Sodium dodecyl sulfate coated γ-alumina support modified by a new Schiff base for solid phase extraction and flame-AAS determination of lead and copper ions

A simple and fast approach for solid phase extraction is herein described, and used to determine trace amounts of Pb2+ and Cu2+ metal ions. The solid phase support is sodium dodecyl sulfate (SDS)-coated γ-alumina modified with bis(2-hydroxy acetophenone)-1,6-hexanediimine (BHAH) ligand. The adsorbed ions were stripped from the solid phase by 6 mL of 4 M nitric acid as eluent. The eluting solution was analyzed by flame atomic absorption spectrometry (FAAS). The sorption recovery of metal ions was investigated with regard to the effects of pH, amount of ligand, γ-alumina and surfactant and the amount and type of eluent. Complexation of BHAH with Pb2+ or Cu2+ ions was examined via spectrophotometry using the HypSpec program. The detection limit for Cu2+ was 7.9 µg L-1 with a relative standard deviation of 1.67%, while that for Pb2+ was 6.4 µg L-1 with a relative standard deviation of 1.64%. A preconcentration factor of 100 was achieved for these ions. The method was successfully applied to determine analyte concentrations in samples of liver, parsley, cabbage, and water.

Underpotential deposition and anodic stripping voltammetry at mesoporous microelectrodes

Using the technique of liquid crystal templating a series of high surface area mesoporous platinum microelectrodes was fabricated. The underpotential deposition of metal ions at such electrodes was found to be similar to that at conventional platinum electrodes. The phenomena of underpotential deposition, in combination with the intrinsic properties of mesoporous microelectrodes (i.e. a high surface area and efficient mass transport) was exploited for the purpose of anodic stripping voltammetry. In particular the underpotential deposition of Ag+, Pb2+ and Cu2+ ions was investigated and it was found that mesoporous microelectrodes were able to quantify the concentration of ions in solution down to the ppb range. The overall behaviour of the mesoporous electrodes was found to be superior to that of conventional microelectrodes and the effects of interference by surfactants were minimal.

Thermal behavior of Ca2+ and Cu2+ oxalates obtained by precipitation in homogeneous solution from dimethyl oxalate hydrolysis

Mixed calcium and copper oxalates, with different proportions of Ca2+ and Cu2+ ions, were precipitated by dimethyl oxalate hydrolysis in homogeneous solution. The compounds were evaluated by means of scanning electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetry (TG), and differential thermal analysis (DTA). The results suggested quantitative precipitation without solid solution formation. From the TG and DTA curves, it was possible to evaluate the Ca2+ ion proportion in the solid phase and to confirm the precipitation of the individual species.

Evaluation of a carbon paste electrode modified with organofunctionalised SBA-15 nanostructured silica in the simultaneous determination of divalent lead, copper and mercury ions

The performance of a carbon paste electrode (CPE) modified with SBA-15 nanostructured silica organofunctionalised with 2-benzothiazolethiol in the simultaneous determination of Pb(II), Cu(II) and Hg(II) ions in natural water and sugar cane spirit (cachaca) is described. Pb(II), Cu(II) and Hg(II) were pre-concentrated on the surface of the modified electrode by complexing with 2-benzothiazolethiol and reduced at a negative potential (-0.80 V). Then the reduced products were oxidised by DPASV procedure. The fact that three stripping peaks appeared on the voltammograms at the potentials of -0.48 V (Pb2+), -0.03 V (Cu2+) and +0.36 V (Hg2+) in relation to the SCE, demonstrates the possibility of simultaneous determination of Pb2+, Cu2+ and Hg2+. The best results were obtained under the following optimised conditions: 100 mV pulse amplitude, 3 min accumulation time, 25 mV s(-1) scan rate in phosphate solution pH 3.0. Using such parameters, calibration graphs were linear in the concentration ranges of 3.00-70.0 x 10(-7) mol L-1 (Pb2+), 8.00-100.0 X 10(-7) mol L-1 (Cu2+) and 2.00-10.0 x 10(-6) mol L-1 (Hg2+). Detection limits of 4.0 x 10(-8) mol L-1 (Pb2+), 2.0 x 10(-7) mol L-1 (Cu2+) and 4.0 x 10(-7) mol L-1 (Hg2+) were obtained at the signal noise ratio (SNR) of 3. The results indicate that this electrode is sensitive and effective for simultaneous determination of Pb2+, Cu2+ and Hg2+ in the analysed samples. (C) 2008 Published by Elsevier B.V.

