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Glyphosate (N- (phosphonomethyl) glycine) is one of the most widely used herbicides in the world. In the literature, there are several studies describing the interaction between glyphosate and clay minerals. However, there is a lack of data of this interaction in marine environments. In this research, we examined the adsorption of glyphosate onto montmorillonite in the presence of artificial seawater. Mössbauer data showed that the interaction of the phosphonate group of glyphosate with Fe2+ of montmorillonite prevents its oxidation to Fe3+. X-ray diffractograms showed that glyphosate adsorption takes place only onto the montmorillonite surface and not in its interlayers. Infrared spectroscopy data demonstrate that the interaction between glyphosate and montmorillonite could be through the amino group. FT-IR spectra of aqueous solutions of salts of seawater showed that Ca2+ interacts with glyphosate of the phosphonate group, thus causing an increase in its adsorption onto montmorillonite. However, glyphosate dissolved in 0.50 mol L-1 NaCl and 0.034 mol L-1MgCl2 solutions showed the lowest adsorption onto montmorillonite. In addition, the adsorption of glyphosate onto montmorillonite decreased when the NaCl concentration increased. The results fitted the Sips isotherm model, probably because the Ca2+ interacts with glyphosate, making the adsorption process more homogeneous. Thus, n values for Freundlich and Sips isotherm models decreased with an increase in ionic strength. Glyphosate and ions of artificial seawater increased the pHpzc of montmorillonite.

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Probably one of the most important roles played by minerals in the origin of life on Earth was to pre-concentrate biomolecules from the prebiotic seas. There are other ways to pre concentrate biomolecules such as wetting/drying cycles and freezing/sublimation. However, adsorption is most important. If the pre-concentration did not occur-because of degradation of the minerals-other roles played by them such as protection against degradation, formation of polymers, or even as primitive cell walls would be seriously compromised. We studied the interaction of two artificial seawaters with kaolinite, bentonite, montmorillonite, goethite, ferrihydrite and quartz. One seawater has a major cation and anion composition similar to that of the oceans of the Earth 4.0 billion years ago (ASW 4.0 Ga). In the other, the major cations and anions are an average of the compositions of the seawaters of today (ASWT). When ASWT, which is rich in Na+ and Cl-, interacted with bentonite and montmorrilonite structural collapse occurred on the 001 plane. However, ASW 4.0 Ga, which is rich in Mg2+ and SO42-, did not induce this behavior. When ASW 4.0 Ga was reacted with the minerals for 24 h at room temperature and 80 °C, the release of Si and Al to the fluid was below 1 % of the amount in the minerals-meaning that dissolution of the minerals did not occur. In general, minerals adsorbed Mg2+ and K+ from the ASW 4.0 Ga and these cations could be used for the formation of polymers. Also, when the minerals were mixed with ASW 4.0 Ga at 80 °C and ASWT at room temperature or 80 °C it caused the precipitation of CaSO4∙2H2O and halite, respectively. Finally, further experiments (adsorption, formation of polymers, protection of molecules against degradation, primitive cell wall formation) performed under the conditions described in this paper will probably be more representative of what happened on the prebiotic Earth.

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Modelo de estudo: Estudo transversal e qualitativo. Objetivos: Este trabalho investiga as vivências e identifica as percepções dos discentes do internato do nono período de medicina de uma universidade pública, sobre dependência química pelo crack. Metodologia: Estudo transversal de abordagem qualitativa, cujo instrumento da pesquisa foi uma entrevista individual, utilizando-se um roteiro semiestruturado, que permite amplo discurso dos discentes. As falas das gravações foram transcritas e depois realizada a análise do conteúdo segundo Bardin. Resultados: Foram identificadas categorias referentes ao sentimento da vivência, à percepção do discente sobre a dependência do crack e seu aprendizado sobre o tema, aos comprometimentos físicos, aos outros prejuízos causados e a como a sociedade deve lidar diante da dependência química pelo crack. Os sentimentos de compaixão e de preservação estão presentes em suas vivências. Os discentes relacionam as questões econômicas, profissionais e familiares como fontes das graves consequências do crack. Valorizam os prejuízos sociais e existenciais, a autodestruição, a violência e o emagrecimento que o crack causa aos usuários, além da codependência. É grande a preocupação dos discentes com a prevenção, educação, informação, eliminação do preconceito e cobranças de ações governamentais para combate ao crack. Conclusão: Os discentes do internato consideram a dependência química pelo crack como problema social e doença.Definem como insuficiente o aprendizado sobre a dependência química pelo crack durante o curso. Suas vivências e percepções geram impactos positivos, pois apontam para futuros egressos melhor preparados, que deverão acolher o dependente e sua família de forma mais ampla, humana e eficaz.

