STUDIA CHEMIA - Issue no. 1 / 2023 - Table of contents

A zeolitic imidazolate framework ZIF-67 was synthesized by an eco-friendly solvothermal method, using ethanol as solvent at room temperature. The morphology and structure of obtained ZIF-67 were characterized by X-ray diffraction, scanning electron microscopy (SEM), nitrogen adsorption/desorption isotherm, energy dispersive spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FTIR). The ZIF-67 modified graphite paste electrode (ZIF-67-GPE) was prepared and used for the electrochemical detection of acetaminophen (AC). Cyclic voltammetry (CV) and square wave voltammetry (SWV) were employed to investigate the electrochemical behavior of AC at ZIF-67-GPE modified electrode. At the optimal working conditions, the limit of detection was 0.2 μM (S/N = 3) in the linear range of 2 - 10 μM AC. The good analytical parameters indicated its applicability for AC determination in real samples.

Keywords: Zeolitic imidazolate framework, graphite paste modified electrode, acetaminophen

The widespread use of paracetamol and non-steroidal antiinflammatory drugs (NSAIDs) make them increasingly present in environmental factors, especially in water. The aim of this work was to develop an accurate, precise and sensitive analytical procedure for the simultaneous determination of Paracetamol and four NSAIDs (Ketoprofen, Naproxen, Diclofenac, and Ibuprofen). To this aim, the extraction (liquid-liquid extraction, LLE, and solid-phase extraction, SPE) as well as the chromatographic (high-performance liquid chromatographyphotodiode array detector, HPLC-PDA, and gas chromatography-mass spectrometry in selected ion monitoring mode, GC-MS-SIM) techniques, in terms of the performances were compared. Different extraction solvents and types of cartridges at pH 3 of samples were tested for the extraction optimization. Low limits of detection and quantification at the μg/L level were achieved. The developed HPLC-PDA and GC-MS-SIM methods were applied to the analysis of selected pharmaceuticals in different wastewater samples.

Keywords: paracetamol and NSAIDs, solid-phase extraction, liquid-liquid extraction, GC-MS, HPLC-PDA

The aim of the current study was to investigate whether food intake alters the kinetics of dapaglliflozin, a modern anti-diabetic agent, after single-dose oral administration of a new 10 mg immediate release tablet. The evaluated formulation was developed and manufactured by Sun Pharmaceutical Industries Limited, India, and the studies were performed in healthy Caucasian subjects. The data obtained during the fasting and fed bioequivalence studies were analyzed to observe the influence of food on the bioavailability and disposition of the evaluated formulation. Although differences were observed between studies concerning some of the main parameters that describe dapagliflozin’s disposition (maximum plasma concentration – Cmax, and the time to reach it -Tmax), they were proved bioequivalent. The 90% confidence intervals for the evaluated parameters were within the accepted range of 80.00-125.00% for bioequivalence conclusion, therefore the treatments are bioequivalent (dapagliflozin with/without food) and interchangeable. Hence, dapagliflozin can be administered regardless of food intake in diabetic patients.

Keywords: dapagliflozin, kinetics, Caucasian volunteers, clinical trial, food intake

The effects of alternative pulsed electric fields on the esterification reactions between acetic acid and different alcohols were investigated in this paper. The aim of this study was the synthesis of some esters using a new and ecological method. Only acetic acid and different alcohols were used as raw materials and an alternative pulsed electric field as accelerator. Also, the enzymatic synthesis of esters was performed in order to draw a conclusion on the effectiveness of the new proposed method. Gas chromatography analysis showed that the esterification was considerably enhanced by an alternative pulsed electric field. The highest amounts of ester were obtained for n-propyl acetate, significantly higher than in the case of enzymatic synthesis. The synthesis of i-butyl and i-amyl acetate using the alternative pulsed electric field shows the formation of lower amounts of ester, probably due to the conformation of the molecule. Using raw materials of natural origin (acetic acid and alcohols obtained, for example, by fermentation) in the presence of an alternative pulsed electric field, natural esters are obtained and they can be used without restrictions in pharma, food, perfume or cosmetic industry.

