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Some endocrine disruptors, such as active substances and metabolites of some medicines or preservatives of personal-care products are known to be concentrating in the environment due to the inefficiency of wastewater treatment plants to... more
Some endocrine disruptors, such as active substances and metabolites of some medicines or preservatives of personal-care products are known to be concentrating in the environment due to the inefficiency of wastewater treatment plants to remove these residues. There are cases in which photodegradation with UV-light o rf rom sunlight radiation can be successfully applied. Nevertheless, available technologies are, in many cases, not feasible due to the energy requirements or duration of relevant residues reduction. Some catalysts, mainly semiconductor nanomaterials, have been develope dt o improve the efficiency of such processes1. The new technologies are first assessed in the laboratory for some pollutants or photodegradation markers and, if proved efficient, applied to more complex systems. This work presents a strategy to develop reliable detailed models of the determination of the efficiency gain of the catalytic photodegradation of methylene blue. Methylene blue was chosen since ...
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Seawater pH values are of the highest relevance in marine chemistry studies, not only through being acidity indicators but also due to the control provided by H+(aq) over the various simultaneous equilibria occurring in seawater. Although... more
Seawater pH values are of the highest relevance in marine chemistry studies, not only through being acidity indicators but also due to the control provided by H+(aq) over the various simultaneous equilibria occurring in seawater. Although the concept of p H = − l g a H + = − lg ( m H + γ H + / m 0 ) $\mathrm{p}\mathrm{H}=-\mathrm{l}\mathrm{g}{\mathit{a}}_{{\mathrm{H}}^{+}}=-\mathrm{lg}\left({\mathit{m}}_{{\mathrm{H}}^{+}}{\mathit{\gamma }}_{{\mathrm{H}}^{+}}/{\mathit{m}}^{0}\right)$ , where m H + ${m}_{{\text{H}}^{+}}$ is the relative (molality basis) activity, γ H + ${\gamma }_{{\text{H}}^{+}}$ is the molal activity coefficient of the hydrogen ion H+ at molality m H + ${m}_{{\text{H}}^{+}}$ , and m 0 is the standard molality, was introduced in 1910 and reaffirmed on successive occasions by relevant bodies, different conceptual definitions and alternative measurement procedures have been adopted and are in use by some, namely among oceanographers, often leading to confusion. This le...
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Recommendations are given concerning the terminology of methods used in electroanalytical chemistry. Fundamental terms in electrochemistry are reproduced from previous PAC Recommendations, and new and updated material is added for terms... more
Recommendations are given concerning the terminology of methods used in electroanalytical chemistry. Fundamental terms in electrochemistry are reproduced from previous PAC Recommendations, and new and updated material is added for terms in electroanalytical chemistry, classification of electrode systems, and electroanalytical techniques.
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ABSTRACT Platinized platinum based hydrogen gas electrodes, Pt(Pt)|H2(g)|H+(aq), and silver-silver chloride electrodes, Ag|AgCl|Cl− (aq), make up the Harned cell, without transfer, working in the potentiometric mode at Cl− concentrations... more
ABSTRACT Platinized platinum based hydrogen gas electrodes, Pt(Pt)|H2(g)|H+(aq), and silver-silver chloride electrodes, Ag|AgCl|Cl− (aq), make up the Harned cell, without transfer, working in the potentiometric mode at Cl− concentrations and ionic strengths, I, below 0.1 mol kg−1, for assigning primary pH values to reference pH buffer solutions. This work reports on experiments performed at higher I and Cl− solutions up to 0.7 mol kg−1, aiming at addressing seawater conditions with results of equally high quality. In the course of measurements, the occasional occurrence of highly unstable potentials denoted electrode malfunction; Pt metal surfaces observed by SEM/EDS and XRD exhibit strong Ag and Cl peaks corresponding to the presence of AgCl crystals deposited at both surfaces.
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ABSTRACT In this work, particulate matter was collected using an active sampling system consisting of a PM10 (<10 μm) inlet coupled to a multifold device containing six channels, connected to a vacuum pump. Each channel was... more
ABSTRACT In this work, particulate matter was collected using an active sampling system consisting of a PM10 (<10 μm) inlet coupled to a multifold device containing six channels, connected to a vacuum pump. Each channel was equipped with a filter holder fitted with adequately chosen filters. The system was fixed on a metallic structure, which was placed on the roof of the laboratory building, at the Faculty of Sciences, in Lisbon. Sampling took place under flow-controlled conditions. Aerosols were extracted from the filters with water, in defined conditions, and the water-soluble fraction was quantified by ion chromatography (IC) for the determination of inorganic anions (Cl(-), NO3 (-) and SO4 (2-)). Equivalent sampling through the various channels was validated. Validation was based on the metrological compatibility of the content results for the various filters. Ion masses are metrologically equivalent when their absolute difference is smaller than the respective expanded uncertainty. When this condition is verified, the studied multifold device produces equivalent samples.
