Macedonian Journal of Chemistry and Chemical Engineering

Нобелова награда за хемија во 2023 година

Biljana Pejova — 2023-12-26

Добитници на Нобеловата награда за хемија во 2023 год. се: Moungi G. Bawendi, Louis E. Brus и Алексеј И. Екимов за „откривање и синтеза на квантни точки“.

Impressum

Zoran Zdravkovski — 2024-01-11

The first female student from Macedonia to win a medal at International Chemistry Olympiad

Miha Bukleski — 2023-12-29

International Chemistry Olympiad 2022, Tianjing, China

The best achievement of the Macedonian chemistry team at the International Chemistry Olympiad 2023

Miha Bukleski — 2023-12-29

International Chemistry Olympiad 2023, Slovakia and Czech Republic

International Mendeleev Chemistry Olympiad 2023, Astana, Kazakhstan

One-step extraction versus QuEChERS for pesticide analysis in selected fruits and vegetables

Darko Andjelković — 2023-12-24

This research was focused on the performance evaluation of a simple sample preparation involving acetonitrile extraction followed by liquid chromatography/mass spectrometry (LC/MS) analysis. Simplified method validation parameters, along with several other features, were compared to those of the citrate QuEChERS for 19 pesticides analyzed in four representative fruits and vegetables. The results showed comparable performances of the two methods for 5 of the 6 investigated validation parameters. The simplified method had better performance regarding the selectivity, since three analytes experienced a selectivity issue in one of four QuEChERS-treated matrices. Overall, results lead to an assumption that acetonitrile extraction could be reasonably implemented in certain cases of pesticide analysis, as an efficient and economical alternative to the official method. Since the research provides an insight into acetonitrile extraction capabilities in the domain of pesticide analysis in complex matrices, scientists, researchers or analytical practitioners can determine which method is most beneficial for a particular analysis.

Polyol synthesis of Ag nanowires and biocidal activity of the obtained product

Stanislav Kurajica — 2023-12-25

Silver nanowires were prepared by the polyol process with ethylene glycol as a solvent and reducing agent, silver nitrate as a silver source, polyvinylpyrrolidone as a growth-directing agent, stabilizer and agglomeration prevention agent, and copper chloride as a growth control agent. The product was characterized by UV–Vis spectroscopy, scanning electron microscopy, and X-ray diffraction. The biocidal activity of silver nanowires was investigated using the disc diffusion method on the bacteria Bacillus subtilis and Pseudomonas aeruginosa and the fungi Aspergillus niger and Candida albicans. X-ray diffraction and scanning electron microscopy showed that, in addition to silver nanowires, the product also contains quasi-spherical silver nanoparticles and some silver chloride. Based on the results of UV–Vis spectroscopy and scanning electron microscopy, it was estimated that the diameter of the nanowires is 200–300 nm. Nanowires have shown weak bactericidal and good fungicidal activity. Silver nanowires showed particularly good activity in inhibiting the growth of Candida albicans.

Voltammetric biosensors based on metallic nanoparticles synthesized from plant extracts: A short overview of recent achievements

Rubin Gulaboski — 2023-12-24

Since the last decade of the 20^th century, many scientific disciplines have heavily relied on materials with nanometer dimensions. Nanomaterials are already integrated into numerous biomedical and pharmaceutical applications, including the delivery of active substances to specific targets within the body. This has been demonstrated by their contribution to the containment of the recent COVID-19 pandemic. Graphene, silver, gold, and other nanoparticles possess exceptional physical and chemical properties, including increased thermal stability, improved conductivity, and the capacity to host various organic substrates on their surface area. In the past 20 years, a significant field of nanoparticle synthesis has emerged, where eco-friendly reducing agents found in numerous plant species are used. This brief review focuses on the outstanding performance of metallic nanoparticles synthesized using "green methods" in designing voltammetric biosensors. The major goal of this short review is to highlight some of the latest electrochemical advances in exploring metallic nano-systems obtained via phytosynthesis from plant extracts, covering the most notable achievements in the design of amperometric and voltammetric biosensors.

