International Journal of Chemistry

International Journal of Chemistry | Vol. 8, No. 7, July 2017 | pp. 49–56

DOI: 10.46882/2017/IJC/000106

Article Type: Original Research Paper

Title: Geochemical Speciation, Spatial Distribution, and Environmental Risk Assessments of Lead and Nickel in Estuarine Mudflats

Names of Authors: C. I. Obi¹, M. H. Chang²*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, University of Port Harcourt, Port Harcourt, Nigeria.
²Department of Marine Science, National Sun Yat-sen University, Kaohsiung, Taiwan.

Abstract: Monitoring total metal concentrations alone is inadequate to assess environmental risk in coastal estuarine zones because heavy metal mobility and bioavailability depend heavily on specific chemical binding forms. This study evaluates the total concentration and geochemical speciation fractions of lead (Pb) and nickel (Ni) in surface sediments collected from five mudflat nodes exposed to urban storm-water discharge channels. Quantitative analysis was performed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) following the five-step Tessier sequential extraction protocol. The total metal contents followed the sequence: Pb > Ni across all monitored coordinates. Spatial distribution evaluations revealed significant metal accumulation downriver from industrial zones. Speciation patterns demonstrated that a high proportion of lead (38.5%) and nickel (24.2%) existed within the exchangeable and carbonate-bound fractions, which are highly unstable and bioavailable to benthic organisms. Conversely, remaining fractions were bound within residual and organic-bound matrices, implying low immediate mobility under baseline pH conditions. The Risk Assessment Code (RAC) calculated for lead indicated a high environmental hazard threat level, highlighting a need for regulatory treatment protocols.

Keywords: Estuarine sediments; Speciation analysis; Tessier protocol; Bioavailability; Lead contamination; Risk Assessment Code

Manuscript Timeline: Received: August 05, 2016; Revised: September 18, 2016; Accepted: October 12, 2016; Published: July 08, 2017.

Citation: Obi, C. I., & Chang, M. H. (2017). Geochemical Speciation, Spatial Distribution, and Environmental Risk Assessments of Lead and Nickel in Estuarine Mudflats. International Journal of Chemistry, 8(7), 49–56.

International Journal of Chemistry | Vol. 8, No. 5, May 2017 | pp. 33–40

DOI: 10.46882/2017/IJC/000104

Article Type: Original Research Paper

Title: Transesterification Kinetics, Physicochemical Analysis, and Fuel Properties of Biodiesel Extracted from Madhuca indica Seeds

Names of Authors: M. C. Okonkwo¹, T. A. Prasetyo²*

Authors’ Affiliations:
¹Department of Industrial Chemistry, Enugu State University of Science and Technology, Enugu, Nigeria.
²Department of Chemical Engineering, Gadjah Mada University, Yogyakarta, Indonesia.

Abstract: Exploring alternative renewable fuel profiles derived from non-edible botanical seeds is crucial to sustain expanding transport grids while preserving food crop resources. This study focuses on the transesterification optimization and kinetic modeling of biodiesel production from crude Madhuca indica (Mahua) seed oil. Due to an elevated initial free fatty acid content (5.84 mg KOH/g), a two-step acid-base catalyzed transesterification route was deployed. The first step reduced the acid value below 1.0 mg KOH/g using 1.2% v/v sulfuric acid in methanol, followed by a base-catalyzed transesterification with potassium hydroxide (KOH). Fatty acid methyl ester (FAME) yield was optimized at 93.8% using a 6:1 methanol-to-oil molar ratio, a catalyst concentration of 1.0 wt% KOH, and a process temperature of 60°C for 90 minutes. Kinetic analysis established that the transesterification process followed pseudo-first-order kinetics with an activation energy of 41.5 kJ/mol. Fuel properties of the prepared biodiesel, including kinematic viscosity (4.32 mm²/s at 40°C), flash point (164°C), and cetane number (53), matched international ASTM D6751 regulatory specifications, showing its structural viability as a clean fuel feedstock.

Keywords: Madhuca indica; Biodiesel; Transesterification; Reaction kinetics; Activation energy; Fuel properties

Manuscript Timeline: Received: July 02, 2016; Revised: August 14, 2016; Accepted: September 10, 2016; Published: May 05, 2017.

Citation: Okonkwo, M. C., & Prasetyo, T. A. (2017). Transesterification Kinetics, Physicochemical Analysis, and Fuel Properties of Biodiesel Extracted from Madhuca indica Seeds. International Journal of Chemistry, 8(5), 33–40.

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. 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. 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.