J Chromatogr A, 1619, 460945 (2020). Samples were lamotrigin as standard, or extracted with an oil-in-water microemulsion (10 µL butyl acetate, 4 mL n-butanol, 925 mg sodium dodecyl sulphate, 8.6 mL water) either from patients’ raw plasma (for separation from blood proteins) after spiking, or from commercial tablets dissolved in methanol. TLC on silica gel with a water-in-oil microemulsion of 9 mL butyl acetate, 1 mL n-butanol, 250 mg sodium dodecyl sulphate, 250 µL water. Both optimal microemulsions were predicted using Taguchi orthogonal array and Plackett-Burman design. Evaluation in UV 254 nm, quantification from the digital picture using four image processing software programs. For lamotrigin (hRF 24), limits of quantification were 170 ng for pure drug and 10 ng for spiked plasma. Linearity (in range 20–200 ng/spot) was directly obtained for the calibration curve in spiked plasma; however, for pure drug, linearity was obtained only when using log values of the calculated densities (300–3000 ng/spot).

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.

J. Planar Chromatogr. 34, 549-557 (2021). HPTLC of brexpiprazole (1) and sertraline HCl (2) on silica gel with n-propanol - hexane - toluene - triethylamine 70:20:10:1. Quantitative determination by absorbance measurement at 254 nm. The hRF values for (1) and (2) were 36 and 47, respectively. Linearity was between 4500 and 15000 ng/zone for (1) and 90 and 300 ng/zone for (2). Interday and intra-day precisions were below 4 % (n=3). The LOD and LOQ were 163 and 495 ng/zone for (1) and 35 and 107 ng/zone for (2), respectively. Recovery was between 99.5 and 101.1 % for (1) and 99.4 and 102.0 % for (2).

J. Sep. Sci. 44, 530-538 (2021). HPTLC of tamsulosin (1) and tadalafil (2) in presence of their degradation products (2) and (3) on silica gel with ethyl acetate - toluene - methanol - ammonia 20:10:20:3. Quantitative determination by absorbance measurement at 280 nm. The hRF values for (1) to (4) were 55, 68, 14 and 24, respectively. Linearity was between 0.5 and 25 µg/zone for (1) and (2). Intermediate precision was below 2 % (n=3). Average recovery was 99.7 % for (1) and 100.3 % for (2).

J. Planar Chromatogr. 33, 647-661 (2020). HPTLC of empaglifozin (1) and linagliptin (2) on silica gel with chloroform - methanol - ammonia (25 %) 100:10:1. Quantitative determination by absorbance measurement at 225 nm. The hRF values for (1) and (2) were 31 and 71, respectively. Linearity was between 100 and 5000 ng/zone for (1) and 50 and 2500 ng/zone for (2), respectively. Intermediate precision was below 2 % (n=3). The LOD and LOQ were 32 and 97 ng/zone for (1) and 14 and 42 ng/zone for (2), respectively. Average recovery was 100.1 % for (1) and 99.9 % for (2). Comparison with a similar TLC method showed no significant statistical differences.

J. Planar Chromatogr. 33, 631-646 (2020). HPTLC of azilsartan medoxomil (1) and chlorthalidone (2) on silica gel with toluene - methanol - ethyl acetate - formic acid 35:10:5:1. Quantitative determination by absorbance measurement at 241 nm. The hRF values for (1) and (2) were 55 and 36. Linearity was between 800 and 4000 ng/zone for (1) and 250 and 1250 ng/zone for (2), respectively. Intermediate precision was below 2 % (n=3). The LOD and LOQ were 15 and 44 ng/zone for (1) and 10 and 32 ng/zone for (2). Recovery was between 100.8 and 101.7 % for (1) and 99.4 and 101.0 % for (2).

J. Planar Chromatogr. 33, 231-244 (2020). HPTLC of apremilast on silica gel with toluene - methanol - ethyl acetate 7:2:1. Quantitative determination by absorbance measurement at 241 nm. The hRF value for apremilast was 63. Linearity was between 200 and 1000 ng/zone. Inter-day and intra-day precision were below 1 % (n=3). The LOD and LOQ were 4 and 13 ng, respectively. Recovery rate was between 99.7 and 100.0 %. Apremilast was subjected to acidic, alkaline, oxidative, dry heat, neutral, and photolytic degradation conditions. The method was implemented using a quality risk management and quality by design approach for regulatory requirements.