Scielo RSS <![CDATA[South African Journal of Chemistry]]> http://www.scielo.org.za/rss.php?pid=0379-435020180001&lang=pt vol. 71 num. lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Synthesis, Characterization and Biocompatibility of a Multifunctional Gold Nanoparticle System for the Delivery of Single-Stranded RNA to Lymphocytes</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100001&lng=pt&nrm=iso&tlng=pt The use of RNA macromolecules as therapeutic agents for HIV and other infectious diseases is promising but limited by suboptimal delivery to the target site. With HIV infection, this is particularly challenging since lymphocytes are particularly difficult to transfect. This paper describes an innovative strategy for the intracellular delivery of a novel single-stranded RNA (oligoribonucleotide) with putative anti-HIV activity. This strategy is based on a PEGylated gold nanoparticle scaffold covalently linked to the thiol-modified oligoribonucleotide via a cleavable N-succinimidyl 3-(2-pyridyldithio) propionate (SPDP) linker molecule. The nanoparticle was then coated with a cationic polymer (polyethyleneimine) to facilitate cell entry and endosomal escape. A synthetic anti-CD4 cyclic targeting peptide was attached to the polyethyleneimine-coated nanoparticle via an SPDP linker molecule, in an attempt to enhance uptake and selectivity. Synthesis, characterization, SPDP and RNA loading, cytotoxicity and antiviral activity of the nanoparticle are described. Approximately 45 000 strands of RNA were taken up per lymphocyte. Uptake was limited by relatively inefficient loading of RNA onto the gold nanoparticle surface (1 strand per 4.8 nm² of nanoparticle surface area) and significant aggregation of the nanoparticle in physiological solutions. No antiviral activity was demonstrated, possibly due to insufficient intracytoplasmic delivery of the RNA. <![CDATA[<b>Performance of Mn<sup>2+</sup> modified Bentonite Clay for the Removal of Fluoride from Aqueous Solution</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100002&lng=pt&nrm=iso&tlng=pt A low-cost adsorbent produced from Mn2+-modified bentonite clay was evaluated for groundwater defluoridation. Batch experiments were used to evaluate the effect of contact time at various adsorbent dosages, adsorption isotherms and the effect of pH on fluoride removal. The results showed that the optimum F- uptake occurred within the first 30 min contact time and the percentage removal increased with increasing adsorbent dosage. The data fitted better to pseudo-second-order reaction indicating that Fadsorption occurred via chemisorption. The Weber-Morris model of intra-particle diffusion revealed that both surface and intra-particle diffusion processes were involved during the F- adsorption process. Furthermore, the batch results showed that pH of the solution governed the percentage of fluoride removal with the optimum of 75.2 % fluoride removal achieved at pH 4. The adsorbent chemical stability assessment showed that chemical species were leached at trace concentrations which are within the South African National Standards (SANS) limits. Electrostatic attraction and ion-exchange were established as the major mechanisms responsible for fluoride adsorption at acidic pH and at moderate to alkaline pH levels, respectively. The study demonstrated that Mn2+ intercalated bentonite clay has potential for application in defluoridation of groundwater. <![CDATA[<b>A Validated Method for the Detection and Quantitation of Synthetic Cannabinoids in Whole Blood and Urine, and its Application to Postmortem Cases in Johannesburg, South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100003&lng=pt&nrm=iso&tlng=pt A LC-HRMS (liquid chromatography coupled with high resolution mass spectrometry) method for the detection and quantitation of several synthetic cannabinoids (JWH-018, JWH-019, JWH-073, JWH-081, JWH-122 JWH-200, JWH-250, AM-2201, (±)-CP 47,497, (C8)-CP 47,497, HU-211) and selected metabolites (JWH-018 N-(4-hydroxypentyl) and JWH-073 N-(3-hydroxybutyl)) in whole blood and urine was developed and validated. These methods were applied to postmortem cases from the Johannesburg Forensic Pathology Services Medicolegal Laboratory (FPS-MLL) to assess the prevalence of these synthetic cannabinoids amongst the local postmortem population. Urine samples were extracted utilizing a solid phase extraction (SPE) method, while blood samples were extracted utilizing liquid-liquid extraction (LLE) method. The accuracy of the analytes ranged from 88-107 % in whole blood (relative standard deviation (RSD) = 7.5-15.0 %), and from 95-109 % in urine (RSD = 4.9-11.9 %). The limits of detection (LOD) and the limits of quantitation (LOQ) for