Study design: Cross-sectional and qualitative study. Objectives: This study investigates experiences and identifies the perceptions of ninth-term intern medical students of a public university on the crack addiction issue. Methods: A qualitative-approach and cross-sectional study which had as the research tool a semi-structured, individual interview allowing broad speech of students. Recording reports were transcribed and content analysis carried out according to Bardin. Results: categories were identified concerning the feeling of experience, the students’ perception on crack addiction and their learning on the subject, physical impairments and additional damages, besides how society should deal with the addiction on crack. The feelings of compassion and preservation are present in their experiences. Students point out economic, professional and family issues as the sources of serious crack addiction consequences. They also take into account the social and existential damages, the self-destruction, violence and weight loss caused on crack users, as well as the codependency. There is a great concernon the part of students related to prevention, education, information, elimination of prejudice, as well as demands of government efforts to combat crack. Conclusion: The intern medical students consider crack addiction both a social problem and a disease; define learning about addiction by crack insufficient throughout the course. Their experiences and perceptions generate positive impacts since they prospect better prepared graduates who shall receive the one addicted and his family in a broader, more effective and humane way.

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Minerals could have played an important role in concentration, protection, and polymerization of biomolecules. Although iron is the fourth most abundant element in Earth's crust, there are few works in the literature that describe the use of iron oxide-hydroxide in prebiotic chemistry experiments. In the present work, the interaction of adenine, thymine, and uracil with ferrihydrite was studied under conditions that resemble those of prebiotic Earth. At acidic pH, anions in artificial seawater decreased the pH at the point of zero charge (pHpzc) of ferrihydrite; and at basic pH, cations increased the pHpzc. The adsorption of nucleic acid bases onto ferrihydrite followed the order adenine >> uracil > thymine. Adenine adsorption peaked at neutral pH; however, for thymine and uracil, adsorption increased with increasing pH. Electrostatic interactions did not appear to play an important role on the adsorption of nucleic acid bases onto ferrihydrite. Adenine adsorption onto ferrihydrite was higher in distilled water compared to artificial seawater. After ferrihydrite was mixed with artificial seawaters or nucleic acid bases, X-ray diffractograms and Fourier transform infrared spectra did not show any change. Surface-enhanced Raman spectroscopy showed that the interaction of adenine with ferrihydrite was not pH-dependent. In contrast, the interactions of thymine and uracil with ferrihydrite were pH-dependent such that, at basic pH, thymine and uracil lay flat on the surface of ferrihydrite, and at acidic pH, thymine and uracil were perpendicular to the surface. Ferrihydrite adsorbed much more adenine than thymine; thus adenine would have been better protected against degradation by hydrolysis or UV radiation on prebiotic Earth.

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The interactions of adenine and thymine with and adsorption on zeolites were studied using different techniques. There were two main findings. First, as shown by X-ray diffractometry, thymine increased the decomposition of the zeolites (Y, ZSM-5) while adenine prevented it. Second, zeolite Y adsorbed almost the same amount of adenine and thymine, thus both nucleic acid bases could be protected from hydrolysis and UV radiation and could be available for molecular evolution. The X-ray diffractometry and SEM showed that artificial seawater almost dissolved zeolite A. The adsorption of adenine on ZSM-5 zeolite was higher than that of thymine (Student-Newman-Keuls test-SNK p<0.05). Adenine was also more greatly adsorbed on ZSM-5 zeolite, when compared to other zeolites (SNK p<0.05). However the adsorption of thymine on different zeolites was not statistically different (SNK p>0.05). The adsorption of adenine and thymine on zeolites did not depend on pore size or Si/Al ratio and it was not explained only by electrostatic forces; rather van der Waals interactions should also be considered.

