Presence Of 8-hydroxyquinoline Research Articles

Chelate extraction of metal ions in aqueous/chloroform system based on molecular crowding environment

Abstract In this study, we propose a novel concept for the solvent extraction of metal ions (Co, Zn, and Pb) by mimicking a molecular crowding environment using dextran (Dex). The metal ions were extracted from the aqueous phase into the organic phase (chloroform) in the presence of 8-hydroxyquinoline (HQ). The extraction constant of the metal complex (Kex) increased with increasing Dex concentration (CDex) for all metal ions. When examining the dependence of CDex on the four equilibrium constants (distribution coefficient of HQ, acid dissociation of HQ, complexation constant of metal complex (β), and distribution coefficient of the metal complex) that contribute to Kex, only β increased with CDex. This suggests that an increase in, β, a parameter reflecting the molecular crowding effect, results in an increase in Kex. The increase in β was analyzed based on volume exclusion and osmotic pressure effects. The analytical model effectively explained the enhanced the complexation due to the increase in β and volume exclusion, whereas the osmotic pressure suppressed β. Consequently, we unveiled the effect of molecular crowding on the solvent extraction of metal ions for the first time.

Aqueous two-phase system based on benzethonium chloride and sodium dihexyl sulfosuccinate for extraction and ICP-OES determination of heavy metals

An aqueous two-phase system (ATPS) based on benzethonium chloride (BztCl) and sodium dihexyl sulfosuccinate (NaDHSS) was proposed for the first time for liquid-liquid microextraction of Cd(II), Co(II), Cu(II), Mn(II), Ni(II), and Pb(II) followed by ICP-OES determination. The mixture of cationic and anionic surfactants, BztCl and NaDHSS, showed liquid-liquid phase separation at the molar ratio of 1:1, and the total surfactant concentration of 0.01–0.2 mol L−1 forming ATPS that was investigated in the extraction process. The extraction efficiency for Cd(II), Co(II), Mn(II), Ni(II), and Pb(II) was nearly 100 %, and for Cu(II) – not lower than 88 % in the presence of 8-hydroxyquinoline as a complexing agent. The surfactant-rich phase containing analytes was subjected to back-extraction with 0.2 M HNO3 before ICP-OES measurements. The preconcentration in the proposed BztCl–NaDHSS–H2O ATPS for 30 s and the high degree of back-extraction, which was achieved in 1 min, significantly reduced the sample preparation time, matrix effects and provided low LODs in the range of 0.04–1.0 μg L−1, the preconcentration factor was 120. The analysis of a certified reference material sample of surface water and the real samples of tap, sea, and waste water verified the method accuracy.

Synthesis, biological evaluation and molecular docking studies of novel mixed-ligand Schiff base/8-hydroxyquinoline metal complexes

Five manufactured mixed ligands chelate of Schiff base (HL) in the presence of 8-hydroxyquinoline (HQ) with Chromium(III), Cobalt(II), Silver(I) tin(II), and mercury(II) was produced and described. The molecular structure of complexes was examined using physicochemical analysis, thermogravimetric analysis, and spectroscopic methods. Measurements of morphological properties confirm the nano-crystalline particles of the fabricated chelates. FT-IR analysis revealed that HL and HQ chelated with metal ions as NO bi-dentate ligands. The synthesized complexes have distorted octahedral (Cr(III) and Co(II)) and tetrahedral (Ag(I), Sn(II), and Hg(II) forms, according to magnetic and electronic spectrum data. Thermogravimetric (TG) analysis indicates that the formation complexes were stable. The antimicrobial and antiviral effectiveness of ligands and their metal complexes has also been investigated. The results indicated that the newly prepared complexes were greater in activity in contrast to their free ligands, and Studies on molecular docking have been performed out in order to determine the optimal engagement location as well as its inhibitory activity.

