Abstract Composition of conductive inks plays a decisive role in determining both printability and electrochemical performance of screen-printed electrochemical sensors. In this work, composite conductive inks based on graphitic carbon nitride (g-C 3 N 4 ) and activated carbon (AC) were prepared with systematically varied filler ratios and evaluated by rheological measurements, scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. All inks exhibited shear-thinning behavior suitable for screen printing, while increasing the g-C 3 N 4 content enhanced the low-shear viscosity and promoted rapid structural recovery after shear. Scanning electron microscopy revealed that nanosized g-C 3 N 4 filled the interparticle voids between larger AC particles, producing a denser and more homogeneous composite microstructure. Electrochemical performance was evaluated using a [Fe(CN) 6 ] 3−/4− redox probe. Increasing the AC fraction reduced the peak-to-peak separation from 130 mV for pure g-C 3 N 4 electrode to 100 mV for the 50:50 and 25:75 composites, indicating more facile interfacial charge-transfer kinetics, although the associated Faradaic peak currents decreased with the increasing AC content due to lower density of g-C 3 N 4 -associated redox-active sites. Electrochemical impedance spectroscopy showed a substantial decrease in charge-transfer resistance from 148.5 Ω cm 2 for pure g-C 3 N 4 to 7.2 Ω・cm 2 for g-C 3 N 4 :AC (25:75) composite, outperforming even pure AC electrode (16.9 Ω・cm 2 ). The results demonstrate synergistic interaction between both conductive components. Both materials, g-C 3 N 4 and AC, provide electrochemically active surface sites that promote the Faradaic response, whereas AC establishes an efficient conductive network that facilitates charge transport. The optimized g-C 3 N 4 :AC (25:75) represents a promising conductive ink for the fabrication of low-cost, reliable, screen-printed electrodes that can be readily modified through further surface or bulk functionalization for diverse electrochemical sensing applications.
Abstract A simple differential pulse voltammetric procedure was developed for the determination of the H 1 -antihistamine fexofenadine in commercial pharmaceutical formulations using a bare glassy carbon electrode. The electrochemical behavior of fexofenadine was investigated by cyclic voltammetry in phosphate buffer solutions. The analyte provided an irreversible anodic signal at approximately +0.75 V versus an Ag/AgCl/3 mol·L −1 KCl reference electrode in phosphate buffer at pH 10, where the highest current response was obtained. The influence of scan rate indicated that the oxidation process was predominantly diffusion-controlled. Differential pulse voltammetry was optimized and then used for quantitative analysis. Under the optimized conditions, the method provided a linear concentration range from 9.5 to 67.9 μmol·L −1 , a detection limit of 2.7 μmol·L −1 , and repeatability expressed as a relative standard deviation of 4.8 % for twelve replicate measurements. The influence of selected tablet excipients, including glucose, sucrose, starch, and cellulose, was evaluated, with changes in the integrated fexofenadine response remaining below 5 % at all tested mass ratios. The proposed procedure was applied to the assay of two commercial fexofenadine tablet products, Allegra ® 120 mg and Ewofex ® 120 mg, using the standard addition method, providing recoveries of 99.4 % and 98.7 %, respectively. The method offers a simple option for the differential pulse voltammetric assay of fexofenadine in tablet formulations.
Abstract Backfat fatty-acid composition in Mangalica pigs was evaluated under four practical on-farm feeding regimens: a standard diet, two corn-concentrate diets containing approximately 46.5 % and 93 % corn, and a pasture-mimic diet based on lucerne pellets with supplemental boiled acorns. Sixty pigs were allocated to the four regimens and slaughtered in three batches. Backfat fatty acids were analysed as methyl esters by gas chromatography with flame-ionisation detection and expressed as relative percentages of total detected fatty acids. Two-way analysis of variance showed that feeding regimen, slaughter batch, and their interaction influenced the relative proportions of selected fatty acids. Oleic acid remained predominant in all regimens, but the response of palmitic, stearic, and linoleic acids was stage-dependent. The high-corn regimen differed most clearly in the final batch, with higher palmitic and stearic acid and lower linoleic acid, than the other feeding regimens. The results indicate that feeding strategy can modulate Mangalica backfat composition although the effect depends strongly on the finishing stage.
Abstract In this study, the effect of the plant alkaloid cryptopleurine (CRP) on the cytotoxic activity of cisplatin (CDDP) in non-small cell lung carcinoma A549 cells was investigated. Cells were treated with various concentrations of CRP and CDDP, either individually or in combination. Cell viability was assessed using the MTT assay, and drug interactions were evaluated employing the Chou-Talalay method. The results did not demonstrate a synergistic interaction between CDDP and CRP, instead, the combination exhibited an antagonistic effect in vitro. Further analyses using flow cytometry and fluorescence microscopy revealed no significant induction of apoptosis following combined treatment. Most cells remained viable and only a minimal increase in necrosis was observed. While morphological alterations and reduced cell proliferation were detected, these effects did not correspond to classical apoptotic features, suggesting the involvement of alternative non-apoptotic mechanisms. These findings indicate that CRP does not enhance CDDP cytotoxicity and should not be considered a chemosensitizer of CDDP. Rather, CRP may be more appropriately evaluated as an independent or alternative approach under the tested conditions.
Abstract This study focuses on optimising the pre-treatment, derivatisation processes, and gas chromatography conditions for the determination of lactose in liquid dairy products. Efficiency of sample preparation consists in the coagulation of protein components in methanol, centrifugation, and subsequent drying in a nitrogen stream. Derivatisation of the monitored carbohydrates is performed using a two-step silylation process. The samples were analysed using gas chromatography with flame-ionisation detection (GC-FID). Based on the calibration of lactose content in the range of 0.1—10 % w/v, quantitative determination of this disaccharide was performed in 18 milk samples. The paper presents the results of quantitative analysis as well as dosing and derivatisation repeatability. This method compensates for time-consuming sample preparation by reducing the separation time of mono- and disaccharides to 16 minutes.