the analytes ranged between 0.675 ng mL-1 and 3.375 ng mL-1 in whole blood, and between 0.225 ng mL-1 to 3.375 ng mL-1 in urine. None of the postmortem cases tested positive for any of the targeted analytes. The sample population could be extended to living subjects such as those in drug rehabilitation centres or in hospitals to obtain a more accurate representation of the overall usage in South Africa. <![CDATA[<b>Anti-corrosion Properties of Areca Palm Leaf Extract on Aluminium in 0.5 M HCl Environment</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100004&lng=pt&nrm=iso&tlng=pt The aluminium corrosion inhibition behaviour in the presence of Areca palm leaves (AL) extract in hydrochloric acid (0.5 M) medium was examined by chemical (mass loss), AC impedance spectroscopy, potentiodynamic polarization and surface (scanning electron microscopy) methods. Aluminium protection rates increased with an increase in the amount of AL extract to the 0.5 M HCl system and decreased with increasing in the contact time of aluminium metal and temperature of 0.5 M HCl solution. Arrhenius equation was applied in the determination of activation energy values. The other activation parameters such as activation entropy and enthalpy values were obtained from the transition state plot. The adsorption of AL extract species on the Al surface in 0.5 M HCl solution follows the Langmuir adsorption mechanism. Tafel curves reflect the mixed (both anodic and cath-odic) inhibition behaviour of green inhibitor (AL extract species) on electrode surface (Al) in 0.5 M system. Impedance method indicates that the Al dissolution in hydrochloric acid environment was fully hindered by charge transfer process. The Al surface morphology was examined by applying scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. <![CDATA[<b>Flow Injection Spectrophotometric Determination of Glyphosate Herbicide in Wheat Grains <i>via </i>Condensation Reaction with p-Dimethylaminobenzaldehyde</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100005&lng=pt&nrm=iso&tlng=pt A fast and sensitive method was developed for determination of glyphosate, using flow injection analysis. The analyte was converted to a photoactive product that shows maximum absorbance at 405 nm. Beer's law was obeyed over a range of 0.7-20μg mL-1. The limit of detection and quantification were found to be 0.20 ± 0.01 and 0.70 ± 0.02 μg mL-1 with a high sample throughput of 60 samples h-1. The investigation of interference effect shows that among the compounds studied, only aminomethyl phosphonic acid exhibits a signal enhancing effect when present in higher concentration ratio with the analyte and this can be assumed to be a limitation of the present method. The percentage recoveries and residue of glyphosate in wheat grains samples, were found in the range of 90.0 ± 0.6 % to 93.0 ± 0.6 % and 1.13 ± 0.009 μg g-1, respectively. <![CDATA[<b>Hydrazide Derivatives: An Overview of Their Inhibition Activity against Acid Corrosion of Mild Steel</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100006&lng=pt&nrm=iso&tlng=pt This paper gives an overview of the application of hydrazide derivatives in acid media as corrosion inhibitors of mild steel. In chemical and petrochemical industries, mild steel is the major constructional material widely used. Acid solutions have been commonly used in these industries as pickling agents to remove rust or any scale from the mild steel surface. The excessive dissolution of mild steel in such aggressive medium can be best controlled by addition of suitable organic inhibitors. Hydrazide derivatives are widely used in such applications as mild steel corrosion inhibitors. The various factors which influence the corrosion inhibition efficiency of different hydrazide derivatives have been discussed. The information provided is useful for various industries where corrosion inhibitors are needed to protect mild steel structures which are being exposed to hydrochloric or sulphuric acid solutions. <![CDATA[<b>Optimization and Electrochemical Study on the Control of Mild Steel Corrosion in Hydrochloric Acid Solution with Bitter Kola Leaf Extract as Inhibitor</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100007&lng=pt&nrm=iso&tlng=pt Response surface methodology was applied to predict the optimum control of mild steel corrosion in acid medium with bitter kola leaf extract as inhibitor. The experiment was carried out to investigate the mutual interactions between the considered independent variables and the expected responses. Thermometric, gravimetric, potentiodynamics polarization and electrochemical impedance spectroscopy were used in the corrosion inhibition study. As a supplementary technique, infrared