Open Access Original Research Article

Simultaneous Determination of Pb(II), Cu(II) and Ni(II) with MEDTA by Ultraviolet and Visible Derivative Spectrophotometry

M. C. Fernández-Feal, J. M. Castro-Romero, J. M. Fernández-Solís

Chemical Science International Journal, Page 1-8
DOI: 10.9734/CSJI/2018/40983

Aims: Since the end of the nineteenth century, when Werner proposed his theory of co-ordination, the study of metallic compounds has continued to attract the interest of researchers. The present work had as its aim to achieve simultaneous determination of Pb(II), Cu(II) and Ni(II) by means of UV-VIS and derivative spectrophotometry, using methyl-ethylene-diamine-tetraacetic acid, MEDTA, as a chelating agent.

Study Design: The visible and ultraviolet spectroscopy allows both to identify a chemical substance (qualitative analysis) and to determine its concentration (quantitative analysis). In the work, the UV-VIS and derivative spectrophotometry is used for the determination simultaneous of Pb(II), Cu (II) and Ni (II). The method proposed uses methyl-ethylene-diamine-tetracetic acid (MEDTA) as a chelating agent and absorption spectrophotometry for quantification.

Place and Duration of Study: The study is part of a doctoral thesis, was conducted in the Analytical Chemistry Department of the University of A Coruña.

Methodology and Results: In the range of wavelengths between 200 nm and 500 nm, the complexes formed by MEDTA with Pb(II) or Cu(II) present a single absorption peak at 256 nm and 272 nm respectively, whilst the complex formed with Ni(II) presents two peaks at 250 nm and 380 nm. In the samples in which the three elements are present, the spectrum shows two peaks: the first at 260 nm, due to the superposition of the individual absorption peaks of the cations at 250, 256 and 272 nm and the second at 380 nm, characteristic of Ni (II). It is necessary the joint use of the normal or direct spectrum (zero order) and the first derivative thereof by means of the zero-crossing-point method for its simultaneous determination.

In the development of this method the influences exercised by pH, time and temperature were determined. The reproducibility of the method proposed was checked, as was the interference from certain of the more frequent anions and cations that might affect the determination.

Conclusion: As long as the optimum conditions indicated are maintained, the method of analysis proposed makes possible the simultaneous determination of Pb(II), Cu(II) and Ni(II) using MEDTA as a chelating agent and UV-VIS and derived spectrophotometry. Then method was successfully tested through the use of blind samples.

Open Access Original Research Article

Synthesis and Encapsulation of bis-eugenol in a Mesoporous Solid Material: Enhancement of the Antioxidant Activity of a Natural Compound from Clove Oil

Vanina A. Guntero, Cristián A. Ferretti, Pedro M. Mancini, María N. Kneeteman

Chemical Science International Journal, Page 1-10
DOI: 10.9734/CSJI/2018/41105

In the present work, microwave extraction conditions to recover high eugenol content in the crude extract from clove were investigated. The effect of factors like temperature, stirring, time, liquid: Solid ratio and solutions of solvent were evaluated with Taguchi’s method. The eugenol content was determined by gas chromatography. From the isolated eugenol, the bis-phenol was synthesized by the dimerization of eugenol. The encapsulation of bis-eugenol on the mesoporous silica was carried out by a microwave assisted process. Previously, mesoporous silica SBA-15 was prepared by hydrothermal synthesis using Pluronic P123 triblock copolymer as a surfactant. The bis-eugenol encapsulated in SBA-15 was characterized by physicochemical techniques. The results indicated that the encapsulation of bis-eugenol in the pores of silica occurred through weak interactions of an electrostatic nature without producing chemical changes in the antioxidant property. The antioxidative activity of eugenol, bis-eugenol and bis-eugenol/SBA-15 system was examined by phosphomolybdenum assay. Among these materials, a remarkably high antioxidant activity was found in bis-eugenol encapsulated in SBA-15. These resultas suggest the possibility of applying this system as an antioxidant active packaging in the future.

