[Show abstract][Hide abstract] ABSTRACT: We report here the design of a novel immunosensor and its application for celiac disease diagnosis, based on electrogenerated chemiluminescence (ECL) readout and using membrane-templated gold nanoelectrode ensembles (NEEs) as a detection platform. An original sensing strategy is presented by segregating spatially the initial electrochemical reaction and the location of the immobilized biomolecules where ECL is finally emitted. The recognition scaffold is the following: tissue transglutaminase (tTG) is immobilized as a capturing agent on the polycarbonate (PC) surface of the track-etched templating membrane. It captures the target tissue transglutaminase antibody (anti-tTG), and finally allows the immobilization of a streptavidin-modified ruthenium-based ECL label via reaction with a suitable biotinylated secondary antibody. The application of an oxidizing potential in a tri-n-propylamine (TPrA) solution generates an intense and sharp ECL signal, suitable for analytical purposes. Voltammetric and ECL analyses evidenced that the ruthenium complex is not oxidized directly at the surface of the nanoelectrodes, instead ECL is generated only following the TPrA oxidation which produces the TPrA●+ and TPrA● radicals. With NEEs operating under total overlap diffusion conditions, high local fluxes of these reactive radicals are produced by the nanoelectrodes in the immediate vicinity of the ECL labels, so that they efficiently generate the ECL signal. The radicals can diffuse over the short distance (< 200 nm) required for their reaction with the 〖Ru(bpy)〗_3^(2+) label. In addition, the ECL emission is obtained by applying a potential of 0.88 V vs Ag/AgCl, which is about 0.3 V lower than when ECL is initiated by the electrochemical oxidation of 〖Ru(bpy)〗_3^(2+) (i.e. 1.2 V vs. Ag/AgCl). The immunosensor provides ECL signals which scale with anti-tTG concentration with a linearity range between 1.5 ng.mL-1 and 10 µg.mL-1 and a detection limit of 0.5 ng.mL-1. The sensor was finally applied to the analysis of anti-tTG in human serum samples, showing to be suitable to discriminate between healthy and celiac patients.
Full-text · Article · Nov 2015 · Analytical Chemistry
[Show abstract][Hide abstract] ABSTRACT: In this study we proposed electrochemical behavior and determination of baicalein, main active flavonoid from Scutellaria baicalensis, using boron doped diamond electrode. In Britton–Robinson buffer solution, pH 2, baicalein provides two single oval shape oxidation peaks at + 0.5 V/Ag–AgCl and a second one at + 0.8 V/Ag–AgCl. For quantification of baicalein square wave voltammetry was used. Under optimized parameters calibration curve was linear over the range 1–95 μM with detection limit of 0.26 μM. After eight successful measurements repeatability was 3.7%. Proposed method was applied for determination of baicalein in real samples with excellent recovery. The influence of the most common interferences, biomolecules presented in urine was investigated. The developed approach could be beneficial in analysis of widely used flavonoid in biological samples.
No preview · Article · Sep 2015 · Diamond and Related Materials
[Show abstract][Hide abstract] ABSTRACT: Experimental results of non-thermal plasma (NTP) utilization for degradation of 4-chlorphenol (4CP) with screening of toxicity were presented in this study. Degradation of 4CP was tested in the presence of homogeneous catalysts: hydrogen peroxide (H2O2) and iron (II) (Fe2+). The rate of degradation through eight consecutive passes of the 4CP solution in the NTP reactor was considered. Products of degradation as organic acids (acetic, formic or oxalic acid) and chloride were quantified using ion chromatography (IC). Artemia salina was used for the toxicity screening assay in order to estimate the potential and consequences of NTP reactor application in water treatment. The measured concentration of 4CP and degradation products confirmed very efficient removal of these substances from the water during the NTP treatment with the addition of a catalyst. Concerning bioassay, a significant difference in toxicity was determined between initial solution of 4CP in comparison with the solution exposed to catalytic NTP treatment.