spectroscopy was used to analyze the pure extract and corrosion products and it was observed that some peaks shifted while some disappeared. Inhibition efficiencies of 88.24 %, 86.81 %, 90 %, 89.5 % and 85.3 % were obtained from optimization, thermometric, gravimetric, potentiodynamics polarization and electrochemical impedance spectroscopic techniques, respectively. The bitter kola leaf extract behaved as a mixed-mode inhibitor. Application of response surface methodology in this study was found to be good in predicting the optimum range for controlling of metal corrosion thereby reducing the number of experimental runs. <![CDATA[<b>The Role of Bronsted and Lewis Acidity in the Green Synthesis of Homopropargyl Alcohols over HZSM-5</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100008&lng=pt&nrm=iso&tlng=pt A highly efficient and simple reaction under exceptionally mild conditions is shown for the synthesis of biologically and pharma-ceutically active molecules of homopropargyl alcohol using HZSM-5 as the catalyst. Products analyzed by IR, 1H NMR, 13C NMR and GC-MS showed consistent yields of 98 % of the alcohol, even with respective recycles of the regenerated catalyst. The reaction was also carried out with selected mineral acids, acidic oxides and other acidic catalysts to compare reactivity and the influence of the type of acidity involved in the reaction. The results indicate that the presence of both Bronsted and Lewis acidity is beneficial for inducing a high rate of reaction when compared to systems having either predominantly Bronsted or Lewis acidity. <![CDATA[<b>The effect of synthesis method on the structure, and magnetic and photocatalytic properties of hematite (</b><em><strong>α</strong></em><strong>-</strong><b>Fe<sub>2</sub>O<sub>3</sub>) nanoparticles</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100009&lng=pt&nrm=iso&tlng=pt Samples of hematite (a-Fe2O3) nanoparticles have been synthesized through the co-precipitation route in cetyltrimethyl-ammonium bromide (Hem_PR), via a citric acid sol-gel method (Hem_SG) and a modified sol-gel method in Tween 20 (Hem_TW), and each were annealed at three different temperatures (400,500 and 600 °C). The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission and high-resolution electron microscopy (TEM and HRTEM), Mössbauer spectroscopy and by means of a vibrating sample magnetometer (VSM). In addition, the photocatalytic behaviour of each sample was tested on the degradation of rhodamine B (RhB) in solution. All the characterization techniques showed the formation of phases of pure hematite nanoparticles with improved crystallinity after higher temperature annealing. However, the nanoparticles synthesized in Tween 20 showed the smallest particle size and highest BET surface area, saturation magnetization and photocatalytic activity. Of particular note was the ability of Tween 20 to control the growth of the particles so that grain sizes well below 10 nm were obtained. Thus, Tween 20, when used as a surfactant in the sol-gel route, can serve to improve the physical properties of synthesized hematite nanoparticles. <![CDATA[<b>Simultaneous determination of nitrate, nitrite and phosphate in environmental samples by high performance liquid chromatography with UV detection</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100010&lng=pt&nrm=iso&tlng=pt An HPLC method using an UV detector was developed for the simultaneous determination of nitrites, nitrates and phosphates in environmental samples. Chromatographic separation was achieved isocratically on a Phenomenex Synergi Polar-RP LC column using acetonitrile and acidified water (pH 2.7) at 60:40 v/v as mobile phase. Baseline resolution of all the three analytes was achieved within 3 min. The developed method was applied to water samples obtained from the wastewater treatment plant in Gaborone, Botswana. The use of HPLC technique in this study demonstrated its ability to carry out a simultaneous determination of NO2",NO3" and PO4(3-) in water samples. The treatment plant was found to be functioning within expectations, removing 97.6 % NO2-, 88.0 % NO3- and 90.9 % PO4(3-) from the received wastewater. Results of the developed method were comparable with those of the traditional ion chromatography method, showing accuracy values between 95.22 % and 98.04 %. The precision of the method for the determination of all analytes was determined by RSD values, all of which were lower than 5 %. The method is of low cost, fast, has an easy procedure and avoids the use of many reagents - some of which may be hazardous. <![CDATA[<b>Determination of Dichlorodiphenyltrichloroethane (DDT) and metabolites residues in fish species from eastern Lake