Keywords: esterification reactions, pulsed electric field, enzymatic synthesis, food industry, natural esters

The electrical and molar conductivities of potassium iodide solutions in different concentrations of sunflower oil-DMF and corn oil-DMF solvents were measured at temperatures of 303.15, 308.15, 313.15, 318.15 and 323.15 K. The electrical and molar conductivity increased with an increase in temperature while an increase in the concentration of oil in the solvent had a decreasing effect. The electrical conductivity increased while the molar conductivity decreased with an increase in the concentration of potassium iodide in the solution. The limiting molar conductivities of the potassium iodide solution evaluated by the plots of the Debye-Huckel relation were used to determine the strength of ion-ion and ion-solvent interactions. The ion-ion interaction coefficient (A) varied irregularly with temperature while the ion-solvent interaction coefficient (B) increased with temperature in a pattern characteristic of structure-breaking electrolytes. The limiting molar conductivity of potassium iodide solutions obeyed the Arrhenius model of temperature dependence.

Keywords: Vegetable oil; Electrical conductivity; N, N-Dimethylformamide (DMF), Ion-ion interaction; Ion-solvent interaction

Schiff and azo-Schiff base derivatives were synthesized, identified and evaluated for their antimicrobial and antifungal activities against gram-positive bacteria, gram-negative bacteria and fungi such as Escherichia coli, Pseudomonas aureginosa, Staphylococcus aureus, Bacillus cereus, Salmonella typhimurium, Saccharomyces cerevisiae and Candida albicans. Chiral amides (2a-e) were synthesised by using D-Phenylglycine, L-Phenylalanine, L-valine, L-isoleucine and L-methionine. Experimental studies include the use of chiral amide derivatives (2a-e) of the five amino acids to synthesize the Schiff and azo-Schiff base derivatives of amides (3a-e, 4a-c and 4e). The structures of the compounds were determined by spectroscopic analyses (FTIR, 1H-NMR, 13C-NMR) and elemental analysis. Among the tested compounds, compound 3b and 3d were found to show the most potent inhibitory action against Gram positive and Gram negative bacteria.

Keywords: Schiff base, azo-Schiff base, amino acid, amide, biological activity

Two commercial stoneware pastes traditionally used to produce ceramic objects were evaluated. The objective was the comparative characterization of the pastes and to find the most suitable to obtain fine ceramic objects using the pottery wheel. Both ceramic pastes were characterized by X-ray powder diffraction (XRPD), particle size analyses (laser diffraction) and thermal analyses (thermogravimetry-TG, its derivative-DTG, and differential thermal analysis-DTA). The technological properties like linear drying and firing shrinkage, moisture content and plasticity were also determined. The results showed that both pastes have appropriate properties making them suitable for plastic shaping by pottery wheel. In addition, the stoneware paper clay paste is “greener” due to its content of cellulose fibers which can come even from recycled paper.

Keywords: traditional ceramics, commercial stoneware, XRPD, TG-DTG-DTA, drying and firing shrinkage, moisture content, plasticity, potter’s wheel

One of the challenges facing poultry farming is the safe and economical disposal of poultry litter (PL) waste. PL pyrolysis offers a solution and a commercial scale induction heated auger type reactor, was developed into an engineering solution through mathematical modelling, design, and construction. A 1 ton/day proof-of-concept plant was realized to validate laboratory scale experimental results, producing bio-oil, biochar, and gas at typical product yields of >50%, ~20% and <30% respectively. The pyrolysis plant was packaged into a standard ISO-container format, enabling complete fabrication and testing in a production line, whereafter it can be shipped to any remote location via road, rail, or sea freight, ready to operate by the turn of a key at arrival. With the addition of a heavy fuel oil (HFO) or gas-powered generator, the unit can operate self-sustainably as a stand-alone unit.

Keywords: Auger Reactor, Poultry Litter Pyrolysis, Waste to Energy, Circular Economy, End-of-Waste

The article reports the AMS (accelerator mass spectrometry) radiocarbon investigation of the historic Grand Baobab of Mahajanga. The largest African baobab of Madagascar exhibits a cluster structure, which consists of 6 fused ordinary stems and of 3 small binding stems. Two samples were collected from the largest stem and from a primary branch, out of which several tiny segments were extracted and dated by radiocarbon. The oldest dated sample segment had a radiocarbon date of 214 ± 17 BP, which corresponds to a calibrated age of 265 ± 25 calendar years. The dating results indicate that the Grand Baobab of Mahajanga is 275 ± 25 years old.