[Show abstract][Hide abstract] ABSTRACT: Composite material Zr-doped TiO2, suitable for the removal of arsenic from water, was synthetized with fast and simple microwave-hydrothermal method. Obtained material, Zr-TiO2, had uniform size and composition with zirconium ions incorporated into crystal structure of titanium dioxide. Synthetized composite material had large specific surface area and well-developed micropore and mesopore structure that was responsible for fast adsorption of As(III) and As(V) from water. The influence of pH on the adsorption capacity of arsenic was studied. The kinetics and isotherm experiments were also performed. The treatment of natural water sample containing high concentration of arsenic with composite material Zr-TiO2 was efficient. The concentration of arsenic was reduced to the value recommended by WHO.
Full-text · Article · Aug 2015 · Environmental Science and Pollution Research
[Show abstract][Hide abstract] ABSTRACT: In the present study, BCR sequential extraction procedure was introduced to assess mobility of heavy metals (HMs) in agricultural soils along the Ibar River Valley in the historically industrial region. Furthermore, the potato samples grown on these soils were estimated for their bioaccumulation ability. The concentrations of Pb, Zn, Cd, Ni, Cr, and Cu in soil and plant samples were determined by the ICP-OES method. The results indicated that industrial Pb/Zn production over the years significantly increased not only the total concentrations of HMs in the soil, but also their mobile and potentially bioavailable amounts. The order of the bioconcentration capacity in potato samples were Cu>Zn>Cd>Pb>Ni>Cr.
[Show abstract][Hide abstract] ABSTRACT: Among luminescence techniques, electrogenerated chemiluminescence (ECL) provides a unique level of manipulation of the luminescent process by controlling the electrochemical trigger. Despite its attractiveness, ECL is by essence a 2D process where light emission is strictly confined to the electrode surface. To overcome this intrinsic limitation, we added a new spatial dimension to the ECL process by generating 3D ECL at the level of millions of micro-emitters dispersed in solution. Each single object is addressed remotely by bipolar electrochemistry and they generate collectively the luminescence in the bulk. Therefore, the entire volume of the solution produces light. To illustrate the generality of this concept, we extended it to a suspension of multi-walled carbon nanotubes where each one acts as an individual ECL nano-emitter. This approach enables a change of paradigm by switching from a surface-limited process to 3D electrogenerated light emission.
[Show abstract][Hide abstract] ABSTRACT: We studied the effect of liming and P fertilization of extremely acid soil (accidently acidified by sulfidic mining waste) on P availability and the subsequent adaptive responses of wheat roots. The wheat plants were grown in rhizoboxes allowing precise sampling of rhizosphere and bulk soil for sequential extraction of P fractions and determination of exchangeable Al. Root exudates were collected by pieces of paper for electrophoresis and subjected to HPLC analysis. Expression of organic anions and Pi transporter genes was analyzed by a real-time quantitative PCR. The concomitant application of lime with P fertilization increased the concentrations of plant-available P fractions in both rhizosphere and bulk compartments. The applied soil amendments strongly affected plant growth, biomass partitioning and shoot P accumulation. Liming enhanced root exudation of citrate in P unfertilized plants, while the high malate efflux was maintained until both P deficiency and Al toxicity were eliminated by the amendments. We showed the importance of liming for recovering of P acquisition potential of wheat roots, which can be strongly impaired in acid soils. Our results clearly demonstrated that P-deficient roots not subjected to Al stress in the limed soil can maintain high efflux of malate and even increase efflux of citrate along with the enhanced expression of related anion transporters (TaMATE1 and TaALMT1).
