International Journal of Chemistry

International Journal of Chemistry | Vol. 7, No. 6, June 2016 | pp. 41–48

DOI: 10.46882/2016/IJC/000093

Article Type: Original Research Paper

Title: Isolation, Structural Profiling, and Optimizing Kinetics of Amylolytic Complexes Sourced from Thermophilic Aspergillus Strains

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

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

Abstract: The industrial saccharification of starch into simple glucose syrups requires robust amylolytic enzymes that can resist thermal denaturation during high-temperature steam liquefaction loops. This study details the isolation, microstructural profiling, and kinetic optimization of high-yielding alpha-amylase complexes produced by a thermophilic fungal strain sourced from processing soil surrounding artisanal cassava processing mills. 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 fumigatus strain Cassava-A1. Response surface methodology optimized solid-state fermentation yields using wheat bran matrices. Maximum alpha-amylase activity (54.5 U/mL) was achieved at an incubation temperature of 50°C, an initial substrate pH of 6.0, 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 7.0 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 fumigatus; Solid-state fermentation; Thermal stability; Kinetic optimization; Starch saccharification

Manuscript Timeline: Received: November 10, 2015; Revised: December 18, 2015; Accepted: January 14, 2016; Published: June 03, 2016.

Citation: Nwosu, C. N., & Sato, H. M. (2016). Isolation, Structural Profiling, and Optimizing Kinetics of Amylolytic Complexes Sourced from Thermophilic Aspergillus Strains. International Journal of Chemistry, 7(6), 41–48.

International Journal of Chemistry | Vol. 7, No. 11, November 2016 | pp. 81–88

DOI: 10.46882/2016/IJC/000098

Article Type: Original Research Paper

Title: Electrochemical Properties and Charge Storage Profiles of Polypyrrole-Graphene Hydrogel Supercapacitor Electrodes

Names of Authors: U. B. Aliyu¹, K. Y. Lee²*

Authors’ Affiliations:
¹Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria.
²Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore.

Abstract: Fabricating highly efficient electrochemical energy storage units requires the development of hybrid polymer electrodes that exhibit high specific capacitance and fast ion diffusion kinetics. This research details the synthesis and electrochemical characterization of polypyrrole-graphene hydrogel (PPy-GH) self-assembling nanocomposites prepared via in situ chemical oxidative polymerization pathways. The surface topology and morphological features of the hybrid gels were analyzed using field emission scanning electron microscopy (FESEM), FT-IR, and Raman spectroscopy. FESEM imaging confirmed that a highly porous three-dimensional polypyrrole layer was uniformly deposited across the conductive graphene skeletal network. Electrochemical performance was investigated via cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) loops in a 1.0 M H₂SO₄ electrolyte system. The optimized PPy-GH hybrid electrode delivered a maximum specific capacitance of 485 F/g at a current density of 1.0 A/g, which was substantially higher than standalone pure polypyrrole films (215 F/g). Electrochemical impedance spectroscopy (EIS) data showed a very low charge-transfer resistance of 0.28 ohms, confirming accelerated ionic transport across the polymeric interface. Cyclic stability evaluations proved that the composite material retained 91.2% of its capacitive profile after 2000 continuous cycles.

Keywords: Polypyrrole; Graphene hydrogel; Energy storage; Supercapacitors; Cyclic voltammetry; Specific capacitance

Manuscript Timeline: Received: January 22, 2016; Revised: February 25, 2016; Accepted: March 18, 2016; Published: November 09, 2016.

Citation: Aliyu, U. B., & Lee, K. Y. (2016). Electrochemical Properties and Charge Storage Profiles of Polypyrrole-Graphene Hydrogel Supercapacitor Electrodes. International Journal of Chemistry, 7(11), 81–88.

International Journal of Chemistry | Vol. 7, No. 8, August 2016 | pp. 57–64

DOI: 10.46882/2016/IJC/000095

Article Type: Original Research Paper

Title: Spatial Variation, Speciation, and Carcinogenic Hazards of Chromium Formulations in Groundwater Networks Near Tanneries

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

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

Abstract: Industrial leather tanning operations discharge massive amounts of chromium-rich effluents into surrounding topsoils, causing heavy metal leaching into shallow drinking water wells. This study monitors the spatial variations, chemical speciation, and carcinogenic health risk profiles of chromium compounds across twenty household wells positioned around an active tannery industrial estate. Water monitoring was carried out over consecutive wet and dry cycles. Total chromium levels and carcinogenic hexavalent chromium [Cr(VI)] fractions were quantified utilizing ion chromatography coupled with inductively coupled plasma mass spectrometry (IC-ICP-MS). Total chromium concentrations ranged from 12.5 to 145.8 μg/L, with 45% of monitored groundwater sites surpassing the strict WHO drinkable contaminant threshold of 50.0 μg/L. Speciation analysis showed that toxic Cr(VI) was the dominant species, accounting for up to 68.4% of the total metal burden profiles at down-gradient coordinates. Seasonal mapping confirmed elevated chromium 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 2.4 in 10,000 near industrial boundaries, emphasizing an immediate public healthcare concern and a need for local membrane filtration arrays.

Keywords: Groundwater pollution; Chromium speciation; Hexavalent chromium; Ion chromatography; Tannery effluents; Cancer risk assessment

Manuscript Timeline: Received: December 02, 2015; Revised: January 14, 2016; Accepted: February 10, 2016; Published: August 03, 2016.

Citation: Awotunde, T. H., & Silva, R. A. (2016). Spatial Variation, Speciation, and Carcinogenic Hazards of Chromium Formulations in Groundwater Networks Near Tanneries. International Journal of Chemistry, 7(8), 57–64.