Synthesis, characterization, luminescence and NLO properties of heterotrinuclear MII-RuII-MII (M=Ni/Zn) complexes composed of coordination and organometallic sites

A new series of heterotrinuclear complexes of the type [Ru(dppm)2((CCC6H4CCC6H3 (O)HCNC6H4X)Ni(L'))2] (1a-c) and [Ru(dppm)2((CCC6H4CCC6H3(O)HCNC6H4X)Zn(L'))2] (2a-c) were prepared by the reaction of trans-[Ru(dppm)2(CCC6H4CCC6H3(OH)HCNC6H4X)2] with Ni(II)/Zn(II) ions in presence of 8-hydroxyquinoline. (where, X= Cl, Br, I; L'= 8-hydroxyquinoline) All the complexes were characterized by elemental analysis, FT-IR, 1H NMR, ESI-MS, UV–visible and thermogravimetric studies. The electrochemical properties of all the complexes indicate quasireversible redox behaviour corresponding to Ru(II)-Ru(III) and Ni(II)/ Ni(III) for 1a-c and Ru(II)/Ru(III) for 2a-c and are susceptible to variation of substituent group on ligand. All complexes show room temperature luminescence corresponding to π→π* intraligand charge transfer (ILCT) transition. The emission wavelength of the complexes is finely tuned by increasing π-conjugation and variation of substituent groups in the complexes. The second harmonic generation (SHG) efficiency of the complexes was measured by Kurtz-powder technique indicating that all complexes displayed the second harmonic generation (SHG) property.

Oxo transfer reaction: Dioxido and monooxidovanadium(V) complexes

A dioxidovanadium(V) complex of type [(LONOH−)(VO2)] (1) was isolated where LONOH2 is a tridentate ONO donor benzhydrazide ligand. 1 undergoes an oxo transfer reaction with triphenylphosphine in presence of 8-hydroxyquinoline (HQ) and affords a monooxidovanadium(V) complex of type [(LONO2−)(VO)(Q−)] (2). 1 and 2 were substantiated by elemental analyses, ESI-mass, IR, 1H NMR, 51V NMR and UV–vis spectra. The molecular geometries of 1 and 2 were authenticated by single crystal X−ray crystallography. UV–vis absorption spectra of 1 and 2 display bands respectively at 325 and 320 nm due to oxido → vanadium(V) charge transfer transitions. 1 exhibit an irreversible cathodic peak at −0.44 V whereas 2 displays a reversible cathodic wave at −0.60 V in cyclic voltammogram due to the VO3+/VO2+ redox couple.

Spectral, kinetic and thermodynamic studies of Pd (II) with Schiff base derived from L-asparagine and furfuraldehyde in the presence of 8-hydroxyquinoline

In this study, a Pd (II) complex of the type [Pd(L1)(L2)] (where L1: Schiff base derived from L-asparagine and furfuraldehyde; L2: 8-hydoxyquinoline) was synthesized and characterised using elemental analysis, magnetic moment, conductivity, ESI-MS, UV-Visible, FT-IR, 1H NMR, 13C NMR, XRD, SEM, EDX, and TG-DTA. The reaction conditions were determined as pH 7 and λ = 465 nm. When the reaction kinetics were examined, the rate formula was found to be v = k [Pd2+][L1]1/2[L2]1/2 and k = 2.51 × 10−3 lmol−1s−1. The activation energy (Ea) and Arrhenius constant (A) were calculated from the Arrhenius equation as 3.107 kJmol−1 and 5.38 × 10−5 s−1, respectively. Thermodynamic parameters, enthalpy, ∆H (kJmol−1), entropy, ∆S (Jmol−1), Gibbs free energy, ∆G (kJmol−1) and equilibrium constant, Ke, were determined at temperatures of 293.2, 313.2, 333.2 and 353.2 K. According to the thermodynamic parameters, the reaction was a non-spontaneous process. In addition, catalytic ability of the complex was investigated and it was observed that the complex could effectively catalyse epoxidation of cis-1,2-diphenylethylene with meta-chloroperoxybenzoic acid.