Tanganyika</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100011&lng=pt&nrm=iso&tlng=pt In this study, the levels and status of dichlorodiphenyltrichloroethane (DDT) residues in fish samples collected from Eastern Lake Tanganyika were investigated. The analytes were determined using gas chromatography equipped with an electron capture detector (GC-ECD) and by gas chromatography-mass spectrometry (GC-MS). The compounds p,p'-DDE (4,4'-DDE), p,p'-DDD (4,4'-DDD), o,p'-DDT (2,4'-DDT) and p,p'-DDT (4,4'-DDT) were detected in all the samples, with total DDT concentrations ranging from 23 ± 8.3 to 339 ± 27 kg-1 fresh weight and 1736 ± 1388 kg-1 to 25 552 ± 4241 kg-1 lipid weight. The highest concentrations of total DDT were detected in Lates stappersii species. The ratios of the metabolites (DDD + DDE) to the parent compound (p,p'-DDT) were low (< 1) in all the fish samples, indicating exposure to fresh DDT. The concentrations of the DDT residues exceeded the extraneous maximum residue limit of 1.0 /ug kg-1, indicating risks and concerns for public health and the environment because of the indication of fresh application of banned pesticides and bioaccumulation. There is need for continued monitoring of the residues in Lake Tanganyika environs and controlling the pesticides used in the area. <![CDATA[<b>Fabrication of nitrogen donor macro- and meso-porous materials for group 11 metal ions sorption</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100012&lng=pt&nrm=iso&tlng=pt Macro(meso) porous polymer materials were prepared via a modified TIPS method using reagent grade polymers mixtures; polyacrylonitrile (PAN) and polyvinylpyridine-co-styrene (PVPS). Reaction conditions such as concentration, temperature and the solvents used were found to affect the morphology of the polymer materials formed. The use of low heat for polymer dissolution, near critical point polymer concentration and a miscible solvent/non-solvent pair in excess non-solvent were found to produce porous polymers. The macro-(meso-) porous materials were further used in metal adsorption/desorption studies and they were found to remove up to 80 % of Cu(II), Ag(I) and Au(III) from aqueous solution. Adsorption/desorption experiments were performed using the polymer monolith KSP1{(PAN : PVPS = 75 : 25 (w/w) in DMSO : H2O = 90 : 10(v/v)} and it showed excellent reusability adsorbing and desorbing up to 90 % of the metal ions in a series of five cycles. Ternary solutions for adsorption/desorption experiments were added in the order Cu(II), Ag(I) and Au(III). <![CDATA[<b>Effects of zinc precursor, basicity and temperature on the aqueous synthesis of ZnO nanocrystals</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100013&lng=pt&nrm=iso&tlng=pt The effects of the zinc salt precursors, the reaction temperature and the alkaline ratio b (b = [OH-]/[Zn2+]) on the aqueous synthesis of ZnO nanocrystals were investigated. Depending on the type of the zinc precursor, Zn5(OH)8CL/H2Oor Zn5(OH)8(NO3)2.2H2O lamellar phases were obtained at room temperature (20 °C) when the alkaline ratio is lower (0.5 < b < 1, 6 < pH <£ 6.4). When the reaction temperature increased to 95 °C, zinc hydroxide chloride monohydrate was obtained in one case whereas zinc oxide was formed in the other, and no lamellar phase of Zn5(OH)8(NO3)2.2H2O was obtained. Thermal decomposition of the two lamellar phases was carried out and mainly showed that Zn5(OH)8(NO3)2.2H2O was completely decomposed to ZnO when the annealed temperature reached ~250 °C while Zn5(OH)8CL/H2O was totally transformed to ZnO at about 400 °C, a higher comparative temperature that confirms the better thermal stability of the zinc hydroxide chloride monohydrate. <![CDATA[<b>Hyphenated LC-ICP-MS/ESI-MS identification of halogenated metabolites in South African marine ascidian extracts</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100014&lng=pt&nrm=iso&tlng=pt Extracts of 13 species of marine ascidian collected in Algoa Bay were analyzed by LC-ICP-MS/ESI-MS. This technique allows parallel analysis of the molecular species and the presence of certain elements. The LC-ICP-MS/ESI-MS technique was used to target iodinated metabolites in this study. Three ascidian species afforded the known 3,5-diiodo-4-methoxyphenethylamine (12), which was confirmedby the isolation of this metabolite from Aplidium monile. MS also suggested the presence of the known 3,5-dibromo-4-methoxyphenethylamine (10) and the new 3-bromo-5-iodo-4-methoxyphenethylamine (11)inthe A. monile extract. The presence of the known 3,5-dibromotetramethyltyrosine (21) and the new 3-iodotetramethyltyrosine (23) in extracts of an unidentified Didemnum species was similarly proposed from MS evidence. This is