African Journals Online
Bulletin of The Chemical Society of Ethiopia

Volume 17, Number 1, June 2003
ABSTRACTS

COMPARISON OF SOME PRECONCENTRATION METHODS FOR CERTAIN METAL IONS IN HUMAN MILK AND YOGURTS

F.O. Nwosu*, F.A. Adekola and E. Ibitoye

Department of Chemistry, University of Ilorin, P.M.B. 1515, Ilorin, Nigeria

ABSTRACT: Five samples each of yogurts and human milk were separately collected, deproteinized, pre-concentrated differently with 1% 8-hydroxyquinoline, 1% ammonium pyrrolidine-dithiocarbamate (APDC) and extracted with methyl-isobutylketone (MIBK). Activated carbon powder in HNO₃ was also used. The extracts obtained were analyzed using atomic absorption spectrometry for some metal ions. In yogurts, the powdered activated carbon in HNO3 exhibited the highest complexing ability with values of 0.04–0.17, 335–476, 1.52–3.82, 0.08–0.27, 0.09–0.28, 1.31–8.78 and 888–12693 mg/L concentration for Zn²⁺, Mg²⁺, Mn²⁺, Cr³⁺, Cu²⁺, Fe³⁺ and Ca²⁺, respectively. The concentrations of Zn²⁺, Mg²⁺, Mn²⁺, Cr³⁺, Cu²⁺, Fe³⁺ and Ca²⁺ ions were determined to be in the range of 0.02–0.03, 1.10–9.47, 0.05–0.11, 0.02–3.08, 0.01–0.87, 0.47–18.08, <0.01–278 mg/L, respectively, for APDC/MIBK extraction method. The complexing ability of APDC/MIBK appeared to be the lowest. The Co³⁺ and Cd²⁺ ions were only detected by activated carbon pre-concentration method. A more or less similar trend was obtained for human milk samples. For all samples, the complexing ability of each of the complexing agents varied from one metal ion to another.

STUDY OF ATMOSPHERIC POLLUTION LEVELS BY TRACE ELEMENTS ANALYSIS OF TREE BARK AND LEAVES

A.A. Olajire* and E.T. Ayodele

Department of Pure and Applied Chemistry, Ladoke Akintola University of Technology,

Ogbomoso, Nigeria

ABSTRACT: The concentrations of Pb, Cu, Zn, Ni, Fe, and Mn in leaf and bark samples of 7 tree species at 22 sampling locations with different pollution levels, in Ogbomoso, Nigeria, were investigated. The metal concentrations (mean ± RSD in mg g^-1) in leaf and bark samples, respectively, were: Pb, 203±70, 282±120; Cu, 19.5±4.2, 12.7±2.6; Zn, 42.7±12.9, 42.8±13.1; Ni, 30.0±11.1, 20.0±9.9; Fe, 869±348, 504±118; and Mn, 108±18, 73.7±13.8. The high-pollution automobile parking lots showed higher levels of these elements (p < 0.05). The correlation coefficient between element pairs of high and low-pollution automobile parking lots was carried out to determine the extent of relationship between the elements investigated.

BIODIESEL FUELS FROM PALM OIL, PALM OIL METHYLESTER AND ESTER-DIESEL BLENDS

V.I.E. Ajiwe¹*, V.O. Ajibola² and C.M.A.O. Martins²

¹Department of Science Technology, Nnamdi Azikiwe University, P.M.B. 5025, Awka, Nigeria

²Department of Chemistry, Ahmadu Bello University, Nigeria

ABSTRACT: Because of increasing cost and environmental pollution effects of fossil fuels, palm oil, its methylester and ester-diesel blends were analyzed comparatively with diesel for their fuel properties that will make them serve as alternatives to diesel in diesel engines. Equally, the samples were comparatively analyzed for their trace metal composition in relation to corrosion. Also the bond structure/stability of the samples in relation to diesel were monitored with a Fourier transform infrared spectrometer. Results confirmed that most methylester blends with diesel fell within the grade 2D while the oil, methylester and 90:10 blend fell into 4D grade diesel fuels. From bond structure/stability comparison, all the samples were stable at 28 ºC and had similarity in structure with diesel. All samples are commercializable. The trace metal composition of most samples was below that of the diesel with exception of Mn, Pb and Zn. The total acid numbers of all samples were below that of diesel and would not cause corrosion. It is recommended that processing of these samples should be done to conserve fossil fuel and as alternative diesel fuels in diesel engines.

