International Journal of Chemistry

International Journal of Chemistry | Vol. 8, No. 11, November 2017 | pp. 81–88

DOI: 10.46882/2017/IJC/000110

Article Type: Original Research Paper

Title: Thermodynamic Modeling, Desorption Kinetics, and Multilayer Adsorption of Acid Blue 25 Dye onto Modified Smectite Clay

Names of Authors: A. D. Yusuf¹, M. A. Al-Dosari²*

Authors’ Affiliations:
¹Department of Industrial Chemistry, Federal University of Technology, Yola, Nigeria.
²Department of Chemistry, Qatar University, Doha, Qatar.

Abstract: The release of highly stable anionic anthraquinone dyes like Acid Blue 25 from textile finishing plants causes significant environmental and toxicity hazards in surface aquatic resources. This study examines the adsorptive uptake performance of a surfactant-modified smectite clay (SMS) prepared via chemical functionalization with hexadecyltrimethylammonium bromide (HDTMA-Br). The structural parameters of raw and modified clays were characterized using X-ray diffraction (XRD) and FT-IR spectroscopy. Adsorption operations were conducted via batch runs, monitoring changes in contact time, solution pH, initial dye loading concentrations, and system temperatures. The equilibrium datasets fit closely with the Freundlich isotherm model, demonstrating successful multilayer dye attachment onto the hydrophobic surfactant bilayers. Kinetic parameters matched the intra-particle diffusion expressions alongside a pseudo-second-order mechanism, showing that chemisorption reactions controlled the mass transfer rates. Thermodynamic constants showed that the adsorption process was endothermic (delta H° = 21.4 kJ/mol) and caused an increase in system randomness at the solid-solution interface (delta S° = 72.5 J/mol K). Negative values of Gibbs free energy (delta G°) spanning from -2.1 to -5.5 kJ/mol across the 298 to 328 K range confirmed process spontaneity, positioning SMS as an affordable material for industrial dye wastewater treatment.

Keywords: Smectite clay; Surfactant modification; Acid blue 25; Adsorption isotherm; Chemisorption; Thermodynamic parameters

Manuscript Timeline: Received: October 02, 2016; Revised: November 15, 2016; Accepted: December 04, 2016; Published: November 09, 2017.

Citation: Yusuf, A. D., & Al-Dosari, M. A. (2017). Thermodynamic Modeling, Desorption Kinetics, and Multilayer Adsorption of Acid Blue 25 Dye onto Modified Smectite Clay. International Journal of Chemistry, 8(11), 81–88.

International Journal of Chemistry | Vol. 8, No. 10, October 2017 | pp. 73–80

DOI: 10.46882/2017/IJC/000109

Article Type: Original Research Paper

Title: Synthesis, Molecular Docking, and In Vitro Enzymatic Evaluation of Novel Indole-Linked Chalcone Derivatives

Names of Authors: O. M. Kolawole¹, E. C. J. Smith²*

Authors’ Affiliations:
¹Department of Chemistry, Obafemi Awolowo University, Ile-Ife, Nigeria.
²Department of Chemistry, University of Manchester, Manchester, United Kingdom.

Abstract: Inhibiting acetylcholinesterase (AChE) represents a vital clinical strategy for managing Alzheimer's disease by maintaining systemic acetylcholine neurotransmitter levels in brain tissue. In this work, five novel indole-linked chalcone derivatives were synthesized via Claisen-Schmidt condensation of indole-3-carboxaldehyde with various substituted acetophenones in the presence of potassium hydroxide catalysts. The molecular structures of the synthesized targets were verified using elemental analysis, FT-IR, and ¹H-NMR spectroscopy. In vitro AChE enzyme inhibition assays revealed that compound 3d, bearing a p-chlorosubstituent, possessed the highest inhibitory potency, showing an IC50 value of 7.8 μM compared to the donepezil clinical standard (IC50 = 2.1 μM). To investigate specific binding modes, in silico molecular docking simulations were run inside the catalytic active site of human AChE using AutoDock Vina software. The computational docking models demonstrated that the chalcone carbonyl forms stable hydrogen bonds with Gly121 and Ser203 residues. The indole ring extensions fit well into the peripheral anionic site, engaging in significant edge-to-face pi-pi stacking interactions with Trp286. These structural contacts stabilize the ligand-protein topology, explaining the low inhibition constants and presenting a potential scaffold for further antidementia drug design.

Keywords: Indole; Chalcones; Acetylcholinesterase; Enzyme inhibition; Molecular docking; Alzheimer's disease

Manuscript Timeline: Received: September 10, 2016; Revised: October 22, 2016; Accepted: November 15, 2016; Published: October 05, 2017.

Citation: Kolawole, O. M., & Smith, E. C. J. (2017). Synthesis, Molecular Docking, and In Vitro Enzymatic Evaluation of Novel Indole-Linked Chalcone Derivatives. International Journal of Chemistry, 8(10), 73–80.

