The first and second ionization energies of the element 119: absolute hardness and Mulliken electronegativity for the cation 119+ based on an empirical equation involving absolute hardness

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High performance liquid chromatography applied in hormone contaminations detection: A scoping review in ecotoxicology

The present work shows a systematic overview of studies about the methods used to quantify the estrogen 17β-estradiol, estrone, estriol and 17α-ethynylestradiol in surface water through high performance liquid chromatography. The PubMed, Web of Science, and Scopus databases were searched. Articles from the last 10 years have been selected, and only in English language. Literature search strategy involved the keywords “estradiol”, “High Performance Liquid Chromatography”, “HPLC” and “water”. Initially, 955 articles were found. After applying the exclusion criteria (repetition, objective different from scope, lack of information defined as elementary, free availability, among others), it was verified that 17 articles fulfill all the characteristics for the proposed overview. We extracted data on type of HPLC equipment, detectors, wavelength, chromatographic columns, limit of detection, limit of quantification, mobile phase, and time retention. The most commonly used detectors were the tandem mass spectrometric. The limits of detection and quantification were in the unit of measurement of ng?L^?1. With this overview, the importance of high-performance liquid chromatography has been demonstrated to deepen research on estrogen hormone quantification, given the current growth of scientific community concern about the detection of such endocrine disrupters in surface water.     

Impact of electrodialytic parameters on cation migration kinetics and fouling nature of ion-exchange membranes during treatment of solutions with different magnesium/calcium ratios

During electrodialysis (ED) treatment of solutions with different Mg/Ca ratios (R = 0, 1/20, 1/10, 1/5 and 2/5) and in different pH conditions (acid, neutral and basic), foulings on ion-exchange membranes were previously characterized and identified, by the way of X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. A mineral fouling was observed in neutral and basic conditions (for R = 1/5 and 2/5) on the anion-exchange membrane (AEM) concentrate side and in basic conditions on the cation-exchange membrane (CEM) concentrate side as well as on the diluate side for R = 1/5 and 2/5. The objectives of this present work were to link the morphological characterization and identification of membrane fouling to electrodialytic parameters and cation migration kinetics. It appeared that the CEM permselectivity was severely affected in basic conditions for R ≥ 1/5. The consequence of this alteration was the migration of OH⁻ through the CEM, a pH increase in the diluate compartment and different treatment durations. The calcite observed on AEM concentrate side for Mg/Ca ≥ 1/5 would be due first to the particular operating conditions such as the recirculation of the concentrate solution, and also to the supersaturated conditions reached or not at the AEM interface and favourable pH conditions.     

Use of hydrogen peroxide to achieve interference-free stripping voltammetric determination of copper at the bismuth-film electrode

In this work, a new approach is presented to allow interference-free determination of Cu (II) by stripping voltammetry using the bismuth-film electrode. The addition of hydrogen peroxide to the electroanalytical cell has promoted complete resolution between re-dissolution peaks of Bi (III) and Cu (II). The absence of interference could be evaluated by the correlation coefficient (r > 0.99) between Cu (II) concentration and its shifted current peak (at +212 mV) while achieving a slightly fluctuation of the bismuth current peak at −180 mV. Studies were performed aiming towards the optimum conditions for trace determination of Cu (II) using hydrogen peroxide. The methodology was applied to a real sample (sugarcane spirits) and the results were compared to those from graphite furnace atomic absorption spectrometry. The analytical parameters of merit and the results of the analysis indicated that the analytical methodology could be readily used for trace determination of Cu (II).     

Confined electron and shallow donor states in graded GaAs/Al Ga As spherical quantum dots

A theoretical study is performed on the confined electron and shallow donor states properties in graded GaAs/Al_xGa_1-xAs spherical quantum dots. The two lowest energy levels of a confined electron are obtained taking into account the dependence of the electron effective mass on the spatial profile of the Al molar fraction. The ground state of a single Si shallow donor, which may be located at an arbitrary position in the structure, is calculated through a variational approach. Depending on the dot interface width and localization, we find that the energy levels of the electron and donor states for the system under study can be blue or red shifted appreciably in comparison to those calculated within the sharp interface picture. We show that it is necessary to have accurate information concerning the interface of semiconductor dots whose samples are used in the experiments, in order to achieve a better understanding of their optical properties. Received 31 May 1999     

Surface shape resonances of ridges on a thin film

The spectrum of surface shape resonances associated with a finite number of ridges on one interface of an otherwise plane film is calculated. The frequencies are obtained numerically by solving the homogeneous integral equations which describe the electrostatic field in the vicinity of a surface defect. The calculations are performed for a surface with ridges with Gaussian, Lorentzian and sinusoidal profiles. The results show a strong dependence of the localized plasmon frequencies on the surface profile, on the distance between the ridges, and on the thickness of the film. Received 5 April 1999 and Received in final form 6 July 1999     

Cytotoxicity and physico-chemical evaluation of acetylated and pegylated cellulose nanocrystals

The high hydrophilicity of cellulose nanocrystals (CNC) may result in poor dispersion in some matrices and solvents. So in this work, two different methodologies were used to reduce the hydrophilicity of CNC. In the first methodology, CNC were acetylated (CNC-Ac) in a mixture of acetic and hydrochloric acid, and in the second methodology, polyethylene glycol (PEG) was adsorbed onto CNC surface (CNC-PEG) under stirring in aqueous solution. CNC obtained by both methods were characterized by transmission electron microscopy (TEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS), zeta potential, and thermogravimetric analysis (TGA). Images of TEM showed that the intrinsic morphology of cellulose was preserved after both treatments. FTIR confirmed acetylation reaction by the presence of a new band at 1732 cm^?1 (acetate groups) and the consumption of OH groups. XRD showed a reduction in the crystallinity index for both applied methodologies. DLS showed reduced stability in water for CNC-Ac and CNC-PEG. Values of zeta potential changed after acetylation, from ??45 mV (CNC) to ??1 mV (CNC-Ac), and after adsorption of PEG, to ??26.7 mV (CNC-PEG). TGA showed a reduction in the thermal stability after both treatments and a change in the main degradation behavior for CNC-PEG. MTT assays showed that both proposed functionalizations induce cell proliferation, being even more evident for acetylation because, in addition to viability increase with time, it increased with the sample concentration.     

An electrochemical evidence of free radicals formation from flutamide and its reactivity with endo/xenobiotics of pharmacological relevance

This paper reports the feasibility of free radicals formation from flutamide by using cyclic voltammetry. The electrochemical characteristics and the reactivity of the one-electron reduction product from flutamide in mixed media with thiol compounds and the nuclei acid bases are characterized. Results from this paper show the thermodynamic feasibility of free radical formation expressed for both the cathodic peak potential and the second-order rate constant values. The reactivity of the radical towards thiol compounds (glutathione, cysteamine, N-acetylcysteine) and the nuclei acid base, adenine, thymine and uracil were quantitatively assessed through the calculation of the respective interaction rate constants. Based on these results, the following tentative order of reactivity towards the xeno/endobiotics is as follows: cysteamine > uracil > glutathione > adenine > N-acetylcysteine > thymine. The stability of the nitro radical anion electrochemically generated from flutamide showed a linear dependence with pH.