Pt(II) complex of Schiff base derived from L-phenylalanine and furfuraldehyde in the presence of 8-hydroxyquinoline: Structural analysis, composition of complex and biological activity

In the present study, we synthesized a Schiff base (L 1 ) derived from L-phenylalanine with furfuraldehyde and its Pt(II) complex ([Pt(L 1 )(L 2 )]: [Pt(N-(furfuralidene)phenylalanine)(8-hydroxyquinoline)]) in the presence of 8-hydroxyquinoline (L 2 ). The chemical structures of the synthesized Schiff base and Pt(II) complex were characterized using ESI-MS, UV–Visible, FT-IR, 1H NMR, 13C NMR, and powder-XRD spectroscopy. The surface morphologies and elemental composition were determined by SEM and EDX. Thermal analysis was performed with TG-DTA. Mole ratio of Meyer and Job methods were used for the composition of complexes. According to these methods, the ratio [Pt 2+ ] : [L 1 +L 2 ] was found to be 1 : 1. In addition, the antimicrobial activities of L 1 and the complex showed that the compounds have significant antibacterial and antifungal properties. They also show important cytotoxic effects against the growth of mouse embryo fibroblasts (MEF) and human prostate adenocarcinoma (Du145) cancer cells. L 1 , L 2 , and the Pt(II) complex also displayed effective antioxidant activity.

Spectroscopic characterization and XRD of some new metal complexes with dithranol in presence of 8-hydroxyquinoline

IN THE PRESENT work, dithranol (Dithr) reacts with Ni(II), Zn(II), Zr(IV), La(III), and Th(IV) in presence of heterocyclic ligand 8-hydroxyquinoline (8HQ) in acetone forming new mixed ligand complexes. The structures of the synthesized complexes were characterized by conventional techniques including melting point, molar conductivity, magnetic properties, elemental analyses, infrared, ultraviolet-visible, 1H nuclear magnetic resonance, and X-ray powder diffraction (XRD) spectra, as well as thermogravimetric (TG) and differential thermogravimetric (DTG) analyses. The molar conductance values of the metal complexes in dimethyl sulphoxide (DMSO) indicated that the complexes were found to be electrolytes with different ratios. The magnetic susceptibility measurements for Ni(II) complex is 3.1 BM with distorted octahedral geometry. TG/DTG studies confirmed the chemical formula for these complexes and established the thermal decomposition processes ended with the formation of metal oxide contaminated with carbon atom. The infrared spectra of the complexes showed shift for ν(O-H) and ν(C=N) in all complexes, which indicated the coordination of oxygen atom of phenolic group and nitrogen atom of pyridine ring of 8HQ with metal ions. X-ray powder diffraction analysis of the compounds showed that Dithr, 8HQ, and their metal complexes display crystalline peaks except Zr(IV) and La(III) complexes.

Colorimetric detection of chromium(VI) using graphene oxide nanoparticles acting as a peroxidase mimetic catalyst and 8-hydroxyquinoline as an inhibitor.

A method is described for the colorimetric determination of chromate [chromium(VI)]. It is based on the use of graphene oxide (GO) nanoparticles acting as a peroxidase mimic. A blue color is generated by oxidation of 3,3,5,5-tetramethylbenzidine by H2O2 which is catalyzed by GO. This color-forming reaction is prevented in the presence of 8-hydroxyquinoline (8-HQ). However, in the presence of Cr(VI), the blue color will be formed from TMBowing to the oxidation of the inhibitor8-HQ by Cr(VI). The color can be measured by a spectrophotometry (at 652nm) or detected visually. Under optimal experimental conditions, response is linear in the 50 to 430nM range of chromate concentration, and the limit of detection is 5.8nM (at S/N = 3). The assay is highly selective and was successfully applied to the determination of Cr(VI) in spiked water samples. Graphical abstract Schematic of the colorimetric assay for Cr(VI).TMB:3,3,5,5-tetramethylbenzidine.

