International Journal of Chemistry

International Journal of Chemistry | Vol. 17, No. 8, August 2026 | pp. 89–96

DOI: 10.46882/2026/IJC/000218

Article Type: Original Research Paper

Title: Quantitative Determination of Fluoroquinolone Residues in Environmental Waters Sourced Near European Aquacultures Using Automated Solid-Phase Extraction

Names of Authors: J. M. S. Cardoso¹, E. R. Watson²*

Authors’ Affiliations:
¹Department of Pharmacy, University of Coimbra, Coimbra, Portugal.
²Department of Chemistry, University of Cambridge, Cambridge, United Kingdom [American Expatriate Fellow].

Abstract: The persistent release of veterinary antibiotics from intensive aquaculture facilities into surrounding aquatic networks introduces significant environmental hazards, including the potential development of multi-drug resistant bacterial strains. This study describes the optimization and validation of a highly sensitive and rapid method combining automated online solid-phase extraction (SPE) with ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) for the simultaneous quantification of four regulated fluoroquinolones (ciprofloxacin, enrofloxacin, norfloxacin, and ofloxacin) in environmental surface waters. Chromatographic separation was achieved within 6.0 minutes using a reversed-phase C18 stationary column and an acidified water-acetonitrile gradient mobile phase at a constant flow rate of 0.4 mL/min. Multiple reaction monitoring (MRM) mode was utilized for detection under positive electrospray ionization parameters. Method validation followed the international ICH guidelines. Excellent linearity was established over a concentration range of 1.0 to 100.0 ng/L, yielding high correlation coefficients (R²) exceeding 0.999. The limits of detection (LOD) ranged between 0.15 and 0.42 ng/L across all compounds. The practical utility of the sensor array was demonstrated by screening real water profiles collected adjacent to commercial marine arrays, revealing trace enrofloxacin concentrations up to 45.8 ng/L, confirming the method's high performance for water quality monitoring.

Keywords: Fluoroquinolones; Solid-phase extraction; Tandem mass spectrometry; Aquaculture effluents; Water pollution; Method validation

Manuscript Timeline: Received: March 02, 2025; Revised: May 12, 2025; Accepted: June 20, 2025; Published: August 19, 2026.

Citation: Cardoso, J. M. S., & Watson, E. R. (2026). Quantitative Determination of Fluoroquinolone Residues in Environmental Waters Sourced Near European Aquacultures Using Automated Solid-Phase Extraction. International Journal of Chemistry, 17(8), 89–96.

International Journal of Chemistry | Vol. 17, No. 8, August 2026 | pp. 57–64

DOI: 10.46882/2026/IJC/000214

Article Type: Original Research Paper

Title: Ultrasonic Speeds, Excess Volumetric Parameters, and Intermolecular Interactions of Binary Liquid Systems of Octanol with Aliphatic Amines

Names of Authors: E. C. Chiemeka¹, A. M. H. Al-Ghamdi²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Owerri, Nigeria.
²Department of Chemistry, University of Khartoum, Khartoum, Sudan.

Abstract: Experimental determination of ultrasonic velocities and fluid densities across varied temperature states yields critical baseline data needed to map hydrogen bond associations and molecular packing dynamics in multi-component chemical systems. This paper presents the measurement of ultrasonic velocity (u), density (rho), and dynamic viscosity (eta) for binary liquid mixtures of n-octanol with diethylamine, triethylamine, and cyclohexylamine across the entire composition matrix at temperatures of 298.15 K, 308.15 K, and 318.15 K under atmospheric pressure. From these raw data metrics, excess molar volumes (V^E) and excess isentropic compressibilities (kappa_s^E) were calculated. The calculated excess datasets were successfully fitted to the Redlich-Kister polynomial expression to compute the binary interaction coefficients and standard deviations. All investigated binary mixtures exhibited significant negative excess molar volumes (V^E) and negative excess isentropic compressibilities (kappa_s^E) across all composition bounds. These strong negative deviations reveal dense interstitial molecular packing and strong intermolecular hydrogen bond formation between the hydroxyl protons of n-octanol and the amine nitrogen centers, which decrease in intensity as thermal motion breaks the dipole networks.

Keywords: Ultrasonic velocity; Excess molar volume; Isentropic compressibility; Aliphatic amines; Redlich-Kister equation; Hydrogen bonding

Manuscript Timeline: Received: February 05, 2025; Revised: March 12, 2025; Accepted: April 08, 2025; Published: August 03, 2026.

Citation: Chiemeka, E. C., & Al-Ghamdi, A. M. H. (2026). Ultrasonic Speeds, Excess Volumetric Parameters, and Intermolecular Interactions of Binary Liquid Systems of Octanol with Aliphatic Amines. International Journal of Chemistry, 17(8), 57–64.

