J Chrom Sci, bmad045 (2022). Standards were azilsartan medoxomil (AZL) and cilnidipine (CLN). Samples were acetonitrile solutions of commercial tablets of AZL and CLN, and purified human blood plasma as biological fluid spiked with AZL and CLN. The following method was developed by a software-assisted AQbD approach (analytical quality by design): (1) Taguchi orthogonal array design was implemented in 8 screening experiments in order to identify the 3 critical method variables (CMVs), which were: volume ratio of toluene – ethyl acetate, volume of methanol and saturation time. These CMVs had statistically significant impact (one-way ANOVA and Pareto charts) on the 3 critical analytical attributes (CAAs, they were: resolution between AZL and CLN and their hRF values). (2) To optimize these CMVs, the Box–Behnken design was implemented in 15 software-proposed experiments; the impacts of the 3 CMVs on the 3 CAAs were evaluated by ANOVA, multiple regression analysis, and 2D and 3D contour plots; the response surface analysis allowed the software to find a mathematical (quadratic or linear) equation for each CAA, based on the CMVs values. (3) The optimal CMVs ranges were determined by defining an analytical design space (ADS) on the superposed contour plots, and one TLC condition was selected as analytical control point.
TLC on silica gel pre-washed with 10 mL methanol, dried and activated 15 min at 110° C. Separation with toluene – ethyl acetate – methanol 13:3:4 after 15 min pre-saturation with 35 % relative humidity. Absorption measurement at UV 254 nm. The hRF values were 49–51 for AZL and 70–71 for LRT. Linearity range was 400–2000 ng/zone for AZL and 100–500 ng/zone for CLN. Intermediate precision was below 1.6 % (n=3). LOQ were 121 ng/zone for AZL and 34 ng/zone for CLN. Recovery rates were 99.3–99.7 % for AZL and 98.1–99.5 % for CLN. Recovery rates from spiked plasma were 83.3 % for both molecules.

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.

Chromatographia 25, 82-86 (1988). Determination of the lipophilicity of 33 nitrostyrene derivatives by reversed-phase TLC on three alkyl- bonded silicas with methanol. Discussion of the relationship between RM value of each compound and the concentration of the organic solvent, the retention strength and selec tivities of the three bonded phases, and the impact of the change of methanol concentration on the retention.

J. Planar Chromatogr. 1, 70-72 (1988). TLC of the N, N’-dimethylamino derivative of 1-nitropyrene on silica and octadecyl-bonded silica. Quantification by fluorodensitometry. Detection limit, ˜ 10pg. Comparison of the fluorescence intensity and the stability of the N, N’-dimethylamino and the amino derivatives of the compound.

J. Chromatogr. 473, 287-292 (1989). Presentation of a selective procedure for the detection of nitrones and nitroxide radicals in the presence of amine N-oxides on the TLC plate based on the application of trifluoroacetic anhydride-sodium iodide reagent. Discussion of possible interferences and their elimination.

J. Planar Chromatogr. 2, 133-137 (1989). The ion-pairing characteristics of tetraalkylammonium salts and cetrimide and also of tricaprylmethylammonium chloride were studied. In eluents containing 50% methanol and 0.05 mol/L ion-pairing reagent, the Rf values of salicylic acid derivatives displayed the following sequence: tetrabutylammonium hydrogensulfate > cetrimid > tricaprylmethylammonium chloride. On reversed-phase layers, the pH had no effect on retention. With increasing concentration of methanol the retention of the compounds decreased. TLC on RP-8 and (HPTLC) silica with mixtures of water and organic solvents containing NaCl and Bitton-Robinson buffer. Detection under UV 254 and 366 nm.

J. Chromatogr. 516, 467-472 (1990). TLC of nitroso compounds on silica with acetone. Derivatization by spraying with sodium iodide solution and subsequently with trifluoroacetic anhydride solution: brown spots on white background, stable for 20 min.

Proc. 6th Int. Symp. Instrum. Planar Chromatogr., (Interlaken 1991), Inst. Chromatogr., Bad Dürkheim, FRG, 409-417 (1991). TLC of 2,4,6-trinitrotoluene and its metabolites on silica with benzene - ether - methanol 60:3:1. Quantification by densitometry by absorbance at 260 nm. The method is well suitable for screening large numbers of samples as well as for research of the toxicology of the compounds in human body.