J. Food Compos. Anal. 126, 105835 (2024). HPTLC of putrescine (1), spermidine (2), and spermine (3) on silica gel with chloroform - triethyl amine 4:1. Quantitative determination by absorbance measurement at 254 nm. Linearity was in the range of 0.2-0.8 mg/mL for (1), 0.1-1 mg/mL for (2) and 0.1-0.8 mg/mL for (3). Intermediate precisions were below 4 % (n=3). LOD and LOQ were 0.07 and 0.21 mg/mL for (1), 0.03 and 0.11 mg/mL for (2) and (3). Recovery was in the range of 96.9-109.4 % for (1), 90.1-109.1 % for (2) and 95.9-109.9 % for (3).

PLoS ONE 18(11), e0295012 (2023). TLC on silica gel to monitor the synthesis of 15 new camphene-based thiosemicarbazones produced by the reaction of camphene thiosemicarbazide either with benzaldehydes, or with acetophenones, or with one of the following molecules: benzophenone, cinnamic aldehyde, ethyl pyruvate, furaldehyde, menthone, pyrrole carboxaldehyde or thiophene-carboxaldehyde. Development with n-hexane – ethyl acetate 3:7 in the case of benzaldehydes, except vanillin; or 7:3 for the vanillin derivative and all others, followed by visualization of products with resublimated iodine. The aldehyde used for compound 15 is in fact vanillin.

Chin J Anal Sci 38 (4), 433-440 (2022). TLC of acetochlor, alachlor, metolachlor, butachlor and pretilachlor in the root vegetables onion and garlic on silica gel with hexane – acetone 4:1. Detection by spraying with 5 % iodized bismuth potassium in acidic aqueous solution. Then QuEChERS (quick, easy, cheap, effective, rugged, safe)-GC-MS/MS method in the selected ion monitoring mode for determination of residues of these compounds after extraction with acetonitrile and acetonitrile - acetic acid and purification by PSA , MWCNTs , GCB and C18 at optimized conditions. The linearity ranged from 0.02 to 2.0 μg/mL for the 5 compounds with the correlation coefficients greater than 0.99, the LOQ was 0.025 mg/ kg, the average recoveries ranged from 72.0 % to 102 % with the relative standard deviations from 0.5 % to 7.9 %.

J. Planar Chromatogr. 36, 71-76 (2023). HPTLC of melamine (1), formaldehyde (2) and genotoxins (3) in bamboo tableware on silica gel with iso-propanol - ethyl acetate - water 10:5:6 for (1), chloroform - dichloromethane - diethyl ether 4:5:6 for (2) and (3). Genotoxin analysis by spraying with Salmonella suspension followed by spraying FDG substrate solution and incubation at 37 °C for 15 min. Qualitative analysis at 254 nm and densitometric absorption measurement at 202 nm for (1) to (3).

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, 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, bmad025 (2023). Standards (separated and mixed) were montelukast sodium (MKT) and loratadine (LRT). Samples were methanolic solutions of commercial tablets, and purified blood plasma as biological fluid, from patients taking MKT or LRT as oral treatment. TLC on silica gel with ethyl acetate – ethanol 9:1. Visualization under UV 254nm. The hRF values were 80 for MKT and 71 for LRT. Densitometric absorbance measurement at 260 nm (20 mm/s scanning speed). System suitability was verified by resolution, selectivity, capacity and absence of tailing. The method was validated for linearity range (0.3–3.6 μg/zone for MKT, 0.2–4 µg/zone for LRT), for precision, for reproducibility, for robustness, and for accuracy expressed as average recovery values (100 % overall mean) at different concentrations. The TLC-densitometric method was also found statistically equivalent (Student’s t-test and F-test) to a previously described method (HPLC – spectrophotometry), but was better in terms of environmental and health impacts, using green analytical procedure index (GAPI) and analytical eco-scale (scores based on solvents/reagents, energy consumption, occupational hazard and waste generation). The TLC method was also compared to three (equally “green”) different analytical methods of spectrophotometry (without chromatography): response correlation, absorptivity-centering and LRT-MKT ratio derivatives. The TLC method was more sensitive (LOQ values were 82 ng/zone for MKT, 20 ng/zone for LRT).

J Chrom Sci, bmad042 (2023). Standards (separated and mixed) were antazoline (ANT) and tetryzoline (TET) hydrochlorides. Samples were one commercial ophthalmic solution containing both molecules (unspiked and spiked), and aqueous humour of untreated rabbits as biological fluid, spiked with various concentrations of ANT and TET. TLC on silica gel with ethyl acetate – ethanol 1:1. Visualization under UV 254 nm. Densitometric absorbance measurement at 220 nm (20mm/s scanning speed). The hRF was 47 for TET and 71 for ANT. System suitability was verified by resolution, selectivity, capacity and absence of tailing. The method was validated for linearity range (0.2 – 18 µg/band), for precision, for reproducibility, for robustness, and for accuracy expressed as average recovery values (100 % overall mean) at different concentrations. The method was also found statistically equivalent (Student’s t-test and F-test) to the official corresponding titrimetric methods of the European Pharmacopoeia. Finally, environmental and health impacts of the methods were qualitatively and quantitatively assessed better as the other described methods, using analytical greenness (AGREE), green analytical procedure index (GAPI), national environmental method index (NEMI), and analytical eco-scale (scores based on solvents/reagents, energy consumption, occupational hazard and waste generation).