The electrochemical reduction of hydrogen peroxide on a palladium-amorphous carbon composite in an alkaline medium

Jelena Čović — 2023-12-24

The study of hydrogen peroxide reduction in an alkaline aqueous medium on a composite of palladium particles dispersed in an amorphous carbon matrix (Pd@AC) was performed. Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), and X-ray Powder Diffraction (XRD) were used to examine morphology, composition, and crystalline structure. The crystalline structure and size of palladium were analyzed using XRD. The reduction of hydrogen peroxide was studied through cyclic and square-wave voltammetry in an alkaline solution in the absence and presence of dissolved oxygen. The overall electrocatalytic effect of Pd@AC toward hydrogen peroxide reduction strongly depends on the presence of oxygen and the hydrogen peroxide disproportionation reaction in the three-phase system of amorphous carbon, palladium particles, and electrolyte solution.

The net peak splitting phenomenon in square-wave voltammetry – A simple diagnostic tool to distinguish between surface electrode mechanisms associated with different chemical reactions

Rubin Gulaboski — 2023-12-24

Utilizing pulse voltammetric techniques for the electrochemical analysis of lipophilic redox systems has proven to be an effective method for studying a diverse range of redox compounds, from simple molecules to intricate proteins. To extract relevant thermodynamic and kinetic data from electrochemical analysis of redox systems exhibiting strong surface activity, there's a crucial need to decipher the underlying electrochemical mechanism in the system being examined. The "split net peak" phenomenon, a defining characteristic observed in all surface-active redox systems featuring fast electron transfer under square-wave voltammetry conditions, has been investigated in this study to establish diagnostic criteria for identifying surface electrochemical mechanisms associated with preceding, subsequent, regenerative, and reactant-inactivating chemical reactions. This understanding can be achieved by tracking the influence of the chemical reaction rate on the split square-wave voltammetric peaks in a particular electrochemical mechanism. The approach reported in the current work enables a very simple and precise differentiation between the elaborated mechanisms frequently encountered in protein-film voltammetry methodologies.

The influence of different yeast strains and yeast nutrients on the aroma of Krstač and Žižak wines

Valerija Madžgalj — 2023-12-24

Krstač and Žižak are autochthonous grape varieties grown in Montenegro. Although international varieties are more popular, the autochthonous varieties are very important, especially for countries developing tourism. The fermentation aromas produced during alcoholic fermentation contribute significantly to wine quality. The effects of yeasts (Saccharomyces cerevisiae and Saccharomyces bayanus) and yeast nutrients (Fermaid E and Fermaid O) on aromatic compounds in wines were investigated. Using GC/FID-MS analysis, aroma compounds in Krstač and Žižak wines were characterized and quantified. Wines produced with the addition of yeast and yeast nutrients had mostly lower total alcohol content than wines obtained by spontaneous fermentation of Krstač and Žižak varieties. The results of this study showed that the concentration of compounds depends on the yeast strains. The yeast S. cerevisiae (ICV) provided a higher content of higher alcohols, while S. bayanus produced a higher concentration of esters and (medium chain) fatty acids. Total ester content ranged from 3.34 to 11.97 mg/l for Krstač wines and 8.51 to 13.68 mg/l for Žižak wines. Among all wines, Krstač and Žižak wines produced with S. bayanus and Fermaid E addition had the highest concentration of total esters. The yeast nutrients Fermaid E and O emphasized different characteristics of the yeasts. They had a statistically significant effect on the content of ethyl and acetate esters. The highest overall scores were obtained for ICVE and BayE Krstač wines (18.1 out of 20 points) and Žižak ICVE wine (18.2 out of 20 points).

