International Journal of Chemistry

International Journal of Chemistry | Vol. 9, No. 2, February 2018 | pp. 9–16

DOI: 10.46882/2018/IJC/000113

Article Type: Original Research Paper

Title: Isolation, Kinetic Modeling, and Structural Characterization of Thermophilic Amylases Sourced from Oil Mill Effluent Soils

Names of Authors: C. N. Nwosu¹, T. H. Sato²*

Authors’ Affiliations:
¹Department of Biochemistry, Nnamdi Azikiwe University, Awka, Nigeria.
²Department of Biomolecular Engineering, Tokyo Institute of Technology, Tokyo, Japan.

Abstract: The industrial hydrolysis of starch into fermentable sugars requires robust amylolytic enzymes that can resist thermal denaturation during high-temperature operations. This study details the isolation, microstructural profiling, and kinetic optimization of high-yielding alpha-amylase complexes produced by a thermophilic fungal strain sourced from palm oil mill effluent dumpsites. enrichment culturing was executed in starch-infused Mandels' media at 50°C, isolating a dominant strain identified via internal transcribed spacer (ITS) rRNA gene sequencing as Aspergillus nidulans strain POME-A2. Response surface methodology optimized solid-state fermentation yields using wheat bran matrices. Maximum alpha-amylase activity (48.5 U/mL) was achieved at an incubation temperature of 50°C, an initial substrate pH of 6.5, and a fermentation period of 96 hours. Biochemical characterization showed that the crude enzyme complex retained over 85% of its initial catalytic activity across a temperature range of 45 to 65°C and a pH stability window of 5.5 to 7.5 for 24 hours. The high thermal stability of this enzyme system, along with its independence from calcium ions, makes it a viable candidate for bio-refinery industrial operations.

Keywords: Alpha-amylase; Aspergillus nidulans; Solid-state fermentation; Thermal stability; Kinetic optimization; Starch saccharification

Manuscript Timeline: Received: November 10, 2016; Revised: December 18, 2016; Accepted: January 14, 2017; Published: February 06, 2018.

Citation: Nwosu, C. N., & Sato, T. H. (2018). Isolation, Kinetic Modeling, and Structural Characterization of Thermophilic Amylases Sourced from Oil Mill Effluent Soils. International Journal of Chemistry, 9(2), 9–16.

International Journal of Chemistry | Vol. 9, No. 4, April 2018 | pp. 25–32

DOI: 10.46882/2018/IJC/000115

Article Type: Original Research Paper

Title: Spatial Analysis, Speciation, and Carcinogenic Risk Profiling of Nickel Formulations in Well Water Networks near Steel Mills

Names of Authors: T. H. Awotunde¹, R. M. Silva²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Agriculture, Abeokuta, Nigeria.
²Department of Environmental Chemistry, University of São Paulo, São Paulo, Brazil.

Abstract: Metallurgical industrial smelting operations discharge significant amounts of nickel-rich waste into surrounding environments, causing heavy metal leaching into shallow drinking water aquifers. This study monitors the spatial variations, chemical speciation, and carcinogenic health risk profiles of nickel compounds across twenty household wells positioned around an active steel mill. Water monitoring was carried out over consecutive wet and dry cycles. Total nickel levels and specific nickel fractions were quantified utilizing ion chromatography coupled with inductively coupled plasma mass spectrometry (IC-ICP-MS). Total nickel concentrations ranged from 10.5 to 138.4 μg/L, with 38% of monitored groundwater sites surpassing the strict WHO drinkable contaminant threshold of 70.0 μg/L. Speciation analysis showed that soluble nickel ions were the dominant species, accounting for up to 64.2% of the total metal burden profiles at down-gradient coordinates. Seasonal mapping confirmed elevated nickel mobilization during the rainy period, indicating rain-induced plume leaching. Chronic Daily Intake (CDI) projections and Lifetime Cancer Risk (LCR) indices for child consumption cohorts surpassed 1.8 in 10,000 near industrial boundaries, emphasizing an immediate public healthcare concern and a need for local membrane filtration arrays.

Keywords: Groundwater pollution; Nickel speciation; Ion chromatography; Metallurgical effluents; Cancer risk assessment; Heavy metals

Manuscript Timeline: Received: December 02, 2016; Revised: January 14, 2017; Accepted: February 10, 2017; Published: April 02, 2018.

Citation: Awotunde, T. H., & Silva, R. M. (2018). Spatial Analysis, Speciation, and Carcinogenic Risk Profiling of Nickel Formulations in Well Water Networks near Steel Mills. International Journal of Chemistry, 9(4), 25–32.