No preview · Article · Mar 2015 · Biology and Fertility of Soils
[Show abstract][Hide abstract] ABSTRACT: The objectives of this study were to determine the concentrations of Pb, Cd, As, Cr, Cu, Co, Ni, Zn, Ba, Fe, Al and Ag in Erigeron canadensis L. growing on fly ash landfill of power plant "Kolubara", Serbia. The content of each element was determined in every part of plant separately (root, stalk and inflorescence) and correlated with the content of elements in each phase of sequential extraction of fly ash. In order to ambiguously select the factors that are able to decidedly characterize the particular part of plant, principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were performed. The bioconcentration factors and translocation factors for each metal were calculated in order to determine the feasibility of the use of plant E. canadensis L. for phytoremediation purpose. There were strong positive correlations between metals in every part of plant samples, and metals from pseudo total form of sequential extraction indicate that the bioavailability of elements in fly ash is similarly correlated with total form. Retained Al, Fe, Cr and Co in the root indicate its suitability for phytostabilization. This plant takes up Cd and Zn from the soil (bioconcentration factors (BCFs) greater than 1), transporting them through the stalk into the inflorescence (translocation factors (TFs) higher than 1). Regarding its dominance in vegetation cover and abundance, E. canadensis L. can be considered adequate for phytoextraction of Cd and Zn from coal ash landfills at Kolubara.
Full-text · Article · Mar 2015 · Environmental Science and Pollution Research
[Show abstract][Hide abstract] ABSTRACT: A novel efficient differential pulse voltammetric (DPV) method for determination gallic acid (GA) was developed by using an electrochemical sensor based on [Cu2tpmc](ClO4)4 immobilized in PVC matrix and coated on graphite (CGE) or classy carbon rod (CGCE). The proposed method is based on the gallic acid oxidation process at formed [Cu2tpmcGA]3+ complex at the electrode surface. The complexation was explored by molecular modeling and DFT calculations. Voltammograms for both sensors, recorded in a HNO3 as a supporting electrolyte at pH 2 and measured in 2.5×10−7 to 1.0×10−4 M of GA, resulted with two linear calibration curves (for higher and lower GA concentration range). The detection limit at CGE was 1.48×10−7 M, while at CGCE was 4.6×10−6 M. CGE was successfully applied for the determination of the antioxidant capacity based on GA equivalents for white, rosé and red wine samples.
[Show abstract][Hide abstract] ABSTRACT: This paper describes determination of trace level of copper ions on a new type of modified glassy carbon paste electrode based on addition of different amount of Co-ferrites in glassy carbon paste (CoFeMGCPE). Co-ferrite nanoparticles with different amount of cobalt were synthesized and characterized using scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). A significant increase in current was achieved by introducing modifier in composition of the electrode in comparison with the bare glassy carbon paste electrode. Electrochemical parameters such as percentage of modifier, accumulation time and potential, pH and the optimized amount of cobalt in the ferrites were determined. The best voltammetric response was observed for Co0.5Fe0.5Fe2O4 when percentage of modifier was 3%. In acetate buffer solution, pH 4.5, thus prepared electrode displays selective detection toward copper ions, detection limit of 96 nM and it was successfully applied for the determination of copper ions in natural water samples, with satisfactory recovery.
No preview · Article · Jan 2015 · Analytical and Bioanalytical Electrochemistry
[Show abstract][Hide abstract] ABSTRACT: The aim of this paper was the development and optimization of an electrochemical method for the degradation of two triketone herbicides, mesotrione and sulcotrione, in a two-electrode undivided electrochemical cell equipped with commercially available, non-modified, electrode materials. The electrochemical parameters studied included five different electrode systems (Zr/Pt, Pd/Pt, C/Pt, Nb/Pt and Ti/Pt), current densities (27.66, 55.33, …, 110.66 mA·cm-2) and pH values (3, 7 and 9) in 0.05 M sodium sulfate as supporting electrolyte. The electrical energy consumption and chemical oxygen demand were calculated for optimal conditions. The degradation efficiency was determined by high performance liquid chromatography equipped with a diode array detector, while the degradation products for both pesticides were identified and compared by UHPLC-mass spectrometry. The results could lead to an accurate estimate of their effect on the environment. A real water sample was used to study the influence of organic matter on pesticide degradation. Based on the results obtained the electrochemical treatment could be used for the successful removal of triketone herbicides from contaminated water.