SPECTROSCOPIC STUDIES OF SOME LANTHANIDE(III) NITRATE COMPLEXES SYNTHESIZED FROM A NEW LIGAND 2,6-BIS-(SALICYLALDEHYDE HYDRAZONE)-4-CHLOROPHENOL

M. Gaye*, F.B. Tamboura, A.S. Sall

Université Cheikh Anta Diop, Faculté des Sciences et Techniques, Département de Chimie, Dakar, Sénégal

ABSTRACT: The ligand 2,6-bis-(salicylaldehydehydrazone)-4-chlorophenol (H₅L) and its binuclear lanthanide(III) nitrate complexes {[Ln₂(H₄L) ₃(NO₃)](NO₃) ₂.mH₂O} where Ln = La, Ce, Pr, Nd, Sm, Gd, Dy, Er, Yb and Y, have been synthesized. The complexes were characterized by chemical analysis, conductance, magnetic moment measurements and infrared spectra. Infrared study indicates that the ligand behaves both as neutral and ionic O donors and as neutral N donors.

STUDIES ON TRANSITION METAL COMPLEXES OF HERBICIDAL COMPOUNDS. II: TRANSITION METAL COMPLEXES OF DERIVATIZED 2-CHLORO-4-ETHYLAMINO-6-ISOPROPYLAMINO-S-TRIAZINE (ATRAZINE)

Worku Dinku¹, Negussie Megersa¹, V.J.T. Raju^1,2, Theodros Solomon¹, Jan Åke Jönsson³ and Negussie Retta¹*

¹Department of Chemistry, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia

²Department of Chemistry, Osmania University, Hyderabad 500 007, India

³Department of Analytical Chemistry, Lund University, Box 124, S-221 00 Lund, Sweden

ABSTRACT: 2(2-Hydroxyethyl)hydrazino-4-ethylamino-6-isopropylamino-s-triazine (HEATZ), a derivative of 2-chloro-4-ethylamino-6-isopropylamino-s-triazine, atrazine (ATZ) – a well known herbicide has been studied for complex formation with cobalt(II), nickel(II), and copper(II). Analytical, conductance, thermal, and spectral studies suggest that HEATZ is a monobasic NNO donor and it forms binuclear octahedral metal complexes, possessing alkoxide bridging. Cobalt(II) complex exhibits thermochromism. Antimicrobial studies on E. coli and S. aureus show the absence of growth inhibitory activities for HEATZ and its metal complexes which is attributed to the combined effect of derivatization of ATZ and metal complexation.

POTENTIOMETRIC STUDY OF COMPLEXES FORMED BETWEEN

(S)-α-AMINO-3-HYDROXY-5-METHYL-4-ISOXAZOLEPROPANOIC ACID AND SOME TRANSITION METAL IONS

Onindo Charles Otieno*

Chemistry Department, Kenyatta University, P.O. Box 43844, Nairobi 00100, Kenya

ABSTRACT: Potentiometric study has been carried out on (S)-α-amino-3-hydroxy-5-methyl-4-isoxazolepropanoic acid [AMPA] in the presence of transition metal ions to measure the thermodynamic stabilities of its complexes; and hence give an insight into its possible role in binding metal ions. The nitrogen donor atom of AMPA is alanine-like with the addition of a hydroxy-isoxazole ring. The first complex [CuHL], which is fully formed by pH 4 is proposed to be with {N,O} bonding which results in the formation of a stable five membered chelate ring. The [CuL] species has some enhanced stability which suggest some form of tridentate co-ordination through {H₂N, COO-, O-}. When this changes to [CuL₂], one of these bonds must be broken if Cu(II) is to have a maximum co-ordination number of four. Zn and Cd formed very similar comlexes with AMPA, these were [ZnHL], [ZnL], [ZnL₂] and [CdHL], [CdL], [CdL₂], respectively. [ZnL] and [ZnL₂] are significantly more stable than alanine, suggesting tri-dentate co-ordination. [CdHL] complex is again very important suggesting some bidentate chelation.