Keywords: AMS radiocarbon dating, Adansonia digitata, dendrochronology, Madagascar, age determination, multiple stems.

The aim of this study was to examine the antineurodegenerative, antimicrobial and antioxidant potential and to determine the total phenolics and total flavonoids of acetone extracts of selected mushrooms species (Suillus luteus, Leccinum aurantiacum, Agaricus xanthoderma and Tricholoma terreum) belonging to the genera Boletus and Agaricus. The content of phenolic components in the tested mushroom species varied in the total amount from 94.95 to 147.81 μg PE/mg extract, while the content of flavonoids varied in the range from 2.43 to 23.71 μg RE/mg extract. The tested acetone extracts showed acetylcholinesterase inhibition ranging from 11.49 to 17.46%. The strongest antimicrobial activity for the tested bacteria and fungi was shown by the species Agaricus xanthoderma. The antibacterial effect was stronger than the antifungal. Acetone extracts of the tested mushroom species showed moderate antioxidant activity. This study shows that the tested species of mushrooms possess different biological activity and that they can be used as a good source of natural agents are beneficial for human health.

Keywords: mushroom, biological activity, antioxidants

Of the medicinal plants’ cosmos, yarrow species (A. millefolium L. and A. wilhelmsii L.) are of the reputed species due to their phytochemical composition and thereby antioxidant and antibacterial activities. Owing to the high diversity in chemical composition and production of essential oil, the species deserves to be investigated more. In this context, wild yarrow plants were collected in Eastern Anatolia region (Van, Türkiye) and then the dried samples of the plants were subjected to hyd-rodistillation for essential oil extraction. In addition, the essential oils were assayed for their potential antioxidant and antibacterial activities. Gas Chromatography Mass Spectrometry (GC-MS) analysis revealed the presence of 1,8-cineole (75.19%), α-phellandrene (5.53%), P-eugenol (5.53%), camphor (5.45%), α-terpineol (2.09%), β-pinene (1.66%), camphene (1.20%), α-pinene(1.02%) from A. millefolium L. However, A. wilhelmsii was characterized with menthoglycol (35.84%), 1,8-cineole (34.04%), endo-borneol (9.93%), chrysanthenil acetate (4.76%), thymine (3.66%), terpinene-4-ol (2.33%), camphene (1.66%), and verbenole (1.53%). Regarding scavenging activities of the species, A. wilhelmsii exhibited better activity than A. millefolium, with a value of 6.5 mM and 4.2 mM Trolox equivalents (TEAC) respectively. With respect to the antibacterial activity against three gram-negative and three gram-positive bacteria, essential oils of both species were compared with standard antibiotic discs (ampicillin and ofloxacin).

Keywords: Achillea millefolium, Achillea wilhelmsii, Yarrow, Essential oils, Biological activity, GC-MS analysis.

In this study, the effects of three different extraction methods on the antioxidant capacity, phenolic component, volatile organic molecule, and amino acid contents in the leaves of the Moringa (Moringa oleifera Lam.) were compared. The amino acid contents were evaluated via liquid chromatography-diode array detection (HPLC-DAD) analysis. In gas chromatography-mass spectrometry (GC-MS) analysis, loliolide and phytol molecules were detected in moringa leaves. Gallic acid, chlorogenic acid, 4-hydroxybenzoic acid, acid, vanillic acid, p-coumaric acid, hesperidin, hyperoside, quercetin, kaempferol were found in high amounts in moringa leaves by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Tyrosine, glutamic acid, alanine, tryptophan, and L-theanine amino acids were determined by HPLC-DAD analysis. Microstructures images of three extracts were shown with Scanning Electron Microscope (SEM). Element content and mapping were demonstrated by Energy Dispersive X-ray Spectroscopy (EDX). It was found that the best extraction method is MDAE when compared to UBAE and HAE.

Keywords: Extraction, phenolic compound, amino acid, HPLC-DAD, LC-MS/MS, SEM-EDX.