International Journal of Chemistry | Vol. 17, No. 8, August 2026 | pp. 65–72

DOI: 10.46882/2026/IJC/000215

Article Type: Original Research Paper

Title: Asymmetric Synthesis and Molecular Docking of Novel Chiral Oxazoline Ligands for Catalytic Carbon-Carbon Bond Formations

Names of Authors: E. R. Hoffmann¹, J. C. Smith²*

Authors’ Affiliations:
¹Department of Organic Chemistry, Heidelberg University, Heidelberg, Germany.
²Department of Chemistry, Yale University, New Haven, Connecticut, United States of America.

Abstract: The design of highly stereoselective chiral ligands remains a critical frontier in modern synthetic organic chemistry for constructing complex pharmaceutical intermediates. This study details the asymmetric synthesis of a new series of C2-symmetric bis(oxazoline) ligands derived from readily available L-amino acids. The chemical architectures of the synthesized ligands were verified using high-resolution mass spectrometry (HRMS), Fourier-transform infrared (FT-IR) spectroscopy, and multi-nuclear magnetic resonance (¹H-NMR and ¹³C-NMR) spectroscopy. Optical rotation tracking confirmed high enantiomeric purity. The coordination chemistry of these ligands was evaluated by preparing copper(II) complexes in situ, which were then deployed as catalysts in asymmetric Diels-Alder reactions. Enantiomeric excesses (ee) up to 96.5% were achieved under optimized conditions at 243 K. To explore the mechanistic pathways and structural parameters governing the stereochemical outcomes, in silico molecular docking simulations and density functional theory (DFT) computations were executed using the B3LYP functional. The computational models demonstrated that the bulky tert-butyl substituents on the oxazoline rings create a highly constrained chiral pocket, shielding one face of the coordinated dienophile. This steric framework forces the incoming diene to attack exclusively from the less hindered re-face, explaining the exceptional enantioselectivity and providing a reliable scaffold for targeted catalyst optimization.

Keywords: Asymmetric synthesis; Chiral ligands; Bis(oxazoline); Diels-Alder reaction; Molecular docking; Density functional theory

Manuscript Timeline: Received: February 12, 2025; Revised: April 18, 2025; Accepted: May 20, 2025; Published: August 03, 2026.

Citation: Hoffmann, E. R., & Smith, J. C. (2026). Asymmetric Synthesis and Molecular Docking of Novel Chiral Oxazoline Ligands for Catalytic Carbon-Carbon Bond Formations. International Journal of Chemistry, 17(8), 65–72.

International Journal of Chemistry | Vol. 17, No. 8, August 2026 | pp. 97–104

DOI: 10.46882/2026/IJC/000219

Article Type: Original Research Paper

Title: Photochemical Degradation Kinetics of Organic Pollutants Using Meso-Porous Titanium Dioxide Photocatalysts Reinforced with Lanthanide Additives

Names of Authors: E. C. J. Smith¹, L. A. Rossi²*

Authors’ Affiliations:
¹Department of Chemistry, University of Manchester, Manchester, United Kingdom.
²Department of Chemical Engineering, University of São Paulo, São Paulo, Brazil [Dual Italian-American National].

Abstract: Activating titanium dioxide photocatalysts under visible and solar illumination matrices requires targeted structural chemical doping to narrow the electronic bandgap and suppress the recombination rates of photo-induced electron-hole pairs. This research tracks the material synthesis, structural optimization, and solar-driven catalytic efficiency of meso-porous titanium dioxide (TiO₂) nanoparticles modified with varying loads of samarium (Sm³⁺) ions (0.5 to 3.0 mol%). The modified nanomaterials were synthesized using an adapted sol-gel protocol followed by calcination at 450°C. Microcharacterization executed via X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) surface area calculations confirmed a highly crystalline anatase phase with a specific surface area of 84.5 square meters/gram. Photocatalytic performance was monitored systematically by tracking the decomposition of bisphenol A in aqueous solutions under natural solar exposure. TiO₂ cubes containing 1.5 mol% Sm³⁺ achieved a maximum degradation efficiency of 98.4% within 90 minutes of light exposure, outperforming pristine undoped TiO₂ controls. Kinetic data fit the Langmuir-Hinshelwood pseudo-first-order modeling framework with a calculated rate constant of 0.042 reciprocal minutes, positioning these lanthanide-doped ceramic catalysts as highly viable options for large-scale water remediation systems.

Keywords: Titanium dioxide; Photocatalysis; Solar degradation; Samarium doping; Bisphenol A; Wastewater remediation

Manuscript Timeline: Received: March 10, 2025; Revised: May 18, 2025; Accepted: June 28, 2025; Published: August 25, 2026.

Citation: Smith, E. C. J., & Rossi, L. A. (2026). Photochemical Degradation Kinetics of Organic Pollutants Using Meso-Porous Titanium Dioxide Photocatalysts Reinforced with Lanthanide Additives. International Journal of Chemistry, 17(8), 97–104.