International Journal of Chemistry | Vol. 8, No. 6, June 2017 | pp. 41–48

DOI: 10.46882/2017/IJC/000105

Article Type: Original Research Paper

Title: Kinetic Studies and Mechanistic Pathway of the Chromic Acid Oxidation of L-Methionine in Aqueous Acidic Medium

Names of Authors: T. M. Usman¹, F. A. Al-Otaibi²*

Authors’ Affiliations:
¹Department of Chemistry, Bayero University, Kano, Nigeria.
²Department of Chemistry, King Abdulaziz University, Jeddah, Saudi Arabia.

Abstract: Investigating the kinetics of transition metal electron transfer processes involving sulfur-containing amino acids provides vital structural indicators required to map metabolic oxidation pathways. The oxidation of L-methionine by chromic acid (H₂CrO₄) was investigated spectrophotometrically in an aqueous perchloric acid medium at a constant ionic strength of 0.40 M (NaClO₄). The reaction progress was monitored under pseudo-first-order conditions by following the absorbance decay of Cr(VI) at its wavelength maximum of 350 nm. The empirical rate law showed a first-order dependence on [chromic acid] and a fractional-first-order dependence on [L-methionine]. The reaction rate increased with rising hydronium ion concentration, revealing an acid-catalyzed pathway governed by the active protonated oxidant species, [HCrO₃⁺]. Variations in the dielectric constant of the solvent medium produced significant kinetic shifts, confirming a rate-determining step involving two polar molecular species. Stoichiometric determinations confirmed that 3 moles of L-methionine consumed 2 moles of chromic acid, producing methionine sulfoxide and Cr(III) ions as the primary end products. Thermodynamic activation constants calculated from temperature-dependence datasets using the Eyring equation yielded an enthalpy of activation (delta H*) of 48.5 kJ/mol and an entropy of activation (delta S*) of -104.2 J/mol K, supporting an inner-sphere mechanism.

Keywords: Reaction kinetics; Spectrophotometry; Chromic acid oxidation; L-methionine; Activation parameters; Inner-sphere mechanism

Manuscript Timeline: Received: July 10, 2016; Revised: August 20, 2016; Accepted: September 15, 2016; Published: June 03, 2017.

Citation: Usman, T. M., & Al-Otaibi, F. A. (2017). Kinetic Studies and Mechanistic Pathway of the Chromic Acid Oxidation of L-Methionine in Aqueous Acidic Medium. International Journal of Chemistry, 8(6), 41–48.

International Journal of Chemistry | Vol. 8, No. 8, August 2017 | pp. 57–64

DOI: 10.46882/2017/IJC/000107

Article Type: Original Research Paper

Title: Green Corrosion Inhibition of Carbon Steel in Acidic Medium Using Fruit Extract of Solanum melongena

Names of Authors: M. A. Haruna¹, S. K. Bhattacharya²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Minna, Nigeria.
²Department of Chemistry, Indian Institute of Technology, Kharagpur, India.

Abstract: The utilization of toxic synthetic chemical inhibitors in industrial acid descaling operations creates substantial environmental and safety hazards, driving research into sustainable green alternatives. The corrosion mitigation performance of the aqueous fruit extract of Solanum melongena (SM-Extract) on carbon steel in 0.5 M H₂SO₄ was investigated via gravimetric weight loss and electrochemical test protocols. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements were recorded across varying inhibitor dosages (0.2 to 2.0 g/L) and system temperatures (303 to 333 K). Weight loss metrics revealed that protection efficiency increased with extract concentration, peaking at 91.4% at a dose of 2.0 g/L. Polarization diagrams established that SM-Extract functions as a mixed-type inhibitor, suppressing both anodic iron dissolution and cathodic hydrogen gas evolution pathways. EIS scans confirmed that charge-transfer resistance (Rct) increased with higher extract amounts, indicating the formation of a robust organic protective film on the steel face. The adsorption behavior of the bioactive compounds conformed to the Langmuir isotherm model, yielding a negative standard free energy of adsorption (delta G°ads = -20.8 kJ/mol), denoting a spontaneous physical adsorption mechanism driven by the presence of rich plant anthocyanins.

Keywords: Carbon steel; Corrosion inhibition; Solanum melongena; Electrochemical impedance spectroscopy; Polarization; Adsorption isotherm

Manuscript Timeline: Received: August 14, 2016; Revised: September 25, 2016; Accepted: October 15, 2016; Published: August 03, 2017.

Citation: Haruna, M. A., & Bhattacharya, S. K. (2017). Green Corrosion Inhibition of Carbon Steel in Acidic Medium Using Fruit Extract of Solanum melongena. International Journal of Chemistry, 8(8), 57–64.

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. 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.