Full-text · Article · Dec 2014 · CLEAN - Soil Air Water
[Show abstract][Hide abstract] ABSTRACT: Bentonite clay rich in smectite clay mineral from seldom investigated locality Mečji Do (MD) in Serbia was modified. The organomodification was performed with different loadings of benzyltrimethylammonium (BTMA) cation. The characterization of clay-based samples was performed, including XRD, FTIR and chemical and textural analysis. Electrochemical investigation was performed on a glassy carbon electrode (GCE) support with thin film of homogenously deposited either Na-enriched or one of organomodified clays forming composite electrodes. The behavior of the composite electrodes in the electrooxidation of p-nitrophenol (p-NP) in acidic media was analyzed using multisweep cyclic voltammetry. Oxidation of p-NP occurred at 1.2 V vs. Ag/AgCl for all investigated electrodes. The results indicate that the incorporation of BTMA cations into smectite enhanced the electrode stability toward the electrooxidation of p-NP in comparison to bare GCE and composite electrode based on Na-enriched clay. The current density for the p-NP oxidation wave slightly decreased with the increase of BTMA loading. On the other hand the electrode stability was significantly improved with the increase of BTMA loading.
[Show abstract][Hide abstract] ABSTRACT: Elevated concentrations of arsenic in groundwater, which is used as a source for drinking water, is a worldwide problem. Use of TiO2 and iron doped TiO2 synthesized by a microwave-assisted hydrothermal method for As(III) and As(V) removal were examined. Synthesized sorbents were characterized with XRD and nitrogen physisorption. Synthesized sorbents have predominantly anatase structure, and no peaks for iron could be observed. Doping of iron increases the surface area of synthesized sorbents. Sorption experiments show that increase of iron in sorbents increases the sorption capacity for As(III) and As(V). Increase of pH from 3 to 11 has no influence on As(III) sorption but decreases the sorption of As(V). Batch isotherm studies were performed to determine the binding capacities of As(III) and As(V). As(III) followed the Freundlich isotherm model, while for As(V) a better fit was with the Langmuir isotherm. The results of competition of SO42– and PO43– anions on adsorption of As(III) indicated that both anions reduced substantially the efficiency of adsorption on both adsorbents while for As(V) only the presence of PO43– anion interfered with adsorption. Testing 10Fe/TiO2 sorbent with arsenic contaminated natural water showed that this material could be used for removal of arsenic to the level recommended by WHO without pretreatment.
No preview · Article · Jul 2014 · Industrial & Engineering Chemistry Research
[Show abstract][Hide abstract] ABSTRACT: This paper describes the preparation of a new sensor based on Zn-ferrite modified glassy carbon paste electrode and its electrochemical application for the determination of trace Cd(II) ions in waste waters using differential pulse anodic stripping voltammetry (DPASV). Different Zn/Ni ferrite nanoparticles were synthesized and characterized using scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). The prepared ferrite nanoparticles were used for the preparation of Zn-ferrite-modified glassy carbon paste electrode (ZnMGCPE) for determination of Cd(II) at nanomolar levels in waste water at pH 5. The different parameters such as conditions of preparation, Zn2+/Ni2+/Fe2+ ratio and electrochemical parameters, percentage of modifier, accumulation time, pH and accumulation potential were investigated. Besides, interference measurements were also evaluated under optimized parameters. The best voltammetric response was observed for ZnFe2O4 modifier, when the percentage of modifier was 3 %, accumulation time 9 min, pH of supporting electrolyte 5 and accumulation potential −1.05 V. Thus prepared electrode displays excellent response to Cd(II) with a detection limit of 0.38 ppb, and selective detection toward Cd(II) was achieved.