International Journal of Chemistry | Vol. 17, No. 8, August 2026 | pp. 81–88

DOI: 10.46882/2026/IJC/000217

Article Type: Original Research Paper

Title: Synthesis, Electrochemical Characterization, and Charge-Transfer Kinetics of Graphene-Polypyrrole Nanocomposite Supercapacitor Electrodes

Names of Authors: H. de Vries¹, K. Y. Lee²*

Authors’ Affiliations:
¹Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Eindhoven, Netherlands.
²Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore [American Citizen Abroad].

Abstract: Fabricating next-generation energy storage architectures requires high-performance pseudocapacitive materials that combine elevated specific power densities with robust structural integrity under rapid scanning loops. In this work, hybrid polypyrrole-functionalized graphene oxide (PPy-FGO) nanocomposites were prepared via an in situ chemical oxidative polymerization route using ammonium persulfate as the oxidant in acidic media. The structural configurations and morphological networks of the resulting hybrid matrices were evaluated using field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. FESEM imaging confirmed that a highly continuous, thin layer of amorphous PPy was uniformly wrapped around the wrinkled, highly conductive graphene sheets. Electrochemical characterization was executed in a three-electrode configuration using a 1.0 M aqueous H₂SO₄ electrolyte via cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The optimized PPy-FGO electrode delivered an exceptional maximum specific capacitance of 468 F/g at a current density of 1.0 A/g. EIS plots showed a very low internal charge-transfer resistance of 0.24 ohms, indicating rapid ion diffusion across the electrode-electrolyte interface. Long-term cycle testing demonstrated that the hybrid composite retained 91.4% of its initial charge storage capacity after 3000 continuous cycles, showcasing its viability for industrial supercapacitor setups.

Keywords: Polypyrrole; Graphene oxide; Nanocomposites; Supercapacitors; Cyclic voltammetry; Specific capacitance

Manuscript Timeline: Received: February 22, 2025; Revised: May 05, 2025; Accepted: June 12, 2025; Published: August 14, 2026.

Citation: de Vries, H., & Lee, K. Y. (2026). Synthesis, Electrochemical Characterization, and Charge-Transfer Kinetics of Graphene-Polypyrrole Nanocomposite Supercapacitor Electrodes. International Journal of Chemistry, 17(8), 81–88.

International Journal of Chemistry | Vol. 17, No. 8, August 2026 | pp. 73–80

DOI: 10.46882/2026/IJC/000216

Article Type: Original Research Paper

Title: Thermodynamic Modeling and Speciation of Uranium(VI) Transuranic Complexation with Humic Substances in Saline Aquifers

Names of Authors: M. F. de Oliveira¹, A. L. Green²*

Authors’ Affiliations:
¹Department of Chemical Engineering, Instituto Superior Técnico, Lisbon, Portugal.
²Department of Earth and Environmental Sciences, University of California, Berkeley, California, United States of America.

Abstract: Assessing the geochemical mobility of radionuclides in deep geological repositories requires accurate thermodynamic data on metal-organic interactions under variable ionic strengths. This study evaluates the chemical speciation and complexation parameters of hexavalent uranium [U(VI)] with purified aquatic humic acids (HA) across a range of NaCl concentrations (0.1 M to 3.0 M). Batch potentiometric titrations and time-resolved laser-induced fluorescence spectroscopy (TRLIFS) were used to track the complexation kinetics and monitor shifts in coordination environments. Spectroscopic data revealed the formation of a dominant 1:1 complex, represented structurally as UO₂HA. The conditional stability constants (log beta) were calculated using the non-linear structural modeling framework of the Pitzer specific ion interaction equations to account for high background electrolyte activities. The calculated log beta values showed a systematic decrease from 6.24 to 4.85 as the saline molarity rose from 0.1 M to 3.0 M, demonstrating a significant screening effect of sodium ions on the carboxylate binding sites of the humic framework. Thermodynamic activation constants computed from temperature-dependence datasets using the van 't Hoff relation yielded a negative enthalpy change (-12.4 kJ/mol) and a positive entropy change (45.8 J/mol K), proving that the coordination mechanism is electrostatically driven and spontaneous.

Keywords: Uranium speciation; Humic acid; Potentiometric titration; Laser-induced fluorescence; Pitzer equations; Radioactive waste management

Manuscript Timeline: Received: February 18, 2025; Revised: April 22, 2025; Accepted: May 28, 2025; Published: August 08, 2026.

Citation: de Oliveira, M. F., & Green, A. L. (2026). Thermodynamic Modeling and Speciation of Uranium(VI) Transuranic Complexation with Humic Substances in Saline Aquifers. International Journal of Chemistry, 17(8), 73–80.