| 1. |
- Abbas, Malik Waseem, et al.
(författare)
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Carbon quantum dot coated Fe3O4 hybrid composites for sensitive electrochemical detection of uric acid
- 2019
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Ingår i: Microchemical journal (Print). - : ELSEVIER SCIENCE BV. - 0026-265X .- 1095-9149. ; 146, s. 517-524
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Tidskriftsartikel (refereegranskat)abstract
- The study explores carbon quantum dots (C-dots) as potential candidates for enhancing the signal sensitivity of an electrochemical sensor devised for biologically important molecule, such as uric acid (UA). The C-dots were evaluated for their electrochemical characteristics in combination with Fe3O4 nanoparticles (Fe3O4 NPs), which were applied as the primary electro-catalytic promoter. The hybrid nanocomposite (C-dots/Fe3O4 HCs) formation was achieved by facilitating the adsorption of C-dots over Fe3O4 NPs using amine-carbonyl interactions. Unlike, one pot method, the proposed strategy enables aggregation-free coverage of Fe3O4 NPs with highly conductive layer of C-dots that can act as conduction centres to support ultra-fast electron transfer kinetics to satisfy the need of high signal sensitivity. The hybrid composite demonstrated remarkable signal improvement when tested against the electrochemical oxidation of UA. The heighten current response and lower over-potential values enabled development of a DC-amperometric (DC-AMP) sensor for UA with a linear working range of 0.01 to 0.145 mu M and signal sensitivity measurable up to 6.0 x 10(-9) M. The said improvement was manifested as a synergetic outcome of active redox couple (Fe (III/II)), larger surface area of Fe3O4 NPs engulfed with a layer of highly conductive C-dots acting as efficient charge sensitisers.
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| 2. |
- Angelin, Eva Mariasole, et al.
(författare)
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The multi-analytical in situ analysis of cadmium-based pigments in plastics
- 2020
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Ingår i: Microchemical Journal. - : Elsevier BV. - 0026-265X. ; 157
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Tidskriftsartikel (refereegranskat)abstract
- © 2020 Elsevier B.V. Colorants are present in trace concentration in objects made of plastic and their identification is a methodological and analytical challenge. In conservation, the identification of colorants may allow a better understanding of colorant degradation (such as color change and fading) and provide information about the historical development, production and processing of plastics. Although micro-destructive analytical protocols are well established for the analysis of colorants, in cultural heritage, where in situ methodologies are preferred and, in some cases, mandatory, new approaches are greatly needed. In this work, an in situ multi-analytical approach is used to specifically study inorganic cadmium-based pigments that were commonly used for coloring plastics during the 20th c. First introduced as vivid artists’ pigments, cadmium-based additives were used for coloring plastics because of their exceptional performance properties. Eighteen colored polymethyl methacrylate (PMMA) samples, produced in the second half of the 20th c. by the company Plásticos do Sado (Portugal), were studied with a combination of optical microscopy, colorimetry, UV–Vis-NIR diffuse reflectance, laser-induced photoluminescence, vibrational (µ-Raman) and elemental (µ-EDXRF) spectroscopies. On the basis of complementary data, the chemical composition of most of the coloring agents employed in the acrylic samples were identified without any micro-sampling.
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| 3. |
- Artesani, A., et al.
(författare)
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Monitoring metal ion leaching in oil-ZnO paint systems with a paramagnetic probe
- 2019
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Ingår i: Microchemical Journal. - : Elsevier BV. - 0026-265X. ; 151
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Tidskriftsartikel (refereegranskat)abstract
- Zinc oxide (ZnO), used as a pigment since the 19th C., is highly reactive when mixed with drying oils. Indeed, the combination of metal-based pigments and drying oils may react to form metal complexes in paint, which may lead to the aggregation of metal carboxylates or soaps. Whereas the mechanism and chemistry behind metal soap formation has been studied in depth, little research has focused on the changes that affect the inorganic pigment particles. In this work, we concentrate on the first phase of these reactions and monitor the evolution of an oil-ZnO paint system through Electron Paramagnetic Resonance (EPR) spectroscopy. By employing CuII as a paramagnetic probe, the progression of metal ion leaching from ZnO is followed through the switching of CuII from a silent tetrahedral coordination in ZnO bulk to an EPR active pseudo-octahedral coordination. Complementarily, the effective concentration of dissolved or extracted Zn and Cu is quantified through Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). The experiment probes the spontaneous metal ion release in oil-based paint films and demonstrates that the kinetics of this phenomenon proceeds with a very steep increase in the first hours after mixing. This is followed by the saturation of the grow rate after a few days that we ascribe to the passivation of the ZnO pigment surface by carboxylate groups, which hinders the further leaching of metal ions, leading to a steady-state before the complete hardening or oxidation of the paint film. © 2019
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| 4. |
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| 5. |
- Cano-Aguilera, I., et al.