Single-step, electrophoretically deposited hydroxyapatite/poly(vinyl alcohol)/chitosan/gentamicin coating for biomedical applications

Nevena Jaćimović — 2023-12-25

Biocomposite hydroxyapatite/poly(vinyl alcohol)/chitosan/gentamicin coatings were fabricated on titanium by electrophoretic deposition process (EPD) from an aqueous suspension using the constant voltage method. Characterization of the deposited coatings was performed by scanning electron microscopy with field emission (FE–SEM), Fourier transform infrared spectroscopy (FT–IR) and X-ray diffraction (XRD) after immersion in simulated body fluid (SBF) at 37 °C. The concentration of the released gentamicin was determined using a high-performance liquid chromatography (HPLC) coupled with a mass spectrometer (MS). The release profile confirmed an initial “burst-release effect” with ~ 30% of gentamicin released in the first 48 h, which could be of assistance in the prevention of biofilm formation. Antibacterial activity was proven by the agar diffusion method on Staphylococcus aureus TL and Escherichia coli ATCC 25922 bacterial strains. Cytotoxicity was tested by the dye exclusion test (DET) on MRC-5 and L929 fibroblast cell lines, with both coatings expressing nontoxicity. The results showed the high applicability potential of a poly(vinyl alcohol)-based biocomposite coating for medical purposes.

Characterization of tea water extracts and their utilization for dyeing and functionalization of fabrics of different chemical compositions

Leposava Pavun — 2024-01-04

Green, black, rooibos, and hibiscus tea (GT, BT, RT, and HT) aqueous extracts were prepared and characterized in terms of total flavonoids (TFC) and total phenolic (TPC) contents and antioxidant and antimicrobial activities. BT has the highest, while HT has the lowest TFC (1213 vs. 415 mg l^–1), while the extracts’ TPCs (2283 – 7251 mg l^–1) decreased in the following order: BT > GT > RT > HT. Their antioxidant activities of 78.1 – 93.1% and 97.8 – 100% were determined according to DPPH and ABTS methods, respectively. BT and especially GT aqueous extracts possessed mild effects against several microorganisms. All examined extracts have an affinity for dyeing wool, cellulose acetate, polyamide, and cotton, which is proven by the color strength values of 1.65–19.12. Wool, polyacrylonitrile, polyester, polyamide, cotton, and cellulose acetate functionalized with GT aqueous extract inhibited the growth of S. aureus and E. coli, while polyacrylonitrile and cotton also inhibited the growth of E. faecalis, and C. albicans, respectively. Wide inhibition zones for S. aureus were observed for fabrics functionalized with BT aqueous extract. Generally, the investigated fabrics showed very high (81.60 – 100%) ABTS radical scavenging ability independent of the extract used. TPCs have good linear correlations with the antioxidant activities of wool and polyacrylonitrile determined by the DPPH method. Fabrics with different chemical compositions dyed and/or functionalized with GT or BT aqueous extracts can be used to produce high-value-added medical textiles with therapeutic, prophylactic, and protective functions. They can find potential applications in wound treatment, especially in skin wounds that are susceptible to infection with S. aureus. Moreover, wool and cotton functionalized with GT or BT aqueous extract can also be considered for use in disposable medical textiles like bandages and gauze used in the wound-healing process.

Diclofenac analysis in natural waters using UV-visible absorption spectrometric method

Jean-Marie Bakhoum — 2023-12-24

In this work, we developed an UV-visible (UV-VIS) absorption spectrometric method for the quantification of sodium diclofenac in natural waters. Several UV-VIS absorption method parameters were optimized. The maximum absorption wavelength was comprised between 276 and 292 nm, depending on the solvent, with molar absorption coefficients greater than 10⁴ L mol^-1 cm^-1. The linearity of the UV-VIS calibration curves extended over one to three orders of magnitude, with correlation coefficients (R²) very close to unity. The low relative standard deviation (RSD) values indicated a good reproducibility of the measurements. Analytical applications to natural waters yielded satisfactory results with average recovery rates between 94.7 and 99.1%.