International Journal of Chemistry | Vol. 8, No. 9, September 2017 | pp. 65–72

DOI: 10.46882/2017/IJC/000108

Article Type: Original Research Paper

Title: Development and Validation of an RP-HPLC Method for Quantitative Monitoring of Amoxicillin Formulations

Names of Authors: E. O. Effiong¹, L. A. S. dos Santos²*

Authors’ Affiliations:
¹Department of Chemistry, University of Uyo, Uyo, Nigeria.
²Department of Pharmacy, Federal University of Minas Gerais, Belo Horizonte, Brazil.

Abstract: Developing simple, automated, and accurate analytical methods is essential for routine quality monitoring and the detection of counterfeit beta-lactam antibiotics in commercial pharmacies. This paper describes the development and validation of a rapid Reversed-Phase High-Performance Liquid Chromatography (RP-HPLC) method for the quantitative determination of amoxicillin in capsule dosage forms. Separation was achieved using a C18 stationary phase column under an isocratic mobile phase composed of phosphate buffer (pH 4.0)-acetonitrile (85:15 v/v), at a flow rate of 1.0 mL/min. Eluent monitoring was executed spectrophotometrically at a wavelength maximum of 230 nm. Method validation parameters followed the International Council for Harmonisation (ICH) guidelines. Excellent linearity was established over a concentration range of 2.0 to 50.0 mg/L with a correlation coefficient (R²) of 0.999. The limit of detection (LOD) and limit of quantification (LOQ) were determined to be 0.06 mg/L and 0.18 mg/L, respectively. Precision assessments yielded relative standard deviations (RSD) below 1.4%. The validated method was successfully applied to screen six commercial amoxicillin brands, producing recovery percentages between 98.6% and 101.4% with no interference from common excipients.

Keywords: RP-HPLC; Amoxicillin; Quantitative analysis; Method validation; Pharmaceuticals; Quality control

Manuscript Timeline: Received: September 02, 2016; Revised: October 12, 2016; Accepted: November 05, 2016; Published: September 09, 2017.

Citation: Effiong, E. O., & dos Santos, L. A. S. (2017). Development and Validation of an RP-HPLC Method for Quantitative Monitoring of Amoxicillin Formulations. International Journal of Chemistry, 8(9), 65–72.

International Journal of Chemistry | Vol. 8, No. 2, February 2017 | pp. 9–16

DOI: 10.46882/2017/IJC/000101

Article Type: Original Research Paper

Title: Synthesis, Luminescent Properties, and Fluorimetric Detection of Nitroaromatic Explosives Using Novel Terbium(III) β-Diketone Complexes

Names of Authors: A. O. Balogun¹, J. E. Kim²*

Authors’ Affiliations:
¹Department of Chemistry, University of Ilorin, Ilorin, Nigeria.
²Department of Chemistry, Seoul National University, Seoul, South Korea.

Abstract: Rare-earth coordination materials displaying highly sensitive photoluminescent behaviors are increasingly sought for chemical sensor fabrications due to their sharp emission bands and high signal-to-noise ratios. This study reports the synthesis, material characterization, and analytical sensor optimization of a novel terbium(III) complex using 2-thenoyltrifluoroacetone and 1,10-phenanthroline ligands. Structural configurations were verified using elemental analysis, molar conductance, and Fourier-transform infrared (FT-IR) spectroscopy. Analytical calculations confirmed a 1:3:1 metal-to-ligand stoichiometric coordination pattern, conforming to the formula [Tb(TTA)₃(phen)]. Molar conductivity tests in acetonitrile confirmed a completely non-electrolytic layout. Photoluminescence scanning at room temperature showed intense green monochromatic emission peaks at 545 nm, corresponding to the characteristic ⁵D₄ to ⁷F₅ electronic transition of the central Tb(III) ion. The analytical potential of the complex as a fluorimetric sensor for trace nitroaromatic explosives was evaluated in aqueous media. The introduction of picric acid caused immediate, highly selective luminescence quenching of the green emission intensity. The fluorimetric quenching behavior followed the Stern-Volmer relationship with a high quenching constant (Ksv) of 4.5 x 10⁴ M⁻¹ and a low limit of detection (LOD) of 0.18 μM, pointing to a photoinduced electron transfer pathway.

Keywords: Terbium complexes; Rare earth elements; Photoluminescence; Fluorimetric sensor; Nitroaromatic explosives; Stern-Volmer relation

Manuscript Timeline: Received: May 12, 2016; Revised: June 25, 2016; Accepted: July 18, 2016; Published: February 04, 2017.

Citation: Balogun, A. O., & Kim, J. E. (2017). Synthesis, Luminescent Properties, and Fluorimetric Detection of Nitroaromatic Explosives Using Novel Terbium(III) β-Diketone Complexes. International Journal of Chemistry, 8(2), 9–16.