[Show abstract][Hide abstract] ABSTRACT: In power plant, coal ash obtained by combustion is mixed with river water and transported to the dump. Sequential extraction was used in order to assess pollution caused by leaching of elements during ash transport through the pipeline and in the storage (cassettes). A total of 80 samples of filter ash as well as the ash from active (currently filled) and passive (previously filled) cassettes were studied. Samples were extracted with distilled water, ammonium acetate, ammonium oxalate/oxalic acid, acidic solution of hydrogen-peroxide, and a hydrochloric acid. Concentrations of the several elements (Al, As, Cd, Co, Cu, Cr, Fe, Ba, Ca, Mg, Ni, Pb, and Zn) in all extracts were determined by inductively coupled plasma atomic emission spectrometry. Pattern recognition method was carried out in order to provide better understanding of the nature of distribution of elements according to their origins. Results indicate possible leaching of As, Ca, Cd, Cu, Zn, and Pb. Among these elements As, Cd, and Pb are toxicologically the most important but they were not present in the first two phases with the exception of As. The leaching could be destructive and cause negative effects on plants, water pollution, and damage to some life forms.
[Show abstract][Hide abstract] ABSTRACT: An electrochemiluminescent (ECL) swimmer driven by bipolar electrochemistry is reported for enzymatic glucose sensing. The chemo-mechanical motion is induced by localized hydrogen bubble generation. The concomitant oxidation of the luminophore and of the enzymatically-produced NADH leads to ECL emission with a direct glucose-dependent light intensity. We demonstrate herein the local sensing and reporting of glucose in a concentration gradient explored by the ECL swimmer. Such a dynamic sensing approach combines in a synergetic way the wireless propulsion with the enzymatic selectivity using ECL as a readout method at the level of moving objects.
Full-text · Article · Jun 2014 · Chemical Communications
[Show abstract][Hide abstract] ABSTRACT: Microwave-hydrothermal method was used for synthesis of TiO2 and TiO2 doped with zirconium. Method was fast and simple and adsorbents were used for removal of As(III) and As(V) from aqueous solutions. The adsorbents were characterized by BET surface area measurements and powder XRD. Experiments showed that TiO2 doped with 10% of Zr using microwave-hydrothermal method have greater specific surface area and total pore volume in comparison with TiO2 synthetized with the same method. Better removal with doped adsorbent was obtained for both, As(III) and As(V). Further experiments were carried out with Zr doped TiO2 sorbent in order to examine kinetic of adsorption, influence of pH and effect of common anions present in natural waters.
Full-text · Article · Jun 2014 · Journal of Saudi Chemical Society
[Show abstract][Hide abstract] ABSTRACT: The remarkable characteristics of electrogenerated chemiluminescence (ECL) as a readout method are successfully exploited in numerous microbead-based immunoassays. However there is still a lack of understanding of the extremely high sensitivity of such ECL bioassays. Here the mechanisms of the reaction of the Ru(bpy)(3)(2+) luminophore with two efficient co-reactants (TPrA or DBAE) were investigated by mapping the ECL reactivity at the level of single Ru(bpy)(3)(2+)-functionalized beads. Micrometric non-conductive beads were decorated with the ruthenium label via a sandwich immunoassay or via a peptide bond. Mapping the ECL reactivity on one bead demonstrates the generation of the excited state at a micrometric distance from the electrode by reaction of surface-confined Ru(bpy)(3)(2+) with diffusing TPrA radicals. The signature of the TPAc center dot+ lifetime is obtained from the ECL profile. Unlike the reaction with Ru(bpy)(3)(2+) in solution, DBAE generates very low ECL intensity in the bead-based format suggesting more unstable radical intermediates. The 3D imaging approach provides insights into the ECL mechanistic route operating in bioassays and on the optical effects that focus the ECL emission.