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Abstract  

The molar heat capacity and the standard (p 0 = 0.1 MPa) molar enthalpies of formation of the crystalline of bis(glycinate)lead(II), Pb(gly)2; bis(dl-alaninate)lead(II), Pb(dl-ala)2; bis(dl-valinate)lead(II), Pb(dl-val)2; bis(dl-valinate)cadmium(II), Cd(dl-val)2 and bis(dl-valinate)zinc(II), Zn(dl-val)2, were determined, at T = 298.15 K, by differential scanning calorimetry, and high precision solution-reaction calorimetry, respectively. The standard molar enthalpies of formation of the complexes in the gaseous state, the mean molar metal–ligand dissociation enthalpies, M(II)–amino acid,
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\langle D_{\text{m}} \rangle$$ \end{document}
(M–L), were derived and compared with analogous copper(II)–ligand and nickel(II)–ligand.θθ
M(II)–amino acid
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\Updelta_{\text{f}} H_{\text{m}}^{\text{o}}$$ \end{document}
(cr)/kJ mol−1
Bis(glycinate)lead(II), Pb(gly)2 −998.9 ± 1.9
Bis(dl-alaninate)lead(II), Pb(ala)2 −1048.7 ± 1.8
Bis(dl-valinate)lead(II), Pb(val)2 −1166.3 ± 2.5
Bis(dl-valinate)cadmium(II), Cd(val)2 −1243.7 ± 2.7
Bis(dl-valinate)zinc(II), Zn(val)2 −1306.1 ± 2.3
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Abstract  

The vapour pressures of six para-substituted benzoic acids were measured using the Knudsen effusion method within the pressure range (0.1–1 Pa) in the following temperature intervals: 4-hydroxybenzoic acid (365.09–387.28) K; 4-cyanobenzoic acid (355.14–373.28) K; 4-(methylamino)benzoic acid (359.12–381.29) K; 4-(dimethylamino)benzoic acid (369.29–391.01) K; 4-(acetylamino)benzoic acid (423.10–443.12) K; 4-acetoxybenzoic acid (351.28–373.27) K. From the temperature dependence of the vapour pressure, the standard molar enthalpy, entropy and Gibbs energy of sublimation, at the temperature 298.15 K, were derived for each of the studied compounds using estimated values of the heat capacity differences between the gaseous and the crystalline phases. Equations for estimating the vapour pressure of para substituted benzoic acids at the temperature of 298.15 K are proposed.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Luís dos Santos, Márcio Bacchi, Elisabete De Nadai Fernandes, and Simone da Silva Cofani dos Santos

Abstract  

As a non-destructive and multi-element technique, with high-level metrological properties, instrumental neutron activation analysis (INAA) has an important role to determine chemical elements in food. However, its use may be limited when looking for mass fractions near the detection limits. The Compton scattering of higher energy gamma-rays raised the spectrum baseline thus impairing the determination of several elements. Therefore, the gamma-ray spectrometry with Compton suppression becomes an alternative for improving the performance of INAA, since it can reduce the uncertainty of measurements and the detection limits by increasing the proportion between photopeak area and baseline. Here the performance of a Compton suppression system set by Ortec, with 50% relative efficiency and 2.04 keV resolution (FWHM) for the 1,332 keV photopeak, was evaluated for food analysis. Samples of beans, chickpeas, lentils, peas, and rice were irradiated with neutrons and measured in the suppression system. Detection limits calculated from suppressed and unsuppressed spectra were compared. The suppression factor achieved by the system for 137Cs was 5.88 ± 0.11 (n = 20) in the plateau region (358 to 382 keV), which was stable along a 20 week period and similar to the data provided in literature for other systems. Amongst fifteen elements determined, the detection limits for Br, Co, La, Na, Sc, and Se were not improved by the use of Compton suppression. On the other hand, the variable improvement obtained for As, Ca, Cd, Cr, Fe, Hg, K, Rb, and Zn corroborated the idea that the performance of the Compton suppressor must be individually assessed for each type of sample.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Luís dos Santos, Elisabete De Nadai Fernandes, Simone da Silva Cofani dos Santos, Márcio Bacchi, Gabriel Sarriés, and Fernando Júnior