(författare)
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Use of hydride generation-atomic absorption spectrometry to determine the effects of hard ions, iron salts and humic substances on arsenic sorption to sorghum biomass
- 2005
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Ingår i: Microchemical Journal. - : Elsevier BV. - 0026-265X. ; 81:1, s. 57-60
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Tidskriftsartikel (refereegranskat)abstract
- At present, there is a great interest in studying new sorbent materials for the removal of arsenic from aqueous solutions because of its high toxicity and adverse effects on human health. In previous research, sorghum biomass was found to be an efficient and economic sorbent for the removal of arsenic from aqueous solutions. In this investigation, the effects of CaCl2, MgCl 2, FeSO4, MgSO4, Fe(NO3) 3, and humic substances (peat moss, humin and humic acids) on arsenic binding to sorghum biomass were evaluated. Among these compounds, only iron salts were found to positively increase the sorption of arsenic to sorghum biomass. In addition, the sorption equilibrium was reached faster when the reaction mixture contained iron salts. However, an overall reduction of 21% of arsenic sorption to sorghum biomass was observed in the presence of MgSO 4. This interference may be due to the presence of sulfate ions, instead of the hard cations, that could be in competition with As for the same interaction sites or ligands. Peat moss, humins and humic acid, extracted from sphagnum peat moss, significantly decreased the arsenic sorption to sorghum biomass.
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| 6. |
- Dominguez, Marina A., et al.
(författare)
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Capillary electrophoresis method for the simultaneous determination of carbohydrates and proline in honey samples
- 2016
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Ingår i: Microchemical journal (Print). - : Elsevier. - 0026-265X .- 1095-9149. ; 129, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- A capillary electrophoresis method with indirect UV detection for the simultaneous determination of three carbohydrates (fructose, glucose and sucrose) and the amino acid proline in honey samples was developed. This method included the use of a background electrolyte consisting of 10 mM sodium benzoate and 1.5 mM cetyltrimethylammonium bromide, pH 12.4. Under optimal capillary electrophoresis conditions, the separation of the investigated substances was achieved in less than 5 min and single dilution of each sample was employed. The detection limits for fructose, glucose and sucrose were 0.58 g L-1, 0.67 g L-1 and 0.12 g L-1 respectively, and 0.72 mg L-1 for proline. Precision measurements calculated in terms of %RSD in the range of 0.92 to 5.43%, were obtained. The proposed method was applied to honey samples from Argentina and Sweden and enables the determination of the three carbohydrates and the amino acid proline. The results show that the proposed method is simple, requires short analysis times, low consumption of reagents and sample, minimum waste and that there is no need to perform any sample pre-treatment. This method is a good alternative to carry out the quality control of honey samples. Finally, it is a promising methodology for achieving green chemistry goals.
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| 7. |
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| 8. |
- Haque, Nazmul, et al.