The use of Langmuir-Blodgett films of a perylene derivative and polypyrrole in the detection of trace levels of Cu2+ ions

Langmuir films of a tetracarboxylic perylene derivative and polypyrrole display condensed surface pressure isotherms that are shifted when Cu2+ ions are added to the ultrapure water subphase. These films were transferred onto interdigitated gold electrodes leading to Y-type Langmuir-Blodgett (LB) films. The electrodes modified with 5-layer LB films were immersed into a flask with ultrapure water and water containing Cu2+ ions at concentrations ranging from mM to muM. Impedance measurements indicated a distinct electrical response for the two types of films. Although the materials chosen have no specificity for ionic metals, they can be combined for detecting trace levels of Cu2+, which may be exploited in water quality monitoring. (C) 2004 Elsevier B.V. All rights reserved.

Coordination networks of Cu2+ ions with 1,3-bis[2-(4-pyridyl)ethyl]benzene : strong structure-directing role of the counter ion (nitrate, acetate and sulphate), leading to clusters, sheets and chains

Date of Acceptance: 16/10/2015

Coordination networks of Cu2+ ions with 1,3-bis[2-(4-pyridyl)ethyl]benzene : strong structure-directing role of the counter ion (nitrate, acetate and sulphate), leading to clusters, sheets and chains

Date of Acceptance: 16/10/2015

Adsorption of immunoglobulin Y in supermacroporous continuous cryogel with immobilized Cu2+ ions

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electrochemical oxidation of acid black 210 dye on the boron-doped diamond electrode in the presence of phosphate ions: Effect of current density, pH, and chloride ions

The electrochemical oxidation of acid black 210 dye (AB-210) on the boron-doped diamond (BDD) was investigated under different pH conditions. The best performance for the AB-210 oxidation occurred in alkaline phosphate solution. This is probably due to oxidizing agents such as phosphate radicals and peroxodiphosphate ions, which can be electrochemically produced with good yields on the BDD anode, mainly in alkaline solution. Under this condition, the COD (chemical oxygen demand) removal was higher than that obtained from the model proposed by Comninellis. Electrolyses performed in phosphate buffer and in the presence of chloride ions resulted in faster COD and color removals in acid and neutral solutions, but in alkaline phosphate solution, a better performance in terms of TOC removal was obtained in the absence of chloride. Moreover, organochloride compounds were detected in all electrolyses performed in the presence of chloride. The AB-210 electrooxidation on BDD using phosphate as supporting electrolyte proved to be interesting since oxidizing species generated from phosphate ions were able to completely degrade the dye without producing organochloride compounds. (C) 2009 Elsevier Ltd. All rights reserved.

The requirement of zinc and calcium ions for functional MMP activity in demineralized dentin matrices

The progressive degradation of resin-dentin bonds is due, in part, to the slow degradation of collagen fibrils in the hybrid layer by endogenous matrix metalloproteinases (MMPs) of the dentin matrix. In in vitro durability studies, the storage medium composition might be important because the optimum activity of MMPs requires both zinc and calcium. Objective. This study evaluated the effect of different storage media on changes in matrix stiffness, loss of dry weight or solubilization of collagen from demineralized dentin beams incubated in vitro for up to 60 days. Methods. Dentin beams (1 mm x 2 mm x 6 mm) were completely demineralized in 10% phosphoric acid. After baseline measurements of dry mass and elastic modulus (E) (3-point bending, 15% strain) the beams were divided into 5 groups (n = 11/group) and incubated at 37 degrees C in either media containing both zinc and calcium designated as complete medium (CM), calcium-free medium, zinc-free medium, a doubled-zinc medium or water. Beams were retested at 3, 7, 14, 30, and 60 days of incubation. The incubation media was hydrolyzed with HCl for the quantitation of hydroxyproline (HOP) as an index of solubilization of collagen by MMPs. Data were analyzed using repeated measures of ANOVA. Results. Both the storage medium and the storage time showed significant effects on E, mass loss and HOP release (p < 0.05). The incubation in CM resulted in relatively rapid and significant (p < 0.05) decreases in stiffness, and increasing amounts of mass loss. The HOP content of the experimental media also increased with incubation time but was significantly lower (p < 0.05) than in the control CM medium, the recommended storage medium. Conclusions. The storage solutions used to age resin-dentin bonds should be buffered solutions that contain both calcium and zinc. The common use of water as an aging medium may underestimate the hydrolytic activity of endogenous dentin MMPs. (c) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Precious transition metals: the importance of Zn2+, Mn2+ and Cu2+ in the human pathogen Enterococcus faecalis

