J. Sep. Sci. 46, 2300059 (2023). HPTLC of iridoid and iridoid glycoside in Premna fulva on silica gel with ethyl acetate - n-butanol - water 3:1:4. Detection by spraying with 10 % sulfuric acid - ethanol chromogenic agent, followed by heating. The system showed a hRF values from 30 and 70. The method was applied for candidate solvent-system prediction with a generally useful estimate of the solvent systems (GUESS). Further analysis by high-speed counter-current chromatography.

J Pharm Bioallied Sci 15(Suppl.2), S948-S951 (2023). Sample was the ethyl acetate fraction of an ethanolic extract of Viola odorata aerial parts (Violaceae). Standards were coumarinic compounds: esculetin (1) and umbelliferone (2). TLC and HPTLC on silica gel with toluene – ethyl acetate – formic acid 5:4:1. Visualization under UV 254 nm and 366 nm; densitometric scanning at 366 nm. Both (1) and (2) were found in the extract (hRF values 30 and 53, respectively, in TLC). Alternative mobile phases were also tested (TLC only): toluene – ethyl acetate 1:1 (hRF values 47 and 68) and chloroform – methanol 97:3 (hRF values 20 and 41).

J. Planar Chromatogr. 36, 63-70 (2023). HPTLC of quercetin (1), berberine (2), rutin (3) and curcumin (4) in a polyherbal formulation on silica gel with toluene - ethyl acetate - methanol - formic acid 10:6:4:1. Quantitative determination by absorbance measurement at 366 nm for (1) to (3) and 425 nm for (4). The hRF values for (1) to (4) were 57, 30, 9 and 66, respectively. Linearity was in the range of 500-3000 ng/zone for (1), 200-700 ng/zone for (2), 1000-6000 ng/zone for (3) and 100-350 ng/zone for (4). Intermediate precisions were below 2 % (n=6). LOD and LOQ were 119 and 362 ng/zone for (1), 33 and 100 ng/zone for (2), 248 and 750 ng/zone for (3) and 14 and 42 ng/zone for (4). Recovery was between 95 and 102 % for (1) to (4).

J Chrom Sci, bmad055 (2022). Standards of antiglycemic drugs were metformin hydrochloride (S1, a biguanide), glibenclamide (S2 = glyburide, a sulfonylurea), pioglitazone hydrochloride (S3, a thiazolidinedione), repaglinide (S4, a glinide). Samples were methanolic solutions of commercial tablets of S1 with each of the other molecules. The following method was developed by a software-assisted AQbD approach (analytical quality by design): (1) Several TLC separations were tried with toluene together with other solvents and with acidic or basic modifiers, with also variations of 24 method or instrumental parameters. (2) Principal component analysis (PCA) was performed in order to identify two principal components (PCs) responsible for 98 % of the observed variations: namely, resolution and tailing factor. Three critical method parameters (CMPs) had a statistically significant impact on the PCs: mobile phase (MP) composition, ammonium acetate concentration in MP, and saturation time. (3) To optimize these CMPs, the Box–Behnken design was implemented in 15 software-proposed experiments; the impacts of the 3 CMPs on the 2 PCs were evaluated by ANOVA, multiple regression analysis, and 2D and 3D contour plots. (4) The optimal CMPs ranges were determined by defining a MODR (method operable design region) 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 10 min at 100° C. Separation with toluene – ethyl acetate – methanolic solution of 4 % ammonium acetate 7:7:6 after 15 min pre-saturation with 35 % relative humidity. Absorption emasurement at UV 254 nm. The hRF values were 13 for S1, 72 for S2, 82 for S3, 38 for S4. LOQ were 263, 387, 73 and 35 ng/zone, respectively. Linearity range was 25–75 µg/zone for S1, 100–300 ng/zone for S2 and S4, 750–2250 ng/zone for S3. Intermediate precision was below 2 %. For accuracy tests, recovery rates were between 97.6–101.4 %.

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.

J. Planar Chromatogr. 35, 593-602 (2022). HPTLC of lactucin (1) and lactucopicrin (2) in the whole herb of Cichorium glandulosum on silica gel with ether - ethyl acetate 1:5. Quantitative determination by absorbance measurement at 256 nm. The hRF values for (1) and (2) were 42 and 65, respectively. Linearity was between 498 and 2988 ng/zone for (1) and 499 and 2994 ng/zone for (2). Intermediate precisions were below 5 % (n=6). Average recovery was 100.0 % for (1) and 99.5 % for (2). 

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.

Heliyon 9(2), e13469 (2023). Samples were methanolic extracts of different organs (bark, leaves, fruit pericarps, roots, twigs, seed coats and seedlings) of Dysoxylon binectariferum (= D. gotadhora = D. ficiforme, Meliaceae), as well as rohitukine (chromone piperidine alkaloid) isolated from a bark Soxhlet extract through column chromatography. TLC was used to monitor the purity of rohitukine isolation and to compare the fingerprints of the organ extracts. TLC on silica gel in 2 steps, successively with ethyl acetate – hexane 2:1, and with methanol – chloroform – dichloromethane 4:4:1. Visualization under UV 254 nm and 366 nm. Rohitukine (hRF 16) was very concentrated in bark, but present also in pericarps, leaves, twigs, seed coats and seedlings. (Editors note: Mobile phases and distribution of rohitukine were explained directly by the author (successive 2-step development, not biphasic system). The TLC figures did not show unequivocally the presence in roots, but it was confirmed by the author (and already quantified by other methods in  doi.org/10.1371/journal.pone.0158099).