Abstract  

Brazil started to export dairy products in the early 2000s and since then has slowly consolidated its position in the world dairy market. To ensure the position in the international market by improving the quality of milk produced in the country, the government created a national program and a network of laboratories for milk quality. The Normative Instruction 51 (Instrução Normativa 51IN51) was introduced within the national program establishing parameters for milk quality and safety. In spite of not being included in the IN51, chemical elements are under thorough discussion as quality parameters for their nutritional and toxicological relevance. This work aimed at evaluating the quality of milk from one of the major dairy regions in Brazil, located in the state of Rio Grande do Sul, by the determination of chemical elements, comparing the results with those previously obtained for milk samples from the main dairy region of the country, in the state of Minas Gerais. Samples were collected from cooling tanks in nineteen dairy farms. After freeze drying, chemical elements were determined by instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS). For ten out of sixteen chemical elements determined, there were significant differences between samples from both producing regions (p < 0.01).

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Luís dos Santos, Elisabete De Nadai Fernandes, Márcio Bacchi, Gabriel Sarriés, Lucimara Blumer, and Fernando Júnior

Abstract  

Aiming at international competitiveness of the Brazilian dairy sector, new governmental policies were released to improve quality and safety of bovine milk. In this context, it is important to quantify essential and toxic chemical elements. Here, the composition of milk samples taken at 32 dairy farms in Minas Gerais State was assessed by instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS), besides the evaluation of usual quality parameters. Significant differences were found for Ba, K, Na and fat content amongst dairy farms with diverse quality levels established on basis of somatic cell and total bacterial count.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Luís dos Santos, Elisabete De Nadai Fernandes, Márcio Bacchi, Gabriel Sarriés, Lucimara Blumer, and Fernando Barbosa

Abstract  

The bovine dairy cattle demand diets of high nutritional value being essential to know chemical composition of feed supplied to cows to achieve high levels of quality, safety and productivity of milk. Different roughages and concentrates from Minas Gerais and Rio Grande do Sul states, Brazil, were analyzed by instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS). Concentrate and roughage samples were differentiated by mass fractions of As, Ba, Mg, P, Rb and Sr. Samples of concentrate from both origins were differentiated by mass fractions of As, Cd, Co, Cr, Cs, Ni and Rb.

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Journal of Thermal Analysis and Calorimetry
Authors: Joana Cabral, Ricardo Monteiro, Marisa Rocha, Luís Santos, William Acree, and Maria Ribeiro da Silva

Abstract  

The standard ( = 0.1 MPa) energies of combustion in oxygen, at T = 298.15 K, for the solid compounds 2-methylpyridine-N-oxide (2-MePyNO), 3-methylpyridine-N-oxide (3-MePyNO) and 3,5-dimethylpyridine-N-oxide (3,5-DMePyNO) were measured by static-bomb calorimetry, from which the respective standard molar enthalpies of formation in the condensed phase were derived. The standard molar enthalpies of sublimation, at the same temperature, were measured by Calvet microcalorimetry. From the standard molar enthalpy of formation in gaseous phase, the molar dissociation enthalpies of the N–O bonds were derived, and compared with values of the dissociation enthalpies of other N–O bonds available for other pyridine-N-oxide derivatives.

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Dissemination of pathogenic multiresistant bacteria is of public health concern. Reliable data can be difficult to obtain, especially in developing countries. This work aimed to characterize the skin and oropharyngeal microbiota, as well as their antimicrobial resistance profiles, of East-Timor populations to identify potentially pathogenic Gram-positive cocci. In order to assess the prevalence of pathogenic bacteria in East-Timor, the oropharyngeal and skin microbiota of 74 individuals was characterized. Gram-positive cocci were evaluated and their antimicrobial resistance profiles were determined. A total of 228 oropharyngeal and 278 skin samples were obtained. The population consisted of 36.5% of asymptomatic carriers of Gram-positive cocci. Kocuria rosea (n = 7, 19.4%), Staphylococcus spp. (n = 6, 16.7%), and Micrococcus luteus (n = 6, 16.7%) were isolated, among others. Antimicrobial resistance levels ranged between 0% and 36.1%, and a multiresistance profile was observed in one third of the isolates. Gram-positive cocci colonization was associated with age group. Prevalence of multiresistant isolates was higher in males who were sampled at the refugee camp. Results show that the prevalence of antimicrobial resistance on East Timor may be underestimated. This study represents the first step toward the full characterization of potential pathogenic Gram-positive cocci present in the populations from East Timor.

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