPTLC of benzoic acid and sorbic acid acid on HPTLC with ethyl acetate - toluene - acetic acid 25:25:1. For study of the illumination homogeneity, HPTLC of either sorbic acid, 7-hydroxy-4-methylcoumarin, or Patent Blue V on amino phase, evaluation at 254 nm (sorbic acid), 366 nm (7-hydroxy-4-methylcoumarin) and in white light (Patent Blue V), and in the OCLab2 at 278 nm, 365 nm, and white light, respectively, and scanning the plates at 254 nm 366 nm and 635 nm, respectively. For analysis of food dye mixture by OCLab2, HPTLC on silica gel with ethyl acetate - methanol - water - acetic acid 65:23:11:1 up to 5 cm, drying and capturing of plate images by the OCLab2 at 515-525 nm, 620-630 nm and 465-475 nm, video densitometry and evaluation using the open-source quanTLC software. For analysis of Stevia leave samples, the ethanolic extracts and four calibration levels of a steviol glycoside mixture were applied by OCLab2 for the hydrophilic interaction liquid chromatography (HILIC) separation on HPTLC silica gel with acetonitrile - water 5:1. Derivatization with 2-naphthol sulfuric acid reagent at evaluation in white light. For analysis of water and environmental samples, ink-printing the prepared samples on HPTLC silica gel MS-grade, focusing using acetone - water 4:1 up to 13 mm, drying,  developing with ethyl acetate - toluene 1:1 up to 70 mm, drying and capturing the plate images in white light, 254 nm and 366 nm. For biological detection, spraying the plate with A. fischeri bacteria suspension and capturing of images over 36 min with an exposure time of 60 s and a trigger interval of 3.0 min. 

Frontiers in Marine Science 7, 266 (2020). Methanol extracts from marine sponge Haliclona cnidata (Chalinidae) submitted to different stresses (antibiotics and/or darkness) were separated on HPTLC silica gel with an automated 15-step gradient based on methanol, dichloromethane and n-hexane. Bioluminescence was recorded after immersing the HPTLC plates into Aliivibrio fischeri suspension. Antibacterial activity and quorum sensing enhancement were analysed on software, and Pearson’s similarity coefficient was applied to generate similarity matrices for cluster analysis (UPGMA, Unweighted Pair Group Method with Arithmetic Mean). Only slight differences were observed, especially in QS enhanced zones in stressed vs. control cultures.

J. Spectroscopy & Spectral Anal. 41 (2), 388-394 (2021). SERS, as a fast and sensitive analytical technology, is widely employed in the fields of analytical chemistry, environmental detection and food safety. However, the real-life samples are mostly mixtures, and an accurate determination of the analytes in complex samples cannot be performed directly by using SERS. TLC as a separation technique is easy to operate, low cost, fast and high-throughput, and has been widely used in the fields of synthetic chemistry, analytical chemistry, medicinal chemistry, and food science. Further, the zones isolated by TLC are first visualized using iodine vapor coloring or fluorescence, and then combined with SERS for efficient qualification and quantitation of the zones of interest. Therefore, the technology of TLC combined with SERS (TLC/SERS) suits rightly for determination of various kinds of complex samples. Moreover, due to the small sample size and the relatively simplicity of the experimental equipment used, it is also suitable for the rapid field screening and detection of relatively complex samples. Introduction of the enhancement mechanism of SERS and the preparation of the active substrate, and demonstration of the broad prospects of TLC/SERS application in the fields of environmental pollutant analysis, food safety monitoring, traditional Chinese medicine and biomedicine identification etc by providing a set of successful application examples.

Chemosphere. 233, 936-945 (2019). HPTLC of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in marine sediments on silica gel with n-hexane - dichloromethane - toluene 14:5:1. Qualitative identification using the wavelengths 190-310  nm. Toxicological potential of the sediment samples was determined by the intrinsic fluorescence of Aliivibrio fischeri by dipping into the bacteria solution and analysis with a BioLuminizer. 

Chemosphere. 87, 265-272 (2012). HPTLC of different dyes, namely Scarlet RR
(1), Rubine GFL (2), Brilliant Blue R (3), Navy Blue 2R (4) and Red HE3B (5) and ethyl acetate extracted metabolites (6) on silica gel with toluene - ethyl acetate - methanol 7:2:1. Quantitative determination by absorbance measurement at 280 nm at various time intervals (0-96 h). The hRF values of (1) to (5) were 90, 82, 79, 69 and 49, respectively. The hRF values of (6) were 86, 63, 56, 44, 34, 27, 18, 11 and 5. The method allowed to study the progressive decolorization and preferential degradation of the dyes within a mixture by Glandularia pulchella.