On line automated system for the determination of Sb(V), Sb(III), thrimethyl antimony(v) and total antimony in soil employing multisyringe flow injection analysis coupled to HG-AFS

This paper proposes the use of a multisyringe flow injection analysis (MSFIA) system for inorganic antimony speciation analysis, trimethyl antimony(V) and determination of total antimony in soil samples using hydride generation atomic fluorescence spectrometry (HG-AFS). Total antimony has been determined after reduction of antimony(V) to antimony(III) using potassium iodide and ascorbic acid. For determination of total inorganic antimony the sample is percolated in a mini-column containing the Dowex 50W-X8 resin for retention of the organic species of antimony. Antimony(III) is quantified in presence of 8-hydroxyquinoline as masking agent for antimony(V) after an extraction step of the organic antimony species using the also same mini-column. The trimethyl antimony(V) content is found by difference between total antimony and total inorganic antimony. By other hand, antimony(V) is quantified by difference between total inorganic antimony and antimony(III). The analytical determinations were performed using sodium tetrahydroborate as reducing agent. The optimization step was performed using two-level full factorial design and Doehlert matrix involving the factors: hydrochloric acid and sodium tetrahydroborate concentrations and sample flow rate. The optimized experimental conditions allow the antimony determination utilizing the external calibration technique with limits of detection and quantification of 0.9 and 3.1ngg−1, respectively, and a precision expressed as relative standard deviation of 3.2% for an antimony solution of 5.0µgL−1. The method accuracy was confirmed by analysis of the soil certified reference material furnished from Sigma-Aldrich RTC. Additionally, addition/recovery tests were performed employing synthetic solutions prepared using trimethyl antimony(V), antimony(III), antimony(V) and five soil samples. The antimony extraction step was performed in a closed system using hydrochloric acid, ultrasonic radiation and controlled temperature. The method proposed was applied for analysis of thirteen soil samples collected in different sites of the Balearic Islands, Spain, and the results obtained varied from 19 to 46ngg−1 for trimethyl antimony(V) and from 113 to 215ngg−1 for total inorganic antimony. The concentrations obtained to antimony(V) were always higher than for antimony(III) in all the analyzed samples.

(Keynote) Local Electrochemical Impedance Spectroscopy: A Powerful Tool for Studying Corrosion Inhibition Mechanisms on 2024 Aluminum Alloy

Corrosion phenomena on aluminum alloy such as AA2024 are mainly linked to the local galvanic coupling between the intermetallic particles and the surrounding matrix [1]. To have a better understanding of the corrosion associated with copper-rich intermetallics, a simple system consisting of pure aluminum/pure copper (Al/Cu couple) has been previously considered [2]. From the beginning of immersion, increased cathodic activity related to oxygen reduction was observed at the Al/Cu interface. It was underlined that the local alkalinization of the electrolyte at the Al/Cu interface plays a key role in the degradation of the system. In a recent work devoted to the corrosion inhibition of the 2024 aluminum alloy, it was shown that mixing 8-hydroxyquinoline (8-HQ) and benzotriazole (BTA) led to a synergistic effect for the corrosion protection of the alloy [3]. This synergy was observed by conventional electrochemical measurements (current-voltage curves and global impedance spectroscopy). However, the electrode response corresponds to a surface-averaged measurement ascribable to the behavior of the whole electrode surface. Thus, local impedance measurements were performed on the model Al/Cu couple to analyze the role of the inhibitors on the galvanic coupling. It was shown that the galvanic coupling responsible for the corrosion process is strongly limited by mixing the two compounds which is not the case when the inhibitors are used separately. The synergistic effect was explained by the two different mechanisms by which BTA or 8-HQ inhibit corrosion: the action of BTA is mainly limited to the copper-rich intermetallic particles; 8-HQ acts on the aluminum matrix due to its chelating properties. In the present work, the same methodology was proposed to evaluate and to compare different compounds known for their effectiveness as corrosion inhibitors for the 2024 aluminum alloy [4-11]. The electrochemical measurements were carried out in a neutral NaCl solution, in presence of 8-hydroxyquinoline (8-HQ), benzotriazole (BTA), mercaptobenzothiazole (MBT) and a cerium salt. The compounds were used alone or as inhibitive mixtures and for various concentrations. Current-voltage curves and impedance measurements confirmed that the compounds are effective inhibitors for the aluminum alloy. Performing local electrochemical impedance measurements on the Al/Cu model allow to better understand the action of each compound on the galvanic coupling. The protective properties of the corrosion inhibitors were compared and discussed.

