Macedonian Journal of Chemistry and Chemical Engineering

Impressum

2024-12-31T08:09:16-08:00

Spectrophotometric determination of quercetin using micelles of cetyltrimethylammonium bromide in a low ratio methanol–water mixture

2024-05-08T21:59:06-07:00

A simple and achievable UV-Vis spectrophotometric method for the micro-quantitative determination of quercetin has been developed and validated. This method relies on the formation of supramolecular assemblies of quercetin (QR) and the cationic surfactant cetyltrimethylammonium bromide (CTAB) in a 5 % methanolic aqueous solution. In this solvent medium, CTAB in the presence of QR has a critical micelle concentration of 1.2·10^-3 mol l^-1 at 24 °C, determined through conductometry. Important analytical parameters such as wavelength, composition of methanol-water mixture, CTAB concentration (c_CTAB), and pH were optimized. Under the optimum experimental conditions (l = 397 nm, 5 % methanol as solvent, c_CTAB = 2.0·10^-3 mol l^-1, and pH = 6.0), Beer's law was valid for QR concentrations up to 16.9 mg ml^-1. The Ringbom optimum QR concentration range was 1.0 - 16.9 mg ml^-1. The method sensitivity was 2.03·10⁴ l mol^-1 cm^-1 (the molar absorptivity) and 0.13 mg ml^-1 (limit of detection). The applicability of the proposed method for quantifying QR in pharmaceutical formulations was demonstrated. Furthermore, the proposed UV-Vis spectrophotometric method was successfully applied to the reliably assay of QR, even in the presence of vitamin C.

Establishment, evaluation and application of a gas chromatography-mass spectrometry method for quantification of volatile organic compounds in ambient air using anisole as an internal standard

2024-08-23T22:32:51-07:00

Gas chromatography coupled with mass spectrometry (GC-MS) is a standard analytical method for identifying specific volatile organic compounds (VOCs) in urban air samples. Quantification ideally relies on calibration curves using standards for each compound. However, due to the variable composition of VOCs and the limited availability of all standards, this strategy is challenging and not always feasible. Quantification using an internal standard is a simple and accurate approach, as it involves the simultaneous analysis of the internal standard and analytes, eliminating the need for a calibration curve if their concentrations fall within the linear dynamic range. In this study, quantification of VOCs from different chemical classes has been evaluated using a single standard mixture and anisole as an internal standard and compared to the external calibration as standard method for quantification by GC-MS. Both methods showed comparable results, with a relative error within ±30% of the theoretical concentration. Linearity was confirmed in the range from 100 to 4000 μg/L, and the relative standard deviation (RSD) of the relative response factors (RRFs) met the acceptance criteria of ≤30% for each target VOC. Toluene, chlorobenzene, C₆-C₂ and C₆-C₃ substituted benzenes yielded similar average RRFs, ranging from 1.280 to 1.601 with an RSD of 7.83%. The methods were applied for quantification of VOCs in ambient air on real samples collected on Radiello adsorbents at one urban location. Using anisole as an internal standard proved to be a simple and reliable method for determining VOC concentrations, offering a convenient alternative to external standard calibration.

Quantification of diclofenac in natural waters by the photo-induced fluorescence (PIF) method

2024-07-11T00:11:02-07:00

A photo-induced fluorescence (PIF) method was developed for the quantification of diclofenac sodium, sodium 2-[2-(2,6-dichloroanilino)phenyl]acetate (NaDCF), in natural waters. Since diclofenac is not naturally fluorescent, its photoconversion under UV irradiation was carried out to produce highly fluorescent photoproduct(s) in various media (water, methanol, isopropanol, acetonitrile, ethyl acetate, dimethyl sulfoxide (DMSO), and a water-isopropanol mixture). The photoproduct responsible for the intense fluorescence of NaDCF in aqueous media was identified as chloro-carbazole by gas chromatography-mass spectrometry (GC-MS). Several PIF parameters were optimized. Using the PIF method, a highly fluorescent diclofenac photoproduct was obtained at λ_ex/λ_em = 235/360 nm, with optimum fluorescence achieved after 10 min irradiation in a water-isopropanol mixture (90:10 v/v). The limit of detection (LOD) and quantification (LOQ) for diclofenac sodium in this medium were 0.11 ng ml^–1 and 0.37 ng ml^–1, respectively, with low relative standard deviation (RSD) values. The PIF calibration curves demonstrated good linearity, extending over one to three orders of magnitude, with correlation coefficients (R²) near unity, indicating good reproducibility. Analytical applications of this method to natural water samples yielded satisfactory results, with average recovery rates ranging from 84.77 to 101.72 %.