This paper studies the thermodynamics of the adsorption of textile dye on clinoptilolite in order to estimate the potential of this natural material for decolorization. The adsorption of dye in the state of equilibrium in conditions of varying temperature, as well as different models of thermodynamic equilibrium, were analyzed. The most present mineral phase of the adsorbent is the mineral clinoptilolite with a mineral content of about 85% in the tuff. The natural adsorbent, clinoptilolite, originally from Serbia, was characterized by chemical analysis, and dominated by SiO2 (59.57%). The surface morphology was monitored by electron microscopy. In the research, the concentration of the textile cationic dye (10-110 g⋅dm-3) and the adsorption temperature (293-333 K) were varied, while the amount of clinoptilolite was constant (1 g). To characterize the equilibrium adsorption, the dye removed and the amount of adsorbed dye were calculated. In adsorption thermodynamics, several models have been studied to calculate the most important thermodynamic parameters, free energy change, enthalpy, and entropy change, depending on the choice of thermodynamic equilibrium constant. The activation energy and sticking probability were calculated using a modified Arrhenius–type equation.

Keywords: clinoptilolite, adsorption, textile cationic dye, thermodynamics, free energy change, enthalpy change, entropy change, activation energy

In this work it was studied the removal of copper ions from wastewater by adsorption on oak wood ash and the effect of the ash resulting from adsorption process as a soil amendment. The process variables such as pH, contact time and adsorbent dose were optimized for maximum Cu2+ removal. It was establishing the mathematical correlation between this factors and the metal ions removal efficiency using specific 3D software. Adsorption process is described by Freundlich isotherm and pseudo-first order kinetic model. The effect of the wood ash, previously used as adsorbent, as soil amendment was studied using barley crop, Hordeum vulgare L. The values of the specific parameters: germination percent, plant average length, biomass and relative growth rate proving the beneficial effect of the use of wood ash (resulted from the adsorption process) on plant growth.

Keywords: Cu²⁺ adsorption; Oak woods ash; Mathematical correlation; Equilibrum; Kinetics; Soil amendment.

The study examined the effect of dietary supplements of lead acetate (PbA) and/or aluminosilicates (zeolite and montmorillonite) on growth traits, relative organ weights, activity of liver enzymes and activity of enzymes of antioxidant protection and lipid peroxidation in liver, erythrocytes, pancreas and spleen of chickens. Weight gain, feed conversion ratio, relative weights of liver, pancreas and spleen and activity of antioxidative enzymes in pancreas and spleen were not influenced with dietary treatment. Dietary intake of PbA induces oxidative stress and promotes lipid peroxidation in liver and erythrocytes. Activities of liver enzymes (alkaline phosphatase, γ-glutamyltransferase and α-amylase) were influenced by PbA also. Aluminosilicates alone did not provoke any adverse effect and did not disturb normal biochemical and physiological homeostasis in broilers. The combined data showed that chickens fed aluminosilicates received significant protection against the effects of the PbA for most parameters measured.

Keywords: aluminosilicates; antioxidative enzymes; bentonite; chickens; erythrocytes; lead acetate; liver; montmorillonite

Sulfur has been used for a long time as a vulcanizing agent for polybutadiene and polyisoprene rubber. The presence of sulfur in the used crumb rubber powder reduces its dispersion in the bitumen and favors its separation from the colloidal structure of the bitumen. For this reason, it does not allow the use of this waste to modify the road bitumen. In this paper, the desulfurization of used crumb rubber is studied by reactive adsorption in the presence of metal oxide adsorbents in pulverized form. Metal oxide adsorbents were prepared based on Fe, Cu and a mixture of the two metal oxides with a bimodal particle size distribution and an average particle diameter between 500 and 800 nm, by the sol-gel precipitation method, in the presence of a Pluronic® surfactant. The morphology of the prepared adsorbents was investigated by Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM) and nitrogen porosimetry analyses (BET method). The desulfurization of crumb rubber experiments was carried out in a high-pressure Parr stainless steel reactor with electric heating and stirring in an inert gas atmosphere (nitrogen). The conversion in the desulfurization process of vulcanized rubber was influenced both by the size of the adsorbent particles and also by the nature of the adsorbent.