the first report of the occurrence of iodinated metabolites in South African marine invertebrates. <![CDATA[<b>Development and validation of an ecofriendly chemiluminescence method for the determination of citalopram in pharmaceutical preparations using Cu<sup>2</sup>+-grafted Oxidized multiwall carbon nanotubes</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100015&lng=pt&nrm=iso&tlng=pt A novel and sensitive chemiluminescence (CL) method was developed and validated for the determination of Citalopram in bulk dosage form and in pharmaceutical preparations. The method is based on the use of Cu²+-grafted oxidized multiwall carbon nanotubes (Cu/ox-MWCNTs). The weak CL signal arising from the reaction of an alkaline luminol-H2O2 system was significantly enhanced by the addition of citalopram in the presence of ox-MWCNTs/Cu²+. Furthermore, ox-MWCNTs/Cu²+ exhibited exceptional catalytic activity towards the oxidation of luminol in the luminol-H2O2 CL reaction. Multiwalled carbon nanotubes (MWCNTs) were characterized by scanning electron microscopy (SEM), which also showed the attachment of Cu²+ to MWCNTs. Various factors affecting CL intensity were carefully investigated and optimized for citalopram quantitation. The CL intensity was proportional to citalopram concentration in the range 0.2-8.0 mL-1, with a correlation coefficient of 0.996. The limit of detection (LOD) and limit of quantification were 2.29 X 10-5 mL-1 and 7.64 X 10-5 mL-1, respectively, and its reproducibility was satisfactory with a relative standard deviation (RSD) of 2.59 % (n = 5). The interference effects of common excipients were studied, and the developed method was effectively applied for the determination of citalopram in pure form and in pharmaceutical preparations. Percentage recoveries were calculated and ranged from 98.67 to 101.46 % for the pure form and from 97.38 to 101.72 % for pharmaceutical preparations. <![CDATA[<b>Development of an electrochemical nano-biosensor for rapid and sensitive diagnosis of bilharzia in Kenya</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100016&lng=pt&nrm=iso&tlng=pt Bilharzia, also known as schistosomiasis, is still affecting more than 250 million people, killing about 200 000 annually and leaving millions of others debilitated. Current diagnostic tools have extremely low validity and are not readily applicable for rapid diagnosis in rural and remote areas. In low-grade infections, microscopy, the most commonly used method, may have low sensitivity. For example, in suspected cases, up to five real sample specimens are recommended for increased sensitivity. The rise of nanotechnology has created the potential to significantly improve the current diagnostic approaches. Conjugating antibodies with nanoparticles pools the distinctive properties of the nanoparticles with the specificity and selectivity of the antibodies in the recognition of the antigen. This in return leads to a very versatile and specific mixed product with improved analytical signal which is important for fast, sensitive and real-time point-of-care diagnosis. In this work, we report the use of nanotechnology to develop a simple and sensitive nano-biosensor which consisted of a nano-strip with immobilized gold nanoparticles conjugated with bilharzia antibody, and demonstrated its potential for diagnosis of bilharzia antigen. A detection range of 1.13 X 10¹ ng mL-1 to 2.3 X 10³ ng mL-1 of bilharzia antigen in stool samples and with a limit of detection of 8.3887 X 10-2 ng mL-1 was attained, indicating the potential of the nano-biosensor to be used to detect bilharzia antigen in stool samples. <![CDATA[<b>Transition metal oxide supported on alumina catalysts: a comparative study for the hydrogenation of octanal</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100017&lng=pt&nrm=iso&tlng=pt Monometallic (10 wt.%) Co, Ni and Cu nanoparticles supported on alumina catalysts were prepared using an ultrasonic impreg-nation-cavitation method and characterized using ICPP XRD, physisorption, chemisorption and temperature programmed techniques. The copper catalyst showed higher metal dispersion and greater hydrogen and CO chemisorption capacity when compared to the nickel and cobalt catalysts. Hydrogenation of octanal carried out in a continuous flow high pressure fixed bed reactor showed that the rate of reaction and turnover number of octanol depended on the amount of hydrogen chemisorbed. The copper catalyst showed the lowest activation energy, as well as best catalytic activity. The Cu-Al catalyst which showed higher metal dispersion and low acidity, showed the highest selectivity towards octanol with no C24 acetal formation, when compared to the Ni-Al and Co-Al catalysts. <![CDATA[<b>Molecular