Бојан Шоптрајанов (1937–2024) IN MEMORIAM

2024-12-30T23:02:05-08:00

50 Години од излегувањето на првиот број на MJCCE

2024-12-30T23:06:40-08:00

На 5 јуни 2024 г. во Македонската академија на науките и уметностите беше одбележен јубилејот 50 години од излегувањето на првиот број на Гласникот на хемичарите и технолозите на Македонија. Во присуство на претходни главни и одговорни уредници, секциски уредници, рецензенти, автори, колеги од Институтот за хемија, Технолошко металуршкиот факултет и поддржувачи и гости, кусо обраќање со преглед на историјата и еволуцијата имаше проф. Зоран Здравковски, сегашниот главен и одговорен уредник на списанието.

27th Congress of SCTM

2024-12-30T23:37:41-08:00

The 27^th Congress of SCTM organized by the Society of Chemists and Technologists of Macedonia took place in Ohrid, Macedonia, September 25^th – 28^th, 2024. With 4 plenary sessions, 9 invited lecturers from Italy, Spain, Serbia, Czech Republic, Denmark, and the United Kingdom and almost 200 presentations by 550 authors and co-authors from the region and much beyond, it made it a truly international congress, where a diverse array of topics were presented, which reflect the great energy and commitment of the scientific community. From discoveries in nanomaterials, to advances in biotechnology, electrochemistry, green chemistry to the latest pharmaceutical research, each abstract demonstrates the extraordinary flexibility and ingenuity of our colleagues. It is particularly important to mention the wide range of oral and poster presentations by researchers representing Austria, Azerbaijan, Bosnia and Herzegovina, Bulgaria, Croatia, Germany, Greece, Italy, Kosovo, Montenegro, Poland, Serbia, Slovenia, Spain, Romania and Russia.

Извештај од натпреварите по хемија за 2023/24 учебна година

2024-12-30T23:48:16-08:00

Секцијата за образование при Сојузот на хемичарите и технолозите на Македонија и оваа година успешно ги организираше и реализираше натпреварите по хемија за основно и средно образование, за што СХТМ е акредитиран од Министерството за образование и наука.

Macedonian chemistry team makes history with its first silver medal at the International Chemistry Olympiad

2024-12-30T23:56:17-08:00

This year marked the 10^th participation at the International Chemistry Olympiad (IChO) and the 5^th at the International Mendeleev Chemistry Olympiad (IMChO) since the Society of Chemists and Technologists of Macedonia (SCTM) began organizing and selecting the Macedonian Olympic team. This milestone was celebrated with the team’s greatest achievement to date: at the 56^th IChO, Macedonia won its very first silver medal, along with another bronze. The talented students once again demonstrated that success is followed by hard work and dedication.

Preparing the final nails to seal the coffin of genuine science

2024-11-25T08:04:32-08:00

Science is meant to be shared and discussed, not sold. However, over the past two decades, the phrase "publish or perish" has led significantly to the decline of genuine scientific inquiry. Today's science is often more about profit than sharing knowledge. Neuropsychologist Bernhard Sabel, using a fake-paper detector developed by him, was "stunned" to discover that after screening approximately 5000 papers, up to 34 % of neuroscience articles published in 2020 were either fabricated or plagiarized. In medicine, the rate was 25 %. Currently, more than 11,000 scientific journals operate based on a pay-to-publish open access model (excluding the so-called "predatory journals"), contributing to an industry valued at approximately $20 billion USD. Alongside the annual publication of over 7 million papers (estimated for 2023), concerns are mounting about flawed, incorrect, or fabricated data. The recent introduction of tools like ChatGPT has further elevated ethical concerns related to irregularities, errors, falsification in published papers to a new level. This work aims to highlight the major concerns regarding how the policies of many pay-to-publish journals harm the integrity of real science. The insights presented are based on the author's personal experiences and observations over 15 years as a referee for numerous journals. Meanwhile, the metric of "number of published papers per year" and "profit margins" seem to be the only "valuable" aspects of modern "science".

Development and publication of a multilingual chemical dictionary: A collaborative approach to terminology standardization

2024-11-27T02:39:36-08:00

The Chemical Dictionary, a collaborative effort by the Lexicographic Centre "Georgi Stardelov" at the Macedonian Academy of Sciences and Arts and Society of Chemists and Technologists of Macedonia, is a significant contribution to the standardization and accessibility of chemical terminology. The dictionary comprises 3,743 entries, each featuring a lemma, a concise definition, translation equivalents in four languages, and, in some cases, illustrative content. This multilingual and multidisciplinary approach addresses the growing need for uniformity in chemical language across educational, research, and professional contexts.