Synthesis, characterization and luminescence properties of azobenzene based heterobimetallic Ru(II)/M(II) (M = Ni and Zn) hybrid complexes composed of organometallic and coordination sites

Some azobenzene based heterobimetallic complexes of the type [Ni(RC6H4HCN(O)C6H3NNC6H4CCRu(dppe)2Cl)(L′)] (6a-c) and [Zn(RC6H4HCN(O)C6H3NNC6H4CCRu(dppe)2Cl)(L′)] (7a-c) have been prepared by the reaction of (RC6H4HCN(O)C6H3NNC6H4CCRu(dppe)2Cl) (3–5) with nickel acetate or zinc acetate in presence of 8-hydroxyquinoline (where L′ = 8-hydroxyquinoline, R = Cl, Br, I). All the complexes were characterized by elemental analyses, FTIR, UV–visible, 1H NMR, 31P NMR and ESI mass spectral studies. Thermal properties of 6a-c and 7a-c have been investigated using thermogravimetric analysis (TGA). The electrochemical behavior of the complexes reveals that all heterobimetallic complexes exhibit a quasireversible redox behavior corresponding to Ru(II)/Ru(III) and Ni(II)/Ni(III) for 6a-c and Ru(II)/Ru(III) for 7a-c. The room temperature luminescence is observed for all complexes which markedly depends on increasing electron-donating nature of the halide (I− < Br− < Cl−) in the complexes. The effect of different polarities of solvents on luminescence properties were examined and it is found that the excited state of all the complexes are stabilized and red shifted in their emission wavelength with increasing polarity of the solvents.

M(II) transfer across a liquid-liquid microinterface facilitated by a complex formation with 8-Hydroxyquinoline: Application to quantification of Pb(II), Cd(II) and Zn(II) alone or in mixture in effluents

For the first time, the assisted transfer of Pb(II) across a water/1,2-Dichloroethane (DCE) microinterface was investigated in the presence of 8-Hydroxyquinoline (named also oxine or 8-HQ) in the organic phase. A monocharged complex was formed in the aqueous phase and then transferred in the organic phase. A good relationship was obtained between currents and Pb(II) concentrations in the 10−4 to 5 10−3M range and 10−5 to 6 10−5M range using cyclic voltammetry and square wave voltammetry respectively. In presence of other heavy metals such as Cd(II) and Zn(II), only one electrochemical process is observed regardless of the mixture. Moreover, stationary currents increase in direct linear relation with the sum of M(II) concentrations added in water, allowing an overall detection of heavy metals. This result indicates that this method can be very interesting for monitoring all toxic metals in effluents. The limit of detection was found equal to 0.2ppm for lead. This value allows us to reach levels significant for industrial effluents, in comparison to the limits fixed by the French ministry of ecology for lead, cadmium and zinc to 0.5ppm, 0.2ppm and 2.0ppm respectively. This study highlights the real interest of devices based on a liquid-liquid microinterface.

A green preconcentration method for determination of cobalt and lead in fresh surface and waste water samples prior to flame atomic absorption spectrometry.

Cloud point extraction (CPE) has been used for the preconcentration and simultaneous determination of cobalt (Co) and lead (Pb) in fresh and wastewater samples. The extraction of analytes from aqueous samples was performed in the presence of 8-hydroxyquinoline (oxine) as a chelating agent and Triton X-114 as a nonionic surfactant. Experiments were conducted to assess the effect of different chemical variables such as pH, amounts of reagents (oxine and Triton X-114), temperature, incubation time, and sample volume. After phase separation, based on the cloud point, the surfactant-rich phase was diluted with acidic ethanol prior to its analysis by the flame atomic absorption spectrometry (FAAS). The enhancement factors 70 and 50 with detection limits of 0.26 μg L−1 and 0.44 μg L−1 were obtained for Co and Pb, respectively. In order to validate the developed method, a certified reference material (SRM 1643e) was analyzed and the determined values obtained were in a good agreement with the certified values. The proposed method was applied successfully to the determination of Co and Pb in a fresh surface and waste water sample.