International Journal of Chemistry | Vol. 8, No. 12, December 2017 | pp. 89–96

DOI: 10.46882/2017/IJC/000111

Article Type: Original Research Paper

Title: Green Synthesis of Gold Nanoparticles Using Aqueous Leaf Extract of Alchornea cordifolia and Catalytic Reduction of Methylene Blue

Names of Authors: S. I. Musa¹, C. R. de Souza²*

Authors’ Affiliations:
¹Department of Chemistry, University of Jos, Jos, Nigeria.
²Department of Chemical Engineering, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.

Abstract: The biological synthesis of noble metal nanomaterials using tropical flora presents an eco-friendly and economically sustainable alternative to hazardous chemical reduction pathways. This study describes the green synthesis of stable gold nanoparticles (AuNPs) utilizing the aqueous leaf extract of Alchornea cordifolia as a powerful reducing and capping agent. The bioreduction process was monitored via UV-Vis spectrophotometry, which revealed a distinct surface plasmon resonance peak at 532 nm, confirming the nucleation of metallic gold. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses showed highly spherical nanoparticles with an average particle diameter of 15 nm. X-ray diffraction (XRD) patterns confirmed the face-centered cubic crystalline structure of the biosynthesized gold. Fourier-transform infrared (FT-IR) spectroscopy indicated that water-soluble polyphenols and flavonoids within the leaf matrix were responsible for capping and protecting the AuNPs against structural agglomeration. The catalytic efficiency of the synthesized AuNPs was evaluated by tracking the chemical reduction of methylene blue dye by sodium borohydride (NaBH₄) in an aqueous system. In the presence of the green catalyst, the reaction achieved 96.8% decolorization within 8 minutes. The dye degradation kinetics conformed tightly to the pseudo-first-order kinetic model with a rate constant of 0.295 min⁻¹, indicating excellent catalytic potential for textile wastewater treatment arrays.

Keywords: Gold nanoparticles; Green synthesis; Alchornea cordifolia; Biosynthesis; Heterogeneous catalysis; Methylene blue degradation

Manuscript Timeline: Received: October 12, 2016; Revised: November 24, 2016; Accepted: December 18, 2016; Published: December 04, 2017.

Citation: Musa, S. I., & de Souza, C. R. (2017). Green Synthesis of Gold Nanoparticles Using Aqueous Leaf Extract of Alchornea cordifolia and Catalytic Reduction of Methylene Blue. International Journal of Chemistry, 8(12), 89–96.

International Journal of Chemistry | Vol. 8, No. 3, March 2017 | pp. 17–24

DOI: 10.46882/2017/IJC/000102

Article Type: Original Research Paper

Title: Adsorptive Sequestration of Mercury(II) Ions from Simulated Saline Wastewater Using Thiolated Peppermint Waste

Names of Authors: E. N. Chidi¹, L. M. van der Westhuizen²*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, Nnamdi Azikiwe University, Awka, Nigeria.
²Department of Chemical Engineering, Stellenbosch University, Stellenbosch, South Africa.

Abstract: Industrial wastewater from chlorine-alkali facilities often contains high residual levels of highly toxic mercury(II) ions, requiring affordable and chemically stable biopolymer extraction networks. This paper evaluates the adsorptive performance of modified peppermint (Mentha piperita) waste prepared via chemical functionalization with thioglycolic acid (thiolation). The surface morphology and active site modifications of the matrix were examined through scanning electron microscopy (SEM) and FT-IR spectroscopy. The structural evaluations confirmed that thiolation successfully integrated sulfur-rich thiol (-SH) ligand centers onto the lignocellulosic biomass strands. Batch adsorption tests evaluated variables of baseline solution pH, contact period, adsorbent load, and initial metal concentrations. Maximum Hg(II) extraction occurred at an optimum pH of 5.5, using an equilibrium contact period of 60 minutes. The equilibrium distribution datasets matched closely with the Langmuir isotherm expressions, yielding a high maximum monolayer adsorption capacity of 74.45 mg/g at 298 K. Sorption kinetics conformed perfectly to a pseudo-second-order mechanism with high correlation coefficients (R² > 0.999), proving that strong chemical surface coordination controlled the phase transfer rates. Thermodynamic constants established that the process was spontaneous and endothermic, positioning thiolated biomass as a highly viable material for toxic water remediation.

Keywords: Peppermint waste; Chemical modification; Thiolation; Mercury removal; Sorption kinetics; Coordination chemistry

Manuscript Timeline: Received: June 02, 2016; Revised: July 15, 2016; Accepted: August 10, 2016; Published: March 08, 2017.

Citation: Chidi, E. N., & van der Westhuizen, L. M. (2017). Adsorptive Sequestration of Mercury(II) Ions from Simulated Saline Wastewater Using Thiolated Peppermint Waste. International Journal of Chemistry, 8(3), 17–24.