Published in two volumes of approximately 500 pages each, the dictionary adheres to international standards, including IUPAC (International Union of Pure and Applied Chemistry) nomenclature, ensuring its global relevance and accuracy. Its development involved extensive efforts from a multidisciplinary team of chemists, terminologists, and linguists who collaborated extensively from 2019 to 2024. The rigorous process included terminology extraction, definition refinement, and linguistic harmonization.

In addition to the print edition, the dictionary will be available online at https://term.manu.edu.mk/chemistry, utilizing the Lexonomy platform. This digital version offers advanced search capabilities, cross-referencing, and multilingual navigation, making it an indispensable resource for educators, researchers, and students.

Mechanochemical synthesis and solid-state characterization of molecular salts of pyridoxine: Vibrational spectroscopic and thermal consideration

2024-11-05T22:56:20-08:00

Crystal engineering of multicomponent crystals offers opportunities for both generic active pharmaceutical ingredients (APIs) and innovative APIs (under patent protection) to be noncovalently bound with a wide range of organic compounds, forming new solid phases such as salts or cocrystals. These multicomponent crystals can enhance the physicochemical properties, processibility, and bioavailability of the APIs. The purpose of this research is to correlate vibrational (FTIR and Raman) spectroscopy studies with the thermal behavior of new molecular salts of the drug model pyridoxine (PN), using salt formers from the group of hydroxybenzoic acid derivatives known for their potent antioxidant activity. The coformers include syringic acid (SA) and ferulic acid (FA), synthesized through eco-friendly mechanochemical methods by treating bulk powders of their stoichiometric mixture with PN. The assigned vibrational modes and thermal behaviors of the pyridoxonium syringate (PN/SA) and pyridoxonium ferulate (PN/FA∙H₂O) reveal the protonation of the pyridoxine N-atom in both salts structures. This protonation results in structural alterations in the crystal packing of the counterions, which exhibit unique spectral fingerprints and thermal profiles compared to the starting compounds.

Synthesis, single crystal structure, and Hirshfeld surface of (E)-N'-(2-hydroxybenzylidene)-2-((3- (trifluoromethyl)phenyl)amino)benzohydrazide

2024-08-05T02:07:47-07:00

A hydrazide-hydrazone derivative, (E)-N'-(2-hydroxybenzylidene)-2-((3-(trifluoromethyl)phenyl) amino)benzohydrazide, was synthesized and characterized using various spectroscopic techniques such as FTIR, ¹H-NMR and ¹³C-NMR spectroscopy, and X-ray diffraction. The compound crystallized in the monoclinic space group P2/n, with lattice parameters: a = 21.0586(8) Å, b = 8.1969(3) Å, c = 21.6475(10) Å, and β = 92.886(2)°.

Within a single crystal cell, two crystallographically independent asymmetric molecules are present. These molecules are chemically identical but display a non-planar geometric molecular structure. The crystal structure was stabilized by C–H⋯O and C–H⋯N hydrogen bonds, which facilitate intermolecular interactions that form a three-dimensional network. The presence of effective hydrogen bond donors and acceptors contribute to the formation of a tightly interconnected three-dimensional structure. Additionally, Hirshfeld surface analysis was conducted to examine potential hydrogen bonding and spatial arrangement of atoms. This analysis quantified hydrogen bond interaction and identified atoms likely to participate in such interactions. Alongside stabilization by strong hydrogen bonds, π⋯π interactions significantly influence the packing arrangement, with interactions among the phenyl rings observable through shape index and curvedness diagrams.

Preparation, characterization, and use of trimethoxy[3-(methylamino)propyl]silane functionalized SBA-15 for Congo Red adsorption

2024-11-19T22:04:23-08:00

Mesoporous materials have a broad range of applications in industry, and one of which is their potential use in adsorptive separations. This research investigates the use of a secondary amine-functionalized SBA-15 for the separation of a diazo dye, Congo Red (CR), from aqueous solutions. The synthesized SBA-15 was modified with trimethoxy[3-(methylamino)propyl] silane by a post-grafting method. The produced material was characterized using X-ray diffraction, N₂ physisorption, scanning electron microscopy, and transmission electron microscopy. The hexagonal mesostructure was preserved after functionalization; however, the specific surface area, pore diameter, and total pore volume of SBA-15 silica decreased. The adsorption of the diazo dye reached equilibrium by 50 minutes, and the data followed pseudo-second-order kinetics. While the yield increased with rising dosage and temperature, it decreased with CR concentration. The maximum adsorption capacity of functionalized SBA-15 (F-SBA-15) for CR uptake was found to be 211.07 mg/g. Thermodynamic data and parameters indicated the potential combination of physical and chemical interactions occurring during the adsorption process. The separation was endothermic and non-spontaneous; the equilibrium data fitted to the Freundlich adsorption isotherm at all tested temperatures. This study demonstrates that the secondary amine-functionalized SBA-15 can be used for the elimination of a toxic anionic diazo dye from aqueous solutions.