Open Access Original Research Article

Chemical Reactivity Theory Applied to the Calculation of the Local Reactivity Descriptors of a Colored Maillard Reaction Product

Juan Frau, Daniel Glossman-Mitnik

Chemical Science International Journal, Page 1-14
DOI: 10.9734/CSJI/2018/41452

This computational study assessed ten density functionals that include CAM-B3LYP, LC-ωPBE, M11, M11L, MN12L, MN12SX, N12, N12SX, ωB97X, and ωB97XD related to the Def2TZVP basis set together with the SMD solvation model. These are assessed in calculating the molecular properties and structure of the pyrrolopyrrole-2-carbaldehyde molecule (PPA) in water. The chemical reactivity descriptors for the systems are calculated via the Conceptual Density Functional Theory. The choice of active sites applicable to nucleophilic, electrophilic as well as radical attacks is made by linking them with Fukui functions indices, electrophilic Parr functions, and condensed dual descriptor Δf(r).

The predicted Maximum absorption wavelength tends to be considerably accurate relative to the experimental value. The study found the MN12SX and N12SX density functionals to be the most appropriate in predicting the chemical reactivity of this molecule.

Open Access Original Research Article

Isotherm and Kinetic Studies on the Adsorptive Removal of Metanil Yellow and Neutral Red Dyes Using Copper Oxide Nanoparticles

Muhammad Adamu Ibrahim, Muhammad Bashir Ibrahim

Chemical Science International Journal, Page 1-10
DOI: 10.9734/CSJI/2018/41169

This study investigated the adsorption property of copper oxide nanoparticles (CuO-NPs) for the removal of Metanil Yellow (MY) and Neutral Red (NR). The influence of variables such as contact time, initial concentration and pH for the adsorption process were investigated. The percentage removal and optimum contact time for the removal of MY and NR were obtained as 70.7% during 25 min and 56.9% over 30 min respectively. The experimental isotherms data were analyzed using Langmuir, Temkin, Freundlich and Dubinin-Radushkevich (D-R) isotherms and it was observed that MY fits closely to Temkin isotherm with an R2 value of 0.860 and NR fits more to D-R isotherm with R2 0.953. The kinetics of both MY and NR dyes fits better to pseudo-second order with the experimental values of qe 2.844 and 3.536 for NR and MY respectively been closer to the calculated values of the qe 2.739 and 3.222 for NR and MY respectively. Effect of pH of both dyes shows that they adsorb better at the initial pH of 3.37 and 5.09 for NR and MY respectively. Lower values of mean square energies of 0.354 for NR and 0.791 kJ/mol for MY indicates that the adsorption process is physical. The results indicated that copper oxide nanoparticle can be used as a low-cost adsorbent for the removal of MY and NR from aqueous solutions.

Open Access Review Article

Theoretical Study of the Chemical Reactivity of Five Schiff Bases Derived From Dapsone by the DFT Method

Jean Stéphane N’dri, Mamadou Guy-Richard Koné, Charles Guillaume Kodjo, Ahmont Landry Claude kablan, Sopi Thomas Affi, Lamoussa Ouattara, Nahossé Ziao

Chemical Science International Journal, Page 1-11
DOI: 10.9734/CSJI/2018/41427

This theoretical study of chemical reactivity was conducted using the method of the Density Functional Theory (DFT), with B3LYP/6-311G (d, p) as calculation level. A series of five (05) Schiff bases derived from 4.4 '-diaminodiphenylsulfone (Dapsone) was concerned and allowed to predict the chemical reactivity of these compounds. Molecular geometries and electronic properties such as the energies of the frontier molecular orbitals (HOMO and LUMO), ionization potential (I), and electron affinity (A) were examined to obtain a better overview of the molecular properties. Thus compound 4, whose energy gap between the frontier orbitals (HOMO and LUMO) is ΔEgap = 3.910 eV appears to be the most polarizable. It is the most reactive with the lowest kinetic stability compared to all the studied molecules. The values of the global reactivity descriptors confirmed the great chemical reactivity of the compound 4. Local indices of reactivity and dual descriptors were calculated to indicate the probable sites of Electrophilic and nucleophilic attacks of the various studied compounds.