Dissertation presented to obtain the Ph.D degree in Biology

Observation of 2p3d(¹P°)→1s3d(¹Dᵉ) Radiative Transition in He-like Si, S, and Cl Ions

APS, Journals Phys. Rev. Lett., Volume 111, Issue 24

Characterization of molecular damage induced by UV photons and carbon ions on biomimetic heterostructures

The study of the effect of radiation on living tissues is a rather complex task to address mainly because they are made of a set of complex functional biological structures and interfaces. Particularly if one is looking for where damage is taking place in a first stage and what are the underlying reaction mechanisms. In this work a new approach is addressed to study the effect of radiation by making use of well identified molecular hetero-structures samples which mimic the biological environment. These were obtained by assembling onto a solid support deoxyribonucleic acid (DNA) and phospholipids together with a soft water-containing polyelectrolyte precursor in layered structures and by producing lipid layers at liquid/air interface with DNA as subphase. The effects of both ultraviolet (UV) radiation and carbon ions beams were systematically investigated in these heterostructures, namely damage on DNA by means vacuum ultraviolet (VUV), infrared (IR), X-Ray Photoelectron (XPS) and impedance spectroscopy. Experimental results revealed that UV affects furanose, PO2-, thymines, cytosines and adenines groups. The XPS spectrometry carried out on the samples allowed validate the VUV and IR results and to conclude that ionized phosphate groups, surrounded by the sodium counterions, congregate hydration water molecules which play a role of UV protection. The ac electrical conductivity measurements revealed that the DNA electrical conduction is arising from DNA chain electron hopping between base-pairs and phosphate groups, with the hopping distance equal to the distance between DNA base-pairs and is strongly dependent on UV radiation exposure, due loss of phosphate groups. Characterization of DNA samples exposed to a 4 keV C3+ ions beam revealed also carbon-oxygen bonds break, phosphate groups damage and formation of new species. Results from radiation induced damage carried out on biomimetic heterostructures having different compositions revealed that damage is dependent on sample composition, with respect to functional targeted groups and extent of damage. Conversely, LbL films of 1,2-dipalmitoyl-sn-Glycero-3-[Phospho-rac-(1-glycerol)] (Sodium Salt) (DPPG) liposomes, alternated with poly(allylamine hydrochloride) (PAH) revealed to be unaffected, even by prolonged UV irradiation exposure, in the absence of water molecules. However, DPPG molecules were damaged by the UV radiation in presence of water with cleavage of C-O, C=O and –PO2- bonds. Finally, the study of DNA interaction with the ionic lipids at liquid/air interfaces revealed that electrical charge of the lipid influences the interaction of phospholipid with DNA. In the presence of DNA in the subphase, the effects from UV irrladiation were seen to be smaller, which means that ionic products from biomolecules degradation stabilize the intact DPPG molecules. This mechanism may explain why UV irradiation does not cause immediate cell collapse, thus providing time for the cellular machinery to repair elements damaged by UV.

Dispersive liquid-liquid microextraction for the simultaneous separation of trace amounts of zinc and cadmium ions in water samples prior to flame atomic absorption spectrometry determination

In the proposed method, carbon tetrachloride and ethanol were used as extraction and dispersive solvents. Several factors that may be affected on the extraction process, such as extraction solvent, disperser solvent, the volume of extraction and disperser solvent, pH of the aqueous solution and extraction time were optimized. Under the optimal conditions, linearity was maintained between 1.0 ng mL-1 to 1.5 mg mL-1 for zinc and 1.0 ng mL-1 to 0.4 mg mL-1 for cadmium. The proposed method has been applied for determination of trace amount of zinc and cadmium in standard and water samples with satisfactory results.

Application of cloud point preconcentration and flame atomic absorption spectrometry for the determination of cadmium and zinc ions in urine, blood serum and water samples

A simple, sensitive and selective cloud point extraction procedure is described for the preconcentration and atomic absorption spectrometric determination of Zn2+ and Cd2+ ions in water and biological samples, after complexation with 3,3',3",3'"-tetraindolyl (terephthaloyl) dimethane (TTDM) in basic medium, using Triton X-114 as nonionic surfactant. Detection limits of 3.0 and 2.0 µg L-1 and quantification limits 10.0 and 7.0 µg L-1were obtained for Zn2+ and Cd2+ ions, respectively. Relative standard deviation was 2.9 and 3.3, and enrichment factors 23.9 and 25.6, for Zn2+ and Cd2+ ions, respectively. The method enabled determination of low levels of Zn2+ and Cd2+ ions in urine, blood serum and water samples.