SYNTHESIS AND FUNGICIDAL ACTIVITY OF ACETYL SUBSTITUTED BENZYL DISULFIDES

E.T. Ayodele*, A.A. Olajire, O.S. Amuda and S.O. Oladoye

Department of Pure and Applied Chemistry, Ladoke Akintola University of Technology, Ogbomoso, Nigeria

ABSTRACT: The synthesis and fungicidal activity of acetyl substituted benzyl disulfides 1(a – g) are reported. The compounds were characterized by elemental analysis, nuclear magnetic resonance (¹H NMR and ¹³C NMR) and mass spectrometric techniques. The results of the biological screening showed that the synthesized compound possess very high fungicidal activity.

A NOVEL GLYCOSIDIC STEROIDAL ALKALOID FROM SOLANUM  ACULEASTRUM

Alphonse W. Wanyonyi, Paul K. Tarus, Sumesh C. Chhabra*

Chemistry Department, School of Pure and Applied Sciences, Kenyatta University,

P.O. Box 43844, Nairobi, Kenya

ABSTRACT: The root bark of Solanum aculeastrum Dunal yielded a new steroidal alkaloid glycoside characterised as (25R)-3β-{O-α-L-rhamnopyranosyl-(1→2)-[O-β-D-glucopyranosyl-(1→4)-O-α-L-rhamnopyranosyl-(1→4)]-β-D-glucopyranosyl}-22α-N-spirosol-5-ene. The structure was established by spectroscopic analysis and comparison with published data of similar compounds reported in literature.

INTRA-SPECIES VARIATION OF THE PROPERTIES OF GUM EXUDATES FROM ACACIA SENEGAL VAR. SENEGAL AND ACACIA SEYAL VAR. FISTULA FROM TANZANIA

Gaspar S. Mhinzi

Chemistry Department, University of Dar es Salaam, P.O. Box 35061, Dar es Salaam, Tanzania

ABSTRACT. Gum exudates from Acacia senegal var. senegal and Acacia seyal var. fistula from Tanzania have been analyzed and their inter- and intra-species variation of their properties evaluated. The results show that significant inter-species variation of the properties of the gum exudates from the two species exist, whereas only some parameters show significant intra-species variation. The specific optical rotations of the gum exudates have been found to vary from –43.2º to –52º for Acacia senegal var. senegal and +36.0º to +60.0º for A. seyal var. fistula. Likewise, the acid equivalent weights (AEWs) have been found to vary from 1093 to 1920 for A. senegal var. senegal and 1063 to 1749 for A. seyal var. fistula. Significant intra-species variation for the tannin content has also been observed for the species studied, whereas the nitrogen content has been observed to vary significantly only in A. seyal var. fistula. The results in this study show that the variation of the properties among batches of commercial Acacia gum may be due to admixture of gums from different Acacia species as well as intra-species variation.

THEORETICAL STUDY OF THE CATALYTIC DESULFURIZATION MECHANISM OF THIIREN AND ITS METHYL DERIVATIVE

J.B. Mensah¹*, Y.G. S. Atohoun¹, L.O. Olatunji²

¹Laboratoire de Chimie Théorique, FAST/Université d’Abomey-Calavi, 03 BP 3409 Cotonou, Bénin

²Laboratoire de Physique Théorique, Université d’Abomey-Calavi 08 BP 451 Cotonou, Bénin

ABSTRACT: The desulfurization process of compounds implicates two steps. The first step is the adsorption process on the catalytic site and the second, the breaking of the carbon-heteroatom bond leading to the heteroatom elimination. The adsorption process of thiiren have been studied and published in previous works. The results obtained on MoS₃H₃₊ and MoS₄H₄ have shown that the adsorption of this molecule was very good on the two and three anionic vacancies sites based on molybdenum. In the present study, we have carried out the adsorption according to vertical and horizontal geometries of dihydrothiiren, methylthiiren, and methyldihydrothiiren, and the desulfurization of all these molecules including thiiren molecule. The results obtained have shown that, the desulfurization of thiiren and its methyl derivate pass through the hydrogenation of the aromatic ring on the two types of catalytic sites.