Complexes of Boron Trifluoride with some Formyl Compounds, HCOX (X = H, CH<sub>3</sub>, NH<sub>2</sub>, OH, F): Effect of Substitution, and Extension to X = Li, BeH and BH<sub>2</sub></b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100018&lng=pt&nrm=iso&tlng=pt The complexes formed between boron trifluoride and formaldehyde, acetaldehyde, formamide, formic acid and formyl fluoride have been studied by means of ab initio calculations at the second order level of M0ller-Plesset perturbation theory (MP2), using Dunning's aug-cc-pVTZ basis sets. The structures, the interaction energies, the perturbations of the vibrational spectra and the charge transfers occurring on complexation, both of the BF3 and of the base moieties, have been determined and the variations in these properties have been rationalized in relation to the nature of the X fragments (X = H, CH3,NH2, OH, F). The calculations have been extended to include the putative complexes between BF3 and the presently unknown compounds HCOLi, HCOBeH and HCOBH2, in order to complete the range of formyl compound bases with heteroatoms across the whole of the first row of the periodic table. <![CDATA[<b>Effect of the Mechanical Treatment of Alumina on Thermal, Morphological and Dielectric Properties of LDPE/Al<sub>2</sub>O<sub>3</sub> Composites</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100019&lng=pt&nrm=iso&tlng=pt Composites of LDPE filled with different amounts of alumina Al2O3 were prepared using co-mixing technique and melt-mixing. This technique, which is easy, non-toxic and inexpensive, has been successfully used in our laboratory for different polyolefins/ metal oxides nanocomposites elaboration. Samples containing 0.5,1 and 2 wt% of alumina, were prepared by melt-mixing at 190 °C without any chemical treatment or coupling agent. The effect of alumina treatment was studied. The Al2O3 was first co-mixed with the stearic acid then added to the polymer. The stearic acid melts at 70 °C, thus ensuring the dispersion of the covered filler particles into the polymeric matrix, which leads to better experimental results. The morphological characterization was carried out by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal properties were investigated by thermogravimetric analysis (TGA). The electrical conductivity was also studied. The microstructure-properties relationships were also investigated. The composites prepared with the co-mixed Al2O3 were compared to those prepared with the neat Al2O3. The thermogravimetric (TGA) results showed an enhancement of 55 °C in the thermal stability for the LDPE/Al2O3 composition containing 1 wt% of treated Al2O3. The electrical conductivity results showed also an optimum value of 6.6.10-7 Ω-1 cm-1 for the same composition. <![CDATA[<b>Synthesis, Characterization and Antibacterial Properties of <i>N</i>,<i>N</i>'-Bis(4-dimethylaminobenzylidene)benzene-1,3-diamine as New Schiff Base Ligand and its Binuclear Zn(II), Cd(II) Complexes</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100020&lng=pt&nrm=iso&tlng=pt We synthesized a new Schiff base ligand by condensation reaction of 4-dimethylaminobenzaldehyde and 1,3-phenylenediamine. Treatment of this Schiff base ligand with Zinc(II) nitrate and Cadmium(II) nitrate in ethanol medium afforded the corresponding metal complexes. The synthesized ligand and complexes were characterized by their UV-Vis, FT-IR and ¹H-NMR, 13C-NMR spectral data and elemental analysis. The spectral data suggest an octahedral geometry for these complexes. Antibacterial activities of both synthesized free ligand and complexes were investigated against Escherichia coli, Staphylococcus aureus, and Bacillus subtilis bacteria. The complexes showed better antibacterial activity in comparison with that of the free ligand against selective bacteria. <![CDATA[<b>Electrochemical determination of 2,4-dichlorophenoxyacetic acid using bismuth film modified screen-printed carbon electrode</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100021&lng=pt&nrm=iso&tlng=pt In this work, the development of an electrochemical method for the determination of 2,4-dichlorophenoxy acetic acid (2,4-D) (indirectly by converting to its electroactive nitrated form) using a modified screen-printed carbon electrode with bismuth film is reported. The electrode modification has been done by a single potential step electrodeposition of bismuth film on screen-printed carbon electrodes. Under the optimized conditions, the nitrated 2,4-D showed a dynamic linear concentration range in pH 11 buffer from 11.1 to 74.3 um with regression coefficient (R) of 0.9988. The limits of detection and quantification were 3.15 um and 10.5 um, respectively. The