Keywords: crumb rubber, desulfurization, absorbents, sol-gel method, metallic oxides

As a result of environmental and economic concerns, anaerobic co-digestion process has gained increasing interest as a viable technology for both energy production and waste treatment. In this work, anaerobic co-digestion of agricultural residues (animal slurry and corn grains) and wastewater from a local brewery plant was studied using a laboratory-scale experimental installation. Multiple batch experiments (Tst1-Tst7) were carried out in which the influence of the substrate mixture ratio, the temperature and the purging of N2 of the reactor on the process was analyzed. Batch anaerobic-digestion experiments were performed at initial pH values between 7.5÷7.9 and at two temperature regimes (termophilic and mesophilic) and the substrates involved in the experiments were characterized using solid biofuels European Standard (EN 14774, EN 14775, EN 14918, EN 15297). The biogas was characterized by determining the CH4, CO2, and H2S fraction over time. The best results were obtained when nitrogen purging was used to minimize the exposure of the substrate mixture to oxygen at an operating temperature of 45°C and a volume ratio of animal slurry to wastewater of 3:1 and 150 g of corn grain. Higher operating temperature and N2 purging had a positive impact by increasing biogas production and decreasing the H2S fraction of the total produced gas.

Keywords: biogas production, agricultural residues, lab-scale experiments, N2 purging

Heat-cure denture base resins are the most used materials in denture fabrication for almost a hundred years, because of their favorable characteristics, but they also have some drawbacks that influence the durability and biocompatibility. Over time researchers tried to obtain improvements of the denture materials by adding different types of additives. Water sorption, solubility, and monomer release are among the most important acrylic resins characteristics that influence dentures’ durability and biocompatibility. The aim of the present study was to evaluate the effect of graphene silver nanoparticles addition to a commercial heat-curing acrylic resin processed through a fast-polymerization cycle on the water sorption, solubility, and monomer release.

Keywords: acrylic resin, water sorption, solubility, monomer release, graphene silver nanoparticles

A technological accident in a fertilizer production plant often results from the interaction between several hazards. Preliminary Hazard Analysis (PHA) being a general level, qualitative method, it is easily applicable for all types of operations and functions of a system. The objective of this paper is to demonstrate the importance of using PHA in the context of preventive and predictive maintenance, and to highlight the potential benefits of these strategies in mitigating the risks of potential accidents related to the granulation process of fertilizer grade AN. The results of the study show that the most dangerous scenarios identified, in terms of consequences, are potential explosions of AN due to friction and melting in case of rotative equipment failure, or auto-decomposition and explosion of AN due to contamination with organic substances. Since qualitative deterministic approaches are lacking in uncertainty and sensitivity analysis, their use should be completed by more complex quantitative analyses, in order to support efficient decision making for risk mitigation and balanced maintenance efforts.

Keywords: ammonium nitrate, granulation process, preliminary hazard analysis, predictive maintenance, preventive maintenance

Inverted bilayer and inverted bulk heterojunction OSCs were fabricated and investigated using D-A and A-D-A donors with bi[3,2-b]thienothiophene units and PC61BM or C70 acceptors. The cells were optimized by varying the donor/acceptor ratios, the thickness of the layers and the conditions for the spin-coating deposition of the active materials.

Keywords: organic solar cells, inverted bilayer structure, inverted bulk heterojunction, 2,2’-bi[3,2-b]thienothiophene donors

In this study, a comparative determination of the quality factors, chemical composition and antimicrobial activity for ozonated and non-ozonated olive, coconut and hemp oils was made. The following quality factors for non-ozonated and ozonated oils were determined: peroxide value, acidity value, iodine value and density. The composition of methyl esters of fatty acids and the final compounds resulting from the ozonation process of the studied vegetable oils was characterized by Gas-Chromatography-Mass Spectrometry (GC-MS). The oil samples showed varying degrees of antibacterial activity against selected pathogens. Ozonated oils act as a matrix capable of releasing active oxygen from ozonides, which have antimicrobial activity. Density, peroxide value and acid value increased in all ozonated oils, while iodine value decreased in all ozonated oils. The gas chromatography showed a change in the degree of unsaturation due to the ozonation process, such that: the total content of unsaturated compounds decreased by 24.58% in ozonated olive oil, by 37.88% in ozonated hemp oil and by 9.14% in ozonated coconut oil. The innovative aspect of the paper consists in the physico-chemical and chromatographic characterization of the ozonated hemp oil and the comparison of the antimicrobial activity of the studied oils.

Keywords: olive, coconut, hemp, ozonated oil, GC-MS, antimicrobial activity