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In the present work the interactions of nucleic acid bases with and adsorption on clays were studied at two pHs (2.00, 7.00) using different techniques. As shown by Mössbauer and EPR spectroscopies and X-ray diffractometry, the most important finding of this work is that nucleic acid bases penetrate into the interlayer of the clays and oxidize Fe(2+) to Fe(3+), thus, this interaction cannot be regarded as a simple physical adsorption. For the two pHs the order of the adsorption of nucleic acid bases on the clays was: adenine ≈ cytosine > thymine > uracil. The adsorption of adenine and cytosine on clays increased with decreasing of the pH. For unaltered montmorillonite this result could be explained by electrostatic forces between adenine/cytosine positively charged and clay negatively charged. However for montmorillonite modified with Na(2)S, probably van der Waals forces also play an important role since both adenine/cytosine and clay were positively charged. FT-IR spectra showed that the interaction between nucleic acid bases and clays was through NH(+) or NH (2) (+) groups. X-ray diffractograms showed that nucleic acid bases adsorbed on clays were distributed into the interlayer surface, edge sites and external surface functional groups (aluminol, silanol) EPR spectra showed that the intensity of the line g ≈ 2 increased probably because the oxidation of Fe(2+) to Fe(3+) by nucleic acid bases and intensity of the line g = 4.1 increased due to the interaction of Fe(3+) with nucleic acid bases. Mössbauer spectra showed a large decreased on the Fe(2+) doublet area of the clays due to the reaction of nucleic acid bases with Fe(2+).

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The present study examined the adsorption of cysteine, thiourea and thiocyanate on bentonite and montmorillonite at two different pHs (3.00, 8.00). The conditions used here are closer to those of prebiotic earth. As shown by FT-IR, Mössbauer and EPR spectroscopy and X-ray diffractometry, the most important finding of this work is that cysteine and thiourea penetrate into the interlayer of the clays and reduce Fe(3+) to Fe(2+), and as consequence, cystine and c,c'-dithiodiformamidinium ion are formed. This mechanism resembles that which occurs with aconitase. This is a very important result for prebiotic chemistry; we should think about clays not just sink of molecules, but as primitive vessels of production of biomolecules. At pH 8.00, an increasing expansion was observed in the following order for both minerals: thiourea > thiocyanate > cysteine. At pH 3.00, the same order was not observed and thiourea had an opposite behavior, being the compound producing the lowest expansion. Mössbauer spectroscopy showed that at pH 8.00, the proportion of Fe(2+) ions in bentonite increased, doubling for thiourea, or more than doubling for cysteine, in both clays. However, at pH 3.00, cysteine and thiourea did not change significantly the relative amount of Fe(2+) and Fe(3+) ions, when compared to clays without adsorption. For thiocyanate, the amount of Fe(2+) produced was independent of the pH or clay used, probably because the interlayers of clays are very acidic and HSCN formed does not reduce Fe(3+) to Fe(2+). For the interaction of thiocyanate with the clays, it was not possible to identify any potential compound formed. For the samples of bentonite and montmorillonite at pH 8.00 with cysteine, EPR spectroscopy showed that intensity of the lines due to Fe(3+) decreased because the reaction of Fe(3+)/cysteine. Intensity of EPR lines did not change when the samples of bentonite at pH 3.00 with and without cysteine were compared. These results are in accordance with those obtained using Mössbauer and FT-IR spectroscopy.

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In this paper is proposed a simultaneous pre-concentration procedure using cloud point extraction for the determination of copper and zinc in food samples employing sequential multi-element flame atomic absorption spectrometry (FS-FAAS). The reagent used is 1-(2-pyridylazo)-2-naphthol (PAN) and the micellar phase is obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The optimization step was performed using Box-Behnken design for three factors: solution pH, reagent concentration and buffer concentration. A multiple response function was established in order to get an experimental condition for simultaneous extraction of copper and zinc. Under the optimized experimental conditions, the method allows the determination of copper with a limit of detection (3sigma(b)/S, LOD) of 0.1 microg L(-1), precision expressed as relative standard deviation (R.S.D.) of 2.1 and 1.3% (N=10), for copper concentrations of 10 and 50 microg L(-1), respectively. Zinc is determined with a LOD of 0.15 microg L(-1) and precision as R.S.D. of 2.7 and 1.7% for concentrations of 10 and 50 microg L(-1), respectively. The enhancement factors obtained were 36 and 32 for copper and zinc, respectively. The accuracy was assessed by analysis of certified reference materials, namely, SRM 1567a - Wheat Flour and SRM 8433 - Corn Bran from National Institute of Standards & Technology and BCR 189-wholemeal flour from Institute of Reference Materials and Measurements. The method was applied to the determination of copper and zinc in oats, powdered chocolate, corn flour and wheat flour samples. The copper content in the samples analyzed varied from 1.14 to 3.28 microg g(-1) and zinc from 8.7 to 22.9 microg g(-1).