Gold Nanoparticle/Polymer Interfaces: All Atom Structures from Molecular Dynamics Simulations

Molecular dynamics simulations have been performed to obtain detailed all-atom models of the interface between polystyrene (PS) and gold nanoparticles. Considering their relevance in the memory technology, systems containing gold nanoparticle included in PS polymer melts also in the presence of 8-hydroxyquinoline (8-HQ) molecules have been studied. Four different systems, including a coated or a noncoated nanoparticle, have been compared. Calculated radial density profiles show that the presence of noncoated nanoparticles in a polymer melt causes an ordering of polymer chains. A similar ordering behavior is found for the 8-HQ molecule. In the presence of a coated gold nanoparticle, calculated radial density profiles show much less order. When 8-HQ is present, this molecule is closer to the nanoparticle surface and when in contact with a coated nanoparticle it shows a partial penetration into the thiols layer. The molecular description obtained from simulations supports some of the hypothesis made on the basis of the experimental behavior of nonvolatile memory devices.

Synthesis, spectral studies, and antimicrobial activity of binary and ternary Cu(II), Ni(II), and Fe(III) complexes of new hexadentate Schiff bases derived from 4,6-diacetylresorcinol and amino acids

Two new hexadentate N2O4 donor Schiff bases, H4L1 and H4L2, were synthesized by condensation of 4,6-diacetylresorcinol with glycine and alanine, respectively. The structures of the ligands were elucidated by elemental analyses, IR, 1H NMR, electronic, and mass spectra. Reactions of the Schiff bases with copper(II), nickel(II), and iron(III) nitrates in 1 : 2 molar ratio gave binuclear metal complexes and, in the presence of 8-hydroxyquinoline (8-HQ) or 1,10-phenanthroline (Phen) as secondary ligands (L′), mixed-ligand complexes in two molar ratios 1 : 2 : 2 and 1 : 2 : 1 (L1/L2 : M : L′). The complexes were characterized by elemental and thermal analyses, IR, electronic, mass, and ESR spectral studies, as well as conductivity and magnetic susceptibility measurements. The spectroscopic data reveal that the Schiff-base ligands were dibasic or tetrabasic hexadentate ligands. The coordination sites with the metal ions are two azomethine nitrogens, two oxygens of phenolic groups, and two oxygens of carboxylic groups. Copper(II) complexes were octahedral and square planar while nickel(II) and iron(III) complexes were octahedral. The Schiff bases, H4L1 and H4L2, and some of their metal complexes showed antibacterial activity towards Gram-positive (Staphylococcus aureus and Streptococcus pyogenes) and Gram-negative (Pseudomonas fluorescens and Pseudomonas phaseolicola) bacteria and antifungal activity towards the fungi Fusarium oxysporium and Aspergillus fumigatus.

Synthesis, characterization and evaluation of ionic-imprinted polymers for solid-phase extraction of nickel from seawater

Several nickel ion imprinted polymers were prepared via precipitation polymerization using 4-vinylpyridine or 2-(diethylamino) ethyl methacrylate as monomers (vinylated reagents) and a cross-linking agent divinylbenzene in the presence of nickel(II) alone or nickel(II) and 8-hydroxyquinoline (non-vinylated reagent). For all cases, 2,2′-azobisisobutyronitrile (AIBN) was used as an initiator and an acetonitrile/toluene (3:1) mixture was chosen as a porogen. After packing the polymer particles into empty SPE cartridges, nickel(II) ions were removed by washing with 50 mL of 2.0 M nitric acid. Characterization of the polymer particles has been carried out by scanning electron microscopy, energy dispersive X-ray fluorescence and elemental analysis. The best nickel imprinting properties were given by polymers synthesized in the presence of 8-hydroxyquinoline and 2-(diethylamino) ethyl methacrylate as a monomer. The optimum pH for quantitative nickel retention was 8.5 ± 0.5, while elution was completed with 2.5 mL of 2.0 M nitric acid. When using polymer masses of 300 mg, sample volumes until 250 mL can be passed through the cartridges without reaching the breakthrough volume. Therefore, a pre-concentration factor of 100 has been reached when eluting with 2.5 mL of the elution solution. Electrothermal atomic absorption spectrometry has been used as a detector for nickel determination. The limit of detection of the method was 0.050 μg L −1 (pre-concentration factor of 100), while the relative standard deviation for eleven replicates was 6%. Accuracy of the method was assessed by analyzing different certified reference materials: SLEW-3 (estuarine water) and TM-23.3 and TM-24 (lake water).