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Research Interests: Engineering, Graduate Education, Adult Continuing and Professional Education, Accreditation, Employment, and 12 moreMedicine, Curriculum, Biological Sciences, Medical Laboratory, Analytic Chemistry, Graduate medical education, Professional Military Education, Laboratories, CHEMICAL SCIENCES, Internationality, Analytical and Bioanalytical Chemistry, and Professional Competence
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Research Interests: Chemistry, Chromatography, Food Chemistry, Medicine, Multidisciplinary, and 15 moreValidation, HPLC, Uncertainty Estimation, Tomato, High Performance Liquid Chromatography, Lycopene, Regional Variation, Carotenoid, Lutein, Repeatability, Food chem, Method Validation, Compositional Data, Lycopersicon esculentum, and Measurement Uncertainty
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Research Interests: Chemistry, Analytical Chemistry, Mass Spectrometry, Atomic Spectroscopy, Accreditation and Quality Assurance, and 10 moreQuantitative analysis, Uncertainty Estimation, Uncertainty analysis, Tool Development, Uncertainty propagation, Atomic Absorption, Quantitative Analysis, Measurement Uncertainty, Propagation of uncertainty, and Springer Ebooks
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The definition of a “primary method of measurement ” has permitted a full consideration of the definition of primary standards for pH, determined by a primary method (cell without transference, Harned cell), of the definition of secondary... more
The definition of a “primary method of measurement ” has permitted a full consideration of the definition of primary standards for pH, determined by a primary method (cell without transference, Harned cell), of the definition of secondary standards by secondary methods, and of the question whether pH, as a conventional quantity, can be incorporated within the internationally accepted system of measurement, the International System of Units (SI, Système International d’ Unités). This approach has enabled resolution of the previous compromise IUPAC 1985 Recommendations [Pure Appl. Chem. 57, 531 (1985)]. Furthermore, incorporation of the uncertainties for the primary method, and for all subsequent measurements, permits the uncertainties for all procedures to be linked to the primary standards by an unbroken chain of comparisons. Thus, a rational choice can be made by the analyst of the appropriate procedure to achieve the target uncertainty of sample pH. Accordingly, this document expl...
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An explanation of the origin and interpretation of the suspension effect (SE) is presented in accordance with "pH Measurement: IUPAC Recommendations 2002" [Pure Appl. Chem.74, 2169 (2002)]. It is based on an analysis of detailed... more
An explanation of the origin and interpretation of the suspension effect (SE) is presented in accordance with "pH Measurement: IUPAC Recommendations 2002" [Pure Appl. Chem.74, 2169 (2002)]. It is based on an analysis of detailed schemes of suspension potentiometric cells and confirmed with experimental results. Historically, the term "suspension effect" evolved during attempts to determine electrochemically the thermodynamically defined activity of H+ (aq) in suspensions. The experimental SE arises also in determining other pIon values, analogous to pH values.The SE relates to the observation that for the potential generated when a pair of electrodes (e.g., reference electrode, RE, and glass electrode) is placed in a suspension, the measured cell voltage is different from that measured when they are both placed in the separate equilibrium solution (eqs). The SE is defined here as the sum of: (1) the difference between the mixed potential of the indicator electrod...
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ABSTRACT Atmospheric aerosol sampling has been performed in parallel with both high and low air flows. A comparison of the results requires proper statistical design and analysis. The presence of several outliers and the increase of... more
ABSTRACT Atmospheric aerosol sampling has been performed in parallel with both high and low air flows. A comparison of the results requires proper statistical design and analysis. The presence of several outliers and the increase of residuals with increasing concentration have led to the recommendation of handling the data with non-parametric methods rather than parametric statistical analysis. Conversion equations were obtained for each of the ionic species examined for prediction of low air flow sampling from long-term observations with high air flow sampling.
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The knowledge of the mass of particulate matter in air, its chemical composition and emission sources is of relevance for taking decisions concerning air quality management in urban areas. The interpretation of these data is a function of... more
The knowledge of the mass of particulate matter in air, its chemical composition and emission sources is of relevance for taking decisions concerning air quality management in urban areas. The interpretation of these data is a function of the quality of the measurement results expressed by their uncertainties. This study aimed at developing models of the performance of the determination of anions in the water-soluble fraction of atmospheric aerosols, capable of determining, separately, the contribution of aerosols sampling, extraction of water-soluble fraction of atmospheric aerosols and quantification, by ion chromatography, of anions in the extract. The sampling procedure was assessed from the dispersion of results of duplicate parallel sampling after subtracting the analytical component of this dispersion. These models are used to evaluate the adequacy of the measurement procedure for the determination of urban aerosol composition and to support strategies for reducing measuremen...
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Potentiometric evaluation of ionic concentrations in physiological media has been reported to be significantly affected by the albumin containing matrix. Previous studies have attempted to clarify the origin of different patterns of... more
Potentiometric evaluation of ionic concentrations in physiological media has been reported to be significantly affected by the albumin containing matrix. Previous studies have attempted to clarify the origin of different patterns of variation of E versus albumin concentration at a constant 0.01 mol dm-3 KCl, depending on the experimental methodologies. This paper reports on measurements of K+ in albumin (BSA) containing KCl solutions, which have been pursued following different methodologies concerning the sequence of measurements, i.e., starting either from the most concentrated solution (100 g dm-3) (A) or from the most dilute solution (20 g dm-3) (B), and solution preparation, (a) dilution of an initial 100 g dm-3 albumin solution by successive addition of 0.01 mol dm-3 KCl, (b) concentration of an initial 20 g dm-3 albumin solution by addition of solid substance, (c) independent preparation of each albumin solution (20, 40, 60, 80 and 100 g dm-3) or (d) preparation of each albumin solution from direct dilution of a 100 g dm-3 stock solution with 0.01 mol dm-3 KCl. Convenient calculations were made and showed a significant contribution of albumin to the liquid-liquid junction potential. The variation of potential with albumin concentration is smaller for hypertonic than for isotonic bridge solutions, both for the dilution series (A,a and A,d) and for the concentration series (B,c and B,d). When the method for increasing the concentration is performed by addition of a solid substance to an initially diluted albumin (B,b), the slope of the E versus albumin concentration plot is larger for hypertonic than for isotonic reference electrolytes. This latter finding is in agreement with Payne's results when ultrafiltration was used to concentrate a protein solution. These observations are a clear indication that the method of preparation of concentrated protein solutions may significantly affect the results.