Novel treatment for dye decolorization using a microreactor system and Fenton's reagent

2024-06-19T03:08:20-07:00

Wastewater treatments in the textile industry faces many challenges, particularly due to the residues of used dyes, which are pollutants characterized by high chemical stability. One promising technology for addressing the issue is an advanced oxidation process (AOP), often utilizing Fenton's reagent as the oxidizing component. This study focuses on the degradation of the anthraquinone dye Acid Violet 109 using Fenton's reagent in a microfluidic reactor. The microreactor system consists of plunger pump units, a mixer, and a polytetrafluoroethylene (PTFE) tube. The influences of various process parameters have been analyzed, including the concentration of Fe²⁺, microreactor characteristics, the Fe²⁺/H₂O₂ molar ratio, and the total flow rate of the reaction mixture. The results show that treatment with Fenton's reagent is successful, with efficiencies between 82 and 99 %.

Anodic and cathodic components of currents of quasireversible electrode reactions on rotating disk electrodes under steady state conditions

2024-11-13T22:06:48-08:00

In a rotating disk electrode setup at constant potential, the current of a simple redox reaction becomes time-independent under steady-state conditions. This steady-state current can be expressed as a sum of two components, according to Butler-Volmer kinetics. While these components cannot be measured experimentally, they can be calculated using simple formulae based on the formal potential of the electrode reaction, which can be determined from the potential of zero current on the steady-state current-potential curve. The components can then be used to measure the transfer coefficients of quasireversible electrode reactions.

Assessment of volatile organic compounds in indoor environments across North Macedonia and Kosovo using passive sampling

2024-10-31T08:55:44-07:00

Humans are exposed to various volatile organic compounds (VOCs) through ingestion, inhalation, or skin contact, potentially leading to adverse health consequences. In this study, the distribution of vari-ous VOCs in indoor air in North Macedonia and Kosovo was investigated for the first time. From March to December 2023, the monthly relative abundance of VOCs was monitored using Radiello® pas-sive/diffusive samplers, followed by gas chromatography mass spectrometry (GC MS) analysis.
A total of 60 samples were collected from 17 sites, where over 70 individual VOCs belonging to several classes were identified. Benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds were the most abundant in the chemical stockroom, contributing up to 77.84 % of the total VOC relative abun-dance. In the printing store/workplace, alkylbenzenes were predominant, comprising 69.72 %. Alcohols and ethers were primarily detected in the coffee shop, whereas organosiloxanes were dominant in the hair salon, accounting for 33.87 % and 54.46 % of the total VOCs, respectively. Terpenes were a significant component in the meat factory, representing 65.78 % of the total VOCs, while hydrocarbons were most prevalent in the oil & lubricants store, accounting for 58.23%. Halogenated compounds were primarily found in the superstore, constituting 20.42 % of total VOCs. The VOC composition results indicate that their presence in indoor environments may pose both acute and chronic health risks.

Oxidation of HF with KMnO4 and possible misconceptions about HF

2024-07-23T01:35:30-07:00

Is hydrogen fluoride or its aqueous solution really incompatible with KMnO₄? If so, in what respect (meaning why)? This contribution seeks to answer the previous question that was posed some 20 years ago on the pages of the Journal of Chemical Education. The previous conclusion was that KMnO₄ cannot oxidize fluoride anions to elemental fluorine. However, this does not prevent the possibility of another type of reaction occurring between HF and KMnO₄.

In brief, the reaction of HF(aq) and KMnO₄(s) cannot occur with concentrated HF(aq), where w(HF) ≈ 0.4. However, the reaction of liquefied hydrogen fluoride, HF(l) and KMnO₄(s) appears to produce Mn₂O₇(l), which is explosive even at moderate temperatures. The same applies to aqueous solutions of HF where w(HF) ≥ 0.6. In this contribution, some details are further explained and the spreading of some misconceptions is, hopefully, hampered.

In addition, some authors described HF as a "flammable and explosive" substance, which is even worse than claiming that "water is flammable and explosive".