Effect of ultraviolet and visible radiation on iron lability in boreal and artificial waters

Dialysis experiments were used to assess lability of Fe in boreal stream waters as well as synthetic solutions with the chelators ethylenediaminetetraacetic acid (EDTA) and 8-hydroxyquinoline in Bold Basal Medium (BBM). It was hypothesized that irradiation (UV and visible) of organic-Fe complexes would result in enhanced movement of Fe across a dialysis membrane with a 100Da molecular weight cutoff. Irradiation of boreal stream waters at pH 4 with UV plus visible radiation consistently resulted in increased Fe concentrations in the dialysis tubing containing 1.0 mM deferoxamine (a chelator)compared to the dark controls. Significant Fe lability occurred in the absence of UVB and UVA when stream water was exposed to visible wavelengths between 400 and 700 nm, but not when exposed to 550–700 nm. Irradiation of BBM media with EDTA with and without UVA under visible light increased lability of Fe and Co but not Mn, Cu or Zn, relative to dark controls indicating that EDTA binding strength is light sensitive for some metals. In contrast, Fe lability in the presence of 8-hydroxyquinoline was not significantly affected by UVA plus visible light relative to a dark control. If lability is used an indicator of biologically availability, then light intensity and spectral quality likely affects the supply rate of biologically available Fe and perhaps other metals in situ. Light conditions may also affect supply rates of biologically available metals in algal cultures, depending on the chelator used.

Biocidal activity of some Mannich base cationic derivatives

A novel series of cationic surfactants was prepared based on Mannich base (produced from the condensation of piperidine and/or morpholine as secondary amine and paraformaldehyde in the presence of 8-hydroxyquinoline). The chemical structures of the synthesized cationic surfactants were confirmed using elemental analyses, FTIR spectroscopy and 1H NMR. Surface activities of the prepared surfactants were measured including: surface tension ( γ), critical micelle concentration (CMC), effectiveness ( π CMC), efficiency (Pc 20), maximum surface excess ( Γ max), minimum surface area ( A min), interfacial tension ( γ IT), emulsification power and foaming power at 25 °C. The structural influences on their surface activities and adsorption free energy were discussed. The synthesized cationic surfactants were evaluated for their biocidal activity towards Gram +ve bacteria ( Staph. Cocu., Bacillus), Gram −ve bacteria ( Salmonella, E. coli), fungi ( A. terrus., A. flav.) and yeast ( Candida) at 1.0, 2.5 and 5.0 mg/mL, respectively. The target compounds showed good inhibition towards Gram +ve bacteria, Gram −ve bacteria and yeast. Meanwhile, excellent fungicidal results were obtained against the various types of fungi under investigation.

The synergistic inhibition between 8-hydroxyquinoline and chloride ion for the corrosion of cold rolled steel in 0.5 M sulfuric acid

The corrosion inhibition of cold rolled steel in 0.5 M sulfuric acid in the presence of 8-hydroxyquinoline and sodium chloride (NaCl) has been investigated by using weight loss and electrochemical techniques. The inhibition efficiency increases with increasing concentration of 8-hydroxyquinoline at the same temperature, but decreases with increasing temperature studied. A synergistic effect exists when 8-hydroxyquinoline and chloride ions are used together to prevent cold rolled steel corrosion in 0.5 M sulfuric acid at every experimental temperature. The polarization curves show that 8-hydroxyquinoline is a cathodic inhibitor, while the complex of 8-hydroxyquinoline and NaCl is a mixed-type inhibitor. The experimental results suggested that the presence of chloride ions in the solution stabilizes the adsorption of 8-hydroxyquinoline molecules on the metal surface and improved the inhibition efficiency of 8-hydroxyquinoline. The adsorption of single 8-hydroxyquinoline follows the Temkin adsorption isotherm, but the complex accords with the Langmuir adsorption isotherm. Some thermodynamic parameters such as adsorption heat, adsorption entropy and adsorption free energy have been calculated by employing thermodynamic equations. Kinetic parameters such as apparent activation energy and pre-exponential factor have been calculated and discussed.