J. Planar Chromatogr. 35, 603-608 (2022). HPTLC of berberine (1) and ursolic acid (2) in an Ayurvedic formulation on silica gel with chloroform - acetone - formic acid 12:7:1. Quantitative determination by absorbance measurement at 330 nm. The hRF values for (1) and (2) were 46 and 68, respectively. Linearity was between 200 and 1000 ng/zone for (1) and 500 and 2500 ng/zone for (2). Intermediate precisions were below 2 % (n=9). The LOD and LOQ were 91 and 175 ng/zone for (1) and 153 and 465 ng/zone for (2), respectively. Recovery was in the range of 98 and 102 % for (1) and (2).

J. Chromatogr. A. 1683, 463522 (2022). HPTLC of powdered root sample of Saussurea costus on silica gel with n-hexane - toluene - tetrahydrofuran 10:1:2. Planar bioluminiscent cytotoxicity assay by dipping into concentrated PBS, followed by removal of excess liquid and adding of human embryonic kidney (HEK) 293T cells expressing ELuc, which uses D-luciferin as the substrate for light emission (cell suspension of 5000 cells/μL). To avoid drying out of the plate, two stripes of paper were added to the side of the chamber, which were wetted with 1.5 mL of bidistilled water. After incubation for 6 h, the HPTLC plate was completely dried under cold air, followed by dipping twice into the respective bioluminescent substrate solution for each cell type. Dose-dependent cytotoxicity activity was calculated for the bioluminescence signal reduction. 

Anal. Methods. 11, 4939-4945 (2019). HPTLC of Peganum harmala seeds on silica gel with ethyl acetate - methanol - ammonia (25%) 85:11:4. Detection under UV light at 254 and 366 nm. Track pattern application by applying each reference compound solution (physostigmine: 0.1–1.5 ng/zone; rivastigmine tartrate and piperine: 200–2000 ng/zone). A new piezoelectric spraying workflow was applied for the HPTLC-enzyme assay: the plate was sprayed with the enzyme solution (6.6 units per mL AChE or 3.3 units per mL BChE), followed by incubation at 37 °C for 25 min and spraying with 0.5 mL substrate-chromogenic solution and drying. The enzyme inhibition densitograms of both assays were measured by inverse scan at 546 nm using a mercury lamp. Equivalency of the AChE/BChE inhibition was calculated for two quantitative modes: applied and developed. A higher accuracy was obtained via an appropriate co-developed reference inhibitor for the enzyme inhibition equivalency calculation. 

Anal. Chem. 94, 14554-14564 (2022). The paper describes a completely solvent-resistant 2LabsToGo system and the instructions for its configuration from readily available materials on an open-source basis. A food dye mixture and different water samples were used as proof of concept. The following features and construction of the system were described in detail: the solvent-resistant liquid dosing system, the heatable multifunctional plate holder, development, capturing bioluminescent plate images, detection and digital evaluation, and the software structure compatible with cloud-based database. 

Anal. Chem. 92, 9057-9064 (2020). HPTLC of tanshinones (1) in salvia tea and food preservatives (2) in spiked soft drink on silica gel with petroleum ether - cyclohexane - ethyl acetate 25:14:11 for (1) and petroleum ether - acetic acid - formic acid 36:1:3 for (2). Bioassay was performed by dipping into a A. fischeri suspension. The bioluminescence of the wet bioautogram was recorded for 30 min. Different instrumental setups were investigated to record mass spectra of bioactive compound zones directly out of the bioassay medium. The following orthogonal superhyphenations separated potential coeluting compounds and reduced the interfering bulk: NP-HPTLC-UV/vis/FLD-bioassay-RP/IEX-HPLC-UV/vis-ESI-MS.

Anal. Chem. 88, 10979-10986 (2016). HPTLC of three Salvia miltiorrhiza root samples on silica gel with petroleum ether - cyclohexane - ethyl acetate 25:14:10. Detection under white light, UV light at 254 and 366 nm. Lipophilic antimicrobials were analyzed in direct combination with Aliivibrio fischeri and Bacillus subtilis bioassays. Bioactive zones were further analyzed by mass spectrometry. 

Anal. Bioanal. Chem. doi.org/10.1007/s00216-023-04656-0 (2023). HPTLC of nine convenience tomato products and a freshly prepared tomato soup on silica gel with n-hexane - dichloromethane - methanol - water 40:50:10:1. Detection under white light, UV light at 254 nm, and fluorescence light detection (FLD) at 366 nm. Effect-directed analysis (EDA) with the A. fischeri bioassay as well as α-/β-glucosidase and AChE/BChE enzyme inhibition assays. Metabolism (intestinal digestion of each sample) was simulated and integrated on the same adsorbent surface to study changes in the compound profiles. Further analysis by RP‑HPLC–DAD–HESI‑HRMS/MS using a TLC-MS interface. The method resulted in a 10-dimensional hyphenation including on-surface digestion (1D), planar chromatographic separation (2D), visualization using white light (3D), UV light (4D), fluorescence light (5D), effect-directed assay analysis (6D), heart-cut zone elution to an orthogonal reversed phase column chromatography including online desalting (7D) with subsequent diode array detection (8D), high-resolution mass spectrometry (9D), and fragmentation (10D), for screening of bioactive compounds and their intestinal conversion.

ACS Omega 4, 5038-5043 (2019). HPTLC of Sarcocephalus pobeguinii bark extract on silica gel with toluene - n-butanol - water 35:15:2. Detection under UV 366 nm. Effect-directed detection by dipping into a 0.02 % methanolic DPPH solution, α-glucosidase, and AChE/BChE assays. Fast blue salt B together with 2-naphthyl α-Dglucopyranoside or α-naphthyl acetate was used as substrates for the α-glucosidase or AChE/BChE assays, respectively. For the DPPH reagent, the plate was kept in the dark for 90 s, followed by heating at 60 °C for 90 s. All images were documented in white light illumination. Further analysis by high-resolution mass spectrometry. The method allowed the identification of antidiabetic, cholinesterase inhibiting, and antioxidative activities.