International Journal of Chemistry | Vol. 7, No. 1, January 2016 | pp. 1–8

DOI: 10.46882/2016/IJC/000088

Article Type: Original Research Paper

Title: Development and Validation of a Spectrophotometric Method for Quantitative Determination of Norfloxacin in Pharmaceutical Tablets

Names of Authors: E. O. Effiong¹, J. M. S. Cardoso²*

Authors’ Affiliations:
¹Department of Chemistry, University of Uyo, Uyo, Nigeria.
²Department of Pharmacy, University of Coimbra, Coimbra, Portugal.

Abstract: Developing rapid, low-cost analytical protocols is essential for routine quality monitoring and the detection of substandard antibiotic formulations in clinical testing laboratories. This paper describes the development and validation of a simple UV-Vis spectrophotometric method for the quantification of norfloxacin in tablet dosage forms. The analytical procedure relied on the reaction of norfloxacin with 2,4-dinitrophenylhydrazine in an acidic medium, generating a highly stable yellow-colored hydrazone derivative monitored spectrophotometrically at its absorption maximum of 420 nm. Method validation parameters followed the International Council for Harmonisation (ICH) guidelines. Excellent linearity was established over a concentration range of 2.0 to 25.0 mg/L with a correlation coefficient (R²) of 0.999. The limit of detection (LOD) and limit of quantification (LOQ) were determined to be 0.08 mg/L and 0.24 mg/L, respectively. Precision assessments yielded relative standard deviations (RSD) below 1.8%. The validated method was successfully applied to screen five commercial brands of norfloxacin tablets, producing recovery percentages between 98.6% and 101.4% with no interference from common tablet excipients, making it suitable for routine quality control setups.

Keywords: UV-Vis spectrophotometry; Norfloxacin; Chemical derivation; Method validation; Pharmaceuticals; Quality control

Manuscript Timeline: Received: May 02, 2015; Revised: June 15, 2015; Accepted: July 20, 2015; Published: January 03, 2016.

Citation: Effiong, E. O., & Cardoso, J. M. S. (2016). Development and Validation of a Spectrophotometric Method for Quantitative Determination of Norfloxacin in Pharmaceutical Tablets. International Journal of Chemistry, 7(1), 1–8.

International Journal of Chemistry | Vol. 6, No. 12, December 2015 | pp. 89–96

DOI: 10.46882/2015/IJC/000087

Article Type: Original Research Paper

Title: Green Corrosion Inhibition of Carbon Steel in Hydrochloric Acid Using Fruit Peel Extract of Citrus aurantifolia

Names of Authors: M. A. Haruna¹, S. Swaminathan²*

Authors’ Affiliations:
¹Department of Chemistry, Federal University of Technology, Minna, Nigeria.
²Department of Chemistry, Indian Institute of Technology, Madras, 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 methanolic fruit peel extract of Citrus aurantifolia (CA-Extract) on carbon steel in 1.0 M HCl 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 92.5% at a dose of 2.0 g/L. Polarization diagrams established that CA-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 = -21.4 kJ/mol), denoting a spontaneous physical adsorption mechanism driven by the presence of rich plant flavonoids.

Keywords: Carbon steel; Corrosion inhibition; Citrus aurantifolia; Electrochemical impedance spectroscopy; Polarization; Adsorption isotherm

Manuscript Timeline: Received: April 18, 2015; Revised: June 05, 2015; Accepted: July 12, 2015; Published: December 04, 2015.

Citation: Haruna, M. A., & Swaminathan, S. (2015). Green Corrosion Inhibition of Carbon Steel in Hydrochloric Acid Using Fruit Peel Extract of Citrus aurantifolia. International Journal of Chemistry, 6(12), 89–96.

International Journal of Chemistry | Vol. 6, No. 11, November 2015 | pp. 81–88

DOI: 10.46882/2015/IJC/000086

Article Type: Original Research Paper

Title: Geochemical Fractions, Spatial Distribution, and Bioavailability of Copper and Zinc in Coastal Lagoon Sediments

Names of Authors: C. I. Obi¹, S. H. Kim²*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, University of Port Harcourt, Port Harcourt, Nigeria.
²Department of Chemistry, Seoul National University, Seoul, South Korea.

Abstract: Total concentrations of heavy metals are insufficient to assess ecological risk in coastal bodies because environmental mobility and bioavailability depend heavily on specific chemical binding forms. This study evaluates the total concentration and geochemical speciation fractions of copper (Cu) and zinc (Zn) in surface sediments collected from an urban coastal lagoon exposed to municipal and industrial waste discharges. Quantitative analysis was performed using Atomic Absorption Spectrophotometry (AAS) following the modified BCR three-step sequential extraction procedure. The total metal concentrations followed the sequence: Zn > Cu across all sampling locations. Spatial mapping revealed significant pollutant accumulation near storm-water discharge channels. Speciation patterns demonstrated that a high proportion of zinc (42.5%) was associated with the acid-soluble and exchangeable fractions, suggesting high structural instability and bioavailable risks to benthic organisms. Conversely, copper was primarily bound within the organic and reducible matrices, indicating low immediate mobility under baseline pH conditions. The Risk Assessment Code (RAC) calculated for zinc indicated a high environmental hazard rating, highlighting a strong need for local effluent regulatory frameworks.

Keywords: Coastal lagoon; Sediments; Trace metals; BCR protocol; Geochemical speciation; Bioavailability

Manuscript Timeline: Received: April 02, 2015; Revised: May 22, 2015; Accepted: June 15, 2015; Published: November 02, 2015.

Citation: Obi, C. I., & Kim, S. H. (2015). Geochemical Fractions, Spatial Distribution, and Bioavailability of Copper and Zinc in Coastal Lagoon Sediments. International Journal of Chemistry, 6(11), 81–88.