(författare)
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Iron-modified light expanded clay aggregates for the removal of arsenic(V) from groundwater
- 2008
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Ingår i: Microchemical Journal. - : Elsevier BV. - 0026-265X. ; 88:1, s. 7-13
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Tidskriftsartikel (refereegranskat)abstract
- Iron modified materials have been proposed as a filter medium to remove arsenic compounds from groundwater. This research investigated the removal of arsenate, As(V) from aqueous solutions by iron-coated light expanded clay aggregates (Fe-LECA). Arsenic is effectively adsorbed by Fe-LECA in the optimum pH range 6-7 by using a 10 mg mL(-1) adsorbent dose. Kinetics experiments were performed to investigate the adsorption mechanisms. Electrostatic attraction and surface complexation were proposed to be the major arsenic removal mechanisms. The experimental data fitted the pseudo-first-order equation of Lagergren. For an arsenic concentration of 1 mg L-1, the rate constant (k(1)) of pseudo-first-order was 0.098 min(-1), representing a rapid adsorption in order to reach equilibrium early. Equilibrium sorption isotherms were constructed from batch sorption experiments and the data was best described by the Langmuir isotherm model. Large scale column experiments were conducted under different bed depths, flow rates, coating duration and initial iron salts concentration to determine the optimal arsenic removal efficiency by Fc-LECA column. Volumetric design as well as higher hydraulic detention time was proposed to optimize the efficiency of the column to remove arsenic. In addition, concentrated iron salts and longer coating duration were also found to be crucial parameters for arsenic removal. The maximum arsenic accumulation was 3.31 mg of As g(-1) of Fe-LECA when the column was operated at a flow rate of 10 mL min(-1) and the LECA was coated with 0.1 M FeCl3 suspension for a 24 h coating duration. (C) 2007 Elsevier B.V. All rights reserved.
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| 9. |
- Juranović Cindrić, Iva, 1970-, et al.
(författare)
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Elemental characterisation of the medical herbs Salvia officinalis L. and Teucrium montanum L. grown in Croatia
- 2013
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Ingår i: Microchemical journal (Print). - : Elsevier. - 0026-265X .- 1095-9149. ; 107, s. 185-189
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Tidskriftsartikel (refereegranskat)abstract
- In the presented study samples of sage (Salvia officinalis L) and mountain germander (Teucrium montanum L) as well as infusions prepared from them were investigated for their mineral composition ranging from trace to major elements. Element concentrations in the medical herbs and their infusions were determined by ICP-AES. The following elements were studied: Al, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr, and Zn. Blossoms and leaves of the herb samples were digested in a microwave oven in order to determine the total content of the elements of interest. Infusions were prepared using distilled water of different temperature and applying various decoction times. The extraction yields for all elements present in the infusions were calculated. The essential elements Al, Cu, Fe, Mn, Ni, and Zn are present in the whole overground herb and infusions at concentration levels of mu g/L, whereas Ca, K, Mg, and Na in mg/L. The toxic elements Cd and Pb were found only in the whole overground herb at very low concentrations, but not in the final infusions. High amounts of K, Mg, and Na in the resulting infusions justify the use of this herb as nutritional supplement in addition to the organic compounds.
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| 10. |
- Kučera, Jan, et al.
(författare)
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Tellurium determination by three modes of instrumental neutron activation analysis in aerosol filters and trap solutions for the simulation of a severe nuclear accident
- 2020
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Ingår i: Microchemical Journal. - : Elsevier BV. - 0026-265X. ; 158
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Tidskriftsartikel (refereegranskat)abstract
- Tellurium belongs to the elements not frequently determined by neutron activation analysis (NAA) or other analytical methods. We present results of a new methodological study using three independent modes of instrumental NAA (INAA) using the 123mTe, 131Te and 131I radionuclides. We compare the results obtained in terms of accuracy, precision and limits of detection (LOD). We utilized the INAA procedures tested for the tellurium determination in aerosol filters and trap solutions in a model experiment aimed at reducing the knowledge gap concerning the behaviour of 132Te, a radiologically significant fission product, which constitutes a considerable health risk towards the public in case of its release in a severe nuclear power plant accident. We found that the nuclear reaction 130Te(n,γ)131Te and gamma-ray spectrometric measurement of 131I, a descendant of 131Te, is the most sensitive way of Te determination by INAA providing as low LOD values as 0.15 µg of Te in the Teflon aerosol filters and 0.22 µg mL-1 in the 0.1 M NaOH trap solutions. The three independent INAA modes allowed employing the self-verification principle of INAA for increasing the trustworthiness of our results. Finally, we also point to the indispensable role of the non-destructive feature of INAA for assay of samples, such as Teflon aerosol filters, that are difficult to be analysed by other analytical methods requiring complete sample destruction without analyte losses.
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