SPECIATION OF CADMIUM MIXED LIGAND COMPLEXES

IN SALT WATER LAKES

John L. Kituyi¹*, Henry M. Thairu², Justin Irina³ and Knut H. Schroder⁴

¹Moi University, Department of Chemistry, Box 1125, Eldoret, Kenya

²Jomo Kenyatta University of Agriculture and Technology, Box 62000, Nairobi, Kenya

³Commission for Higher Education, Box 48823, Nairobi, Kenya

⁴University of Trondheim, Department of Chemistry, N-7055 Trondheim, Norway

ABSTRACT: Amalgam voltammetry has been used to study heavy metal interaction in model lake water in KNO₃ at 23 ºC at concentration levels of genuine lake water. The hanging drop amalgam electrode was prepared in situ before exchanging the medium for the sample solution. Half-wave potentials at two metal ion concentrations were measured, one at the actual concentration in the lake while the other at a much lower one. The experimentally determined shifts in half-wave potentials are used to compute several formation constants.

At the natural [CO₃^2-] of 0.5 M in the lake, the main contributor to the speciation of cadmium is [Cd(CO₃Cl₂)]^2-. At high [Cd²⁺], the DPASV detects the presence of free Cd²⁺ ions, hence, potential polluting effect, while the amalgam reports [Cd(CO₃)₂Cl)]^3- to be dominant above [CO₃^2-] = 0.8 M. There is a variation in the number of complexes detected, their stabilities and percentage distribution in the two methods. Cd²⁺ ion concentration also affects the number of complexes formed and their stabilities.

ELECTROCHEMICAL OXIDATION OF NICLOSAMIDE AT A GLASSY CARBON ELECTRODE AND ITS DETERMINATION BY VOLTAMMETRY

Hailemichael Alemu*, Ntai M. Khoabane and Potlaki F. Tseki

Department of Chemistry, National University of Lesotho, P.O. Roma 180, Roma, Lesotho, Southern Africa

ABSTRACT: Cyclic voltammetry, square-wave voltammetry and controlled potential electrolysis have been used to study the electrochemical oxidation behaviour of niclosamide at a glassy carbon electrode. The number of electrons transferred, the wave characteristics, the diffusion coefficient and reversibility of the reactions have been investigated. Following optimisation of voltammetric parameters, pH, and reproducibility, a linear calibration curve over the range 1 x 10^-6 – 1 x 10^-4 mol dm^-3 niclosamide was achieved. The detection limit was found to be 8 x 10^-7 mol dm^-3. For eight successive determinations of 1 x 10^-5 mol dm^-3 niclosamide, a relative standard deviation of 3.6% was obtained. This voltammetric method was applied for the determination of niclosamide in tablets.

SHORT COMMUNICATIO

COMPARATIVE STUDY OF TRACE ELEMENT LEVELS IN SOME LOCAL VEGETABLE VARIETIES AND IRRIGATION WATERS FROM DIFFERENT LOCATIONS IN ILORIN, NIGERIA

O.O. Dosumu*, N. Salami and F.A. Adekola

Department of Chemistry, University of Ilorin, P.M.B. 1515, Ilorin, Nigeria

ABSTRACT: The level of heavy metals in two varieties of vegetables harvested during the dry and wet seasons from seven different locations in Ilorin, Nigeria, were determined. The correlation between the level of metals in the vegetables and the irrigation water was also studied. Vegetables harvested during the dry season were found to contain higher level of toxic metals. Low water quality, accumulation of particulate after rainless period and nearness of some vegetable gardens to major and well travelled roads appeared to be the major contributory factors. Amaranthus hybridus seemed to have higher metal accumulation capacity compared to Corchorus olitorius mannii.

A NEW ISOFLAVONE FROM STEM BARK OF MILLETTIA DURA

Solomon Derese1, Abiy Yenesew¹*, Jacob O. Midiwo¹, Matthias Heydenreich² and

Martin G. Peter²

¹Department of Chemistry, University of Nairobi, P.O. Box 30197, Nairobi, Kenya

²Institut für Chemie, Universität Potsdam, P.O. Box 60 15 53, D-14415 Potsdam, Germany

ABSTRACT: A new isoflavone (7,3’-dimethoxy-4’,5’-methylenedioxyisoflavone) and three known isoflavones [isoerythrinin A 4’-(3-methylbut-2-enyl) ether, isojamaicin and nordurlettone] were isolated from the stem bark of Millettia dura (Leguminosae). The structures were determined by spectroscopic methods.