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.

J. Planar Chromatogr. 4, 338-340 (1991). TLC of optical isomers and 22 nitro substituted aromatic hydrocarbons on RP-18 silica with aqueous solutions containing per 100 mL sodium chloride (2.5 g), urea (5.0 g), methanol (30,0 mL), and 0.1 M a-cyclodextrin resp. containing sodium chloride (2.5 g), urea (26.0 g), methanol (30 mL, and 0.1 M ß-cyclodextrin. Detection under UV.

Arzneim.-Forsch./Drug Res. 45 (I), 190-194, (1995). TLC of 12 chloroethyl nitrosourea analogues of cholesterol on silica with dichloromethane, dichloromethane - hexane 7:3, dichloromethane - methanol 49:1. Detection under UV.

Acta Chromatographica 6, 1-4 (1996). TLC of TNT (trotyl) on silica gel with hexane-benzene 1:1. Detection by spraying with phenol red, bromophenol blue, thymol blue, and bromothymol blue, separately, followed by heating at 100 °C for 10 min. These solutions were prepared immediately before spraying of the plates. The hRf value was 50 (± 2). Linearity was between 2.5 and 10 µg/zone. The correlation coefficient was 0.931. LOD (in average, n = 6) was 1.0 µg/zone (phenol red), 1.0 µg/zone (bromophenol blue), 1.5 µg/zone (thymol blue) and 1.5 µg/zone (bromothymol blue).

J. Planar Chromatogr. 8, 78-80 (1995). HPTLC of nitroimidazoles (dimetridazole, metronidazole, ronidazole) in poultry on silica with ethyl acetate. Detection with fluorescamine (detection limit 15 - 20 ng) and by spraying with pyridine, waiting for 1 min and illumination under UV 366 nm (detection limit 3 - 25 ng).

Braz. J. Microbiol. 46, 103-111 (2015). TLC of 2,4,6-trinitrotoluene (1) and two degradation intermediates with nitrite release into the medium by Pseudomonas aeruginosa, 2,4-dinitrotoluene (2) and 4-aminodinitrotoluene (3) on silica gel with ethyl acetate - hexane 2:3. Identification under UV light at 254 nm. The hRF values for (1) to (3) were 83, 67 and 50, respectively.

J. Planar Chromatogr. 7, 461-463 (1994). TLC on silica with benzene - ethyl acetate 10:1. Detection under daylight and UV 254 nm.