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).

Marine Drugs 20(4), 270 (2022). Samples were ether glycerols (EG) purified: (A) from Chimaera monstrosa liver oil (Chimaeridae); (B) from mixed liver oil of sharks Centrophorus squamosus (Centrophoridae) and Somniosus microcephalus (Somniosidae); (C) from Macaca fascicularis hearts (Cercopithecidae); (D) from tumors obtained by grafting in mice the human melanoma cell line MDA-MB-435s, and (E) from periprostatic adipose tissue of men with prostate cancer. Reduction of (phospho)ester glycerolipids into EG and fatty alcohols was part of the purification process. Octadecyl-glycerol and octadecenyl-glycerol were used as standards of alkyl- and alkenyl-glycerols, respectively. HPTLC on silica gel previously developed with chloroform – methanol 1:1, air-dried and activated for 30 min at 110° C. Application under nitrogen stream (6 bar). Development with petroleum ether – diethyl ether – acetic acid 60:140:1. After 2 h drying at room temperature under ventilation hood, visualization by 50 s immersing into sulfuric acid (7 % in ethanol), followed by 2 h drying under air-stream, and 14 min heating at 140° C. Plates were documented under white light illumination and densitometry was performed by computered scanning of the pictures. Alkyl-glycerols (mean hRF 34, LOQ 1235 ng/band) and alkenyl-glycerols (mean hRF 44, LOQ 2352 ng/band), present in all samples (except alkenyl-glycerols in shark oil), were quantified after method validation for specificity, sensitivity, accuracy, precision and repeatability. Linearity range was 1000 ng – 7000 ng for both EG types. To confirm the band identification, samples and standards were also submitted to acidic hydrolysis before HPTLC application. In this case, the bands of alkenyl glycerols did not appear, because chlorhydric acid reacted with the vinyl ether bonds to form glycerol and aldehydes.

J Chromatogr A 1638, 461895 (2021). Samples were sphingolipid-rich fractions of unproteinated blood plasma from healthy humans or from Fabry’s disease patients, as well as standards of sphingomyelin (SM) and of globotriaosylceramides (Gb3 = ceramide trihexosides), and related compounds (lyso-ceramide trihexosides, lactosyl ceramide, glucosyl ceramide). HPTLC on silica gel (Lichrosphere with spherical particles) by automated multiple development with a 9-step gradient, starting with pure methanol and ending with dichloromethane – methanol 9:1. Visualization and densitometry under UV 190 nm. Derivatization for Gb3 and derivatives (but not for SM) by immersion into orcinol solution (0.2 %, with sulfuric acid 10 %), followed by 15 min heating at 100 °C and by densitometry under visible light 550 nm. Bands of interest were directly eluted with methanol from underivatized plates into an ion-trap MS, through the oval head of a TLC-MS interface (with stainless steel frit to remove silica gel particles). Two different ionization processes were used: (A) electrospray ionization (ESI, capillary voltage 4 kV, endplate offset voltage -0.5 kV, nebulizer pressure 40 psi, drying gas 9 mL/min at 350 °C); (B) atmospheric pressure chemical ionization (APCI, capillary voltage 2–3 kV, current intensity 4.5 µA, nebulizer pressure 45 psi, drying gas 5 mL/min at 350 °C; vaporization at 450 °C). Full MS spectra were recorded up to m/z 1500 in positive ion mode. The relative ion intensities were used to quantify the detected species. Previous to this study, the precision of the elution head positioning was tested on Gb3 standard zones, comparing 3 positions for analyte elution: from the centre and from each higher or lower side of the band. The same main m/z peaks were observed in the 3 positions, but in different proportions. This was explained by the presence of coeluting Gb3 subclasses (the ceramide moiety CM being either saturated, mono-unsaturated fatty acyl with a slightly higher migration distance, or polar hydroxyl fatty acyl with the opposite effect on migration) and of coeluting Gb3 isoforms (the hexoside moiety consisting of glucose and/or galactose units). This resulted in the broadening and partial splitting of the standard band. In the plasma samples, 19 molecular species of Gb3 were identified (depending on the CM, the sugar isoforms being undistinguishable by MS): 5 with a saturated CM, 7 with two additional double bonds on the CM, 7 with a methylated CM. In case of Fabry’s disease, most Gb3 species with saturated CM were highly increased, whereas other species were decreased.

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).

J. Planar Chromatogr. 33, 169-177 (2020). HPTLC of berberine (1) and 5-fluorouracil (2) in rabbit plasma on silica gel with toluene - methanol - ethyl acetate - formic acid 6:2:6:1. Quantitative determination by absorbance measurement at 266 nm. The hRF values for (1) and (2) were 28 and 57, respectively. Linearity was between 20 and 300 ng/zone for both (1) and (2). Intermediate precisions were below 7 % (n=3). The LOQ was 29 ng/zone for (1) and 26 ng/zone for (2), respectively. Average recovery was 86.5 % for (1) and 87.2 % for (2).

J. Chromatogr. A 1594, 181-189 (2019). Development of a simple and rapid procedure for the determination of quinalphos in human whole blood by HPTLC on silica gel with n-hexane – acetone 9:1 after extraction from spiked blood samples with the optimum solvent, diethyl ether, at pH 3 (average recovery = 93.6%), detection and quantification by densitometry at 325 nm in absorbance mode. Validation by examination of the effect of different organic solvents and pH on the extraction yield of quinalphos, and by investigation of the interference of other organophosphorus pesticides of forensic relevance (not observed). The linearity was in the range of 1 to 100 μg/mL with r2 = 0.9981, the sensitivity (LLOQ) at 1 μg/mL. The within-day precision and between-day precision ranged from 0.2 to 1.0%, and 0.1 to 0.8%, respectively, with an overall average recovery of 91.1% at three concentrations 1, 10, and 50 μg/mL. For different storage conditions for the samples no significant decrease in the concentration of quinalphos was observed. Application of developed procedure in three fatal cases of poisoning.

J. Planar Chromatogr. 32, 149-156 (2019). HPTLC of ondansetron (1) and pantoprazole (2) in pure forms and normal saline intravenous infusions on silica gel with chloroform - methanol - ethyl acetate 3:1:1. Quantitative determination by absorbance measurement at 302 nm. The hRF values for (1) and (2) were 50 and 73, respectively. Linearity was between 30 and 1000 ng/zone for (1) and 50 and 1000 ng/zone for (2). The intermediate precision was below 2 % (n=3). The LOD and LOQ were 8 and 23 ng/zone for (1) and 16 and 47 ng/zone for (2), respectively. Recovery rate was 99.8 % for (1) and 99.9 % for (2).