proposed method offered higher sensitivity compared to bare screen-printed carbon electrodes. The modified electrode showed good reproducibility, repeatability, stability and recovery for the analysis of 2,4-D. The developed method was used for electroanalysis of 2,4-D in soil and water samples collected from Sito Kebele, Dedo district Jimma zone. <![CDATA[<b>Monitoring of So<sub>2</sub>, No<sub>x</sub> and Nh<sub>3</sub> emission from burning of solid wastes at Awotan and Lapite dumpsites, Ibadan, Nigeria</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100022&lng=pt&nrm=iso&tlng=pt Emission of gaseous pollutants from open dumpsites has been identified as a major source of air pollution in urban cities such as Ibadan, Nigeria. Air quality assessments at Awotan and Lapite dumpsites where burning of solid wastes occurs without adequate control were presented in this study. The open burning of solid wastes pose environmental challenges associated with the emission of SO2,NOx and NH3 whose adverse impact on humans in the vicinity of dumpsites is inevitable. The concentrations obtained for SO2,NOx and NH3 were in the range of 260-379 ug m-3; 354-470 ug m-3 and 590-907ug m-3, respectively, at Awotan dumpsite. The corresponding concentrations at Lapite dumpsite were 342-428 jug m-3; 521-741 jug m-3 and 1085-1374 jug m-3, respectively. Levels of SO2 and NOx exceeded the European Union and Nigeria national standard air quality limits. There is a need to develop better operating practices in terms of period and method of combustion of solid wastes at designated dumpsites in Ibadan. <![CDATA[<b>Synthesis, Antiplasmodial and Antitrypanosomal Evaluation of a Series of Novel 2-Oxoquinoline-based Thiosemicarbazone Derivatives</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100023&lng=pt&nrm=iso&tlng=pt Herein a series of novel thiosemicarbazones (TSCs) derived from 2-oxoquinoline scaffold is reported, and the target compounds have been successfully synthesized and characterized using standard spectroscopic techniques. The in vitro biological activities of synthesized molecules were evaluated against Plasmodium falciparum malaria parasites (strain 3D7), Trypanosoma brucei brucei parasites (strain 427) and HeLa cells. All the compounds displayed modest or no activity at a concentration of 20 μΜ and percentage viability of >50 % was often observed. Except for compound 9o, none of the final compounds exhibited cytotoxic effects against HeLa cells at 20 μΜ. <![CDATA[<b>Highly Sensitive Electrochemical Sensing Platform for the Detection of L-dopa Based on Electropolymerizing Glutathione Disulfide and Multi-walled Carbon Nanotube-modified Electrodes</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100024&lng=pt&nrm=iso&tlng=pt A facile sensing platform for the detection of L-dopa has been developed by electropolymerizing glutathione disulfide (PGSSG) on the surface of glass carbon electrodes (GCE) which were modified by multi-walled carbon nanotubes (MWCNTs). The electrochemical behaviour of the proposed electrodes were investigated via cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The morphology of the PGSSG and PGSSG/MWCNTs were characterized by scanning electron microscopy (SEM). Under the optimized experimental conditions, the sensing platform showed the linear response to L-Dopa in a range from 1.0 X 10-6 to 1.2X10-3 M with a detection limit of 3.3 X 10-7 M (S/N = 3). Moreover, with the merits of high sensitivity and selectivity, good stability and reproducibility, the sensor was successfully applied for the determination of L-dopa in a real sample. <![CDATA[<b>Synthesis, <i>in vitro </i>Cytotoxicity and Trypanocidal Evaluation of Novel 1,3,6-Substituted Non-fluoroquinolones</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0379-43502018000100025&lng=pt&nrm=iso&tlng=pt Sleeping sickness (trypanosomiasis) is a neglected tropical disease that affects mostly the poorest communities in sub-Saharan Africa. Toxic side effects associated with the use of current anti-trypanosomal drugs, which in some cases kill faster than the disease itself, necessitate the search for new drugs with better safety margins. To this effect, a small library bearing different substituents at position -1, -3, and -6 of the quinolone nucleus were synthesized and evaluated in vitro against HeLa cell lines and Trypanosoma brucei brucei for cytotoxicity and trypanocidal potentials, respectively. While most of these compounds showed no cytotoxic effect, they exhibited moderate to weak anti-trypanosomal activities. The SAR studies of this series provide new information worth considering in future exploration of the quinolone scaffold in search of more potent and safe trypanocidal agents.