Eco-friendly RP-HPLC method for determination of diazepam in coated tablet

Marija Tomić — 2023-12-24

A new eco-friendly RP-HPLC method for determining diazepam in coated tablets was developed and validated. The separation was achieved on a Lichrosper® 100 RP-18 (250 mm × 4 mm, 5 µm particle size) using the isocratic elution mode with a mobile phase composed of a mixture of water (H₂O) and ethanol (EtOH) in a 40:60 (v/v %) ratio and a flow rate of 1.0 mL/min. The injection volume was 10 μL, and the detection wavelength was set at 254 nm. The column temperature was maintained at 35 ºC. The method was validated according to the ICH guideline, emphasizing selectivity/specificity, linearity, sensitivity, accuracy, precision, and robustness. The analytical method greenness score and Eco-scale approach were used for the method’s greenness assessment. The method was applied to determine the assay of diazepam in coated tablets and the uniformity of dosage units by content uniformity.

Applying the method proposed in this study in the pharmaceutical industry is considered environmentally sustainable. It would bring benefits in terms of a safer working environment and reduction of toxic waste formation without compromising the reliability of the analytical results.

Microwave synthesis of novel chenodeoxycholic acid esters and comparative study of chromatographic behavior and lipophilicity

Ksenija Pavlović — 2023-12-24

In this study, eco-friendly microwave-assisted esterification reactions of chenodeoxycholic acid with medium-chain diols (1,2-ethanediol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, and 1,10-decanediol) or tetraethylene glycol were accomplished. The synthesized bile acid esters were obtained with high yields (up to 81 %) and purity in a short reaction time (15 min). It is shown that the microwave technique is a suitable method for the preparation of chenodeoxycholic acid esters. In order to obtain detailed insight into the lipophilic behavior of the studied chenodeoxycholic acid esters, a comparative study of chromatographic behavior and lipophilicity was performed. Also, the present study deals with the estimation of pH – logD profiles in order to get an overview of the changes in lipophilicity related to the pH value changes. The obtained results indicate that studied compounds have logD values in the range acceptable for potential drug candidates. Chromatographic lipophilicity of synthesized chenodeoxycholic acid esters successfully correlate with in silico lipophilicity descriptors.

Experimental and theoretical studies on (2E,5E)-2,5-bis(2-methoxybenzylidene)cyclopentanone: Structural, electrochemical, spectroscopic features, solid-state interactions, molecular docking and adsorption studies onto 2D carbon nanomaterials

Veprim Thaçi — 2023-12-24

A monocarbonyl analog of curcumin, (2E,5E)-2,5-bis(2-methoxybenzylidene)-cyclopentanone (B2MBCP), was prepared and characterized via spectroscopic methods (NMR, UV-Vis, FT-IR, and MS). Furthermore, density functional calculations were implemented to study the molecular structure and spectroscopic features, as well as adsorption properties. In addition, Hirshfeld surface and NBO theoretical analysis were carried out. The reduced density gradient (RDG) analysis via non-covalent interactions (NCI) and interaction region indicator (IRI) indicate the presence of extensive Van der Waals interactions. These interactions are classified in different contributions and energy stabilization from Hirshfeld surface analysis where the dominant type of contacts are H···H contacts. The molecular docking studies of B2MBCP with DNA revealed cooperative interactions that led to intercalation. The results from the cyclic voltammetry (CV) measurements agreed with the calculated energies of the frontier orbitals and the compound structure. Theoretical studies indicated that the relatively flat B2MBCP is adsorbed onto a graphene surface, with a significant adsorption energy of –41.19 kcal/mol. The results of this study provide a better overall picture of the properties of MAC with a cyclopentanone core and can be taken as a useful guide in the search for new biologically active compounds and new possible means of delivery.