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In the present paper, the adsorption of amino acids (Ala, Met, Gln, Cys, Asp, Lys, His) on clays (bentonite, kaolinite) was studied at different pH (3.00, 6.00, 8.00). The amino acids were dissolved in seawater, which contains the major elements. There were two main findings in this study. First, amino acids with a charged R group (Asp, Lys, His) and Cys were adsorbed on clays more than Ala, Met and Gln (uncharged R groups). However, 74% of the amino acids in the proteins of modern organisms have uncharged R groups. These results raise some questions about the role of minerals in providing a prebiotic concentration mechanism for amino acids. Several mechanisms are also discussed that could produce peptide with a greater proportion of amino acids with uncharged R groups. Second, Cys could play an important role in prebiotic chemistry besides participating in the structure of peptides/proteins. The FT-IR spectra showed that the adsorption of amino acids on the clays occurs through the amine group. However, the Cys/clay interaction occurs through the sulfhydryl and amine groups. X-ray diffractometry showed that pH affects the bentonite interlayer, and at pH 3.00 the expansion of Cys/bentonite was greater than that of the samples of ethylene glycol/bentonite saturated with Mg. The Mössbauer spectrum for the sample with absorbed Cys showed a large increase ( approximately 20%) in ferrous ions. This means that Cys was able to partially reduce iron present in bentonite. This result is similar to that which occurs with aconitase where the ferric ions are reduced to Fe 2.5.

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Vanadium is recognized worldwide as the most abundant metallic constituent in petroleum. It is causing undesired side effects in the refining process, and corrosion in oil-fired power plants. Consequently, it is the most widely determined metal in petroleum and its derivatives. This paper offers a critical review of analytical methods based on atomic spectrometric techniques, particularly flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ET AAS), inductively coupled plasma optical emission spectrometry (ICP OES), inductively coupled plasma mass spectrometry (ICP-MS). In addition an overview is provided of the sample pretreatment and preparation procedures for vanadium determination in petroleum and petroleum products. Also included are the most recent studies about speciation and fractionation analysis using atomic spectrometric techniques.

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In the present paper, a minicolumn of polyurethane foam loaded with 4-(2-pyridylazo)-resorcinol (PAR) is proposed as pre-concentration system for cadmium determination in drinking water samples by flame atomic absorption spectrometry. The optimization step was performed using two-level full factorial design and Doehlert matrix, involving the variables: sampling flow rate, elution concentration, buffer concentration and pH. Using the established experimental conditions in the optimization step of: pH 8.2, sampling flow rate 8.5 mL min(-1), buffer concentration 0.05 mol L(-1) and elution concentration of 1.0 mol L(-1), this system allows the determination of cadmium with detection limit (LD) (3sigma/S) of 20.0 ng L(-1) and quantification limit (LQ) (10sigma/S) of 64 ng L(-1), precision expressed as relative standard deviation (R.S.D.) of 5.0 and 4.7% for cadmium concentration of 5.0 and 40.0 microg L(-1), respectively, and a pre-concentration factor of 158 for a sample volume of 20.0 mL. The accuracy was confirmed by cadmium determination in the standard reference material, NIST SRM 1643d trace elements in natural water. This procedure was applied for cadmium determination in drinking water samples collected from Salvador City, Bahia, Brazil. For five samples analyzed, the achieved concentrations varied from 0.31 to 0.86 microg L(-1).

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Chocolate is a complex sample with a high content of organic compounds and its analysis generally involves digestion procedures that might include the risk of losses and/or contamination. The determination of copper in chocolate is important because copper compounds are extensively used as fungicides in the farming of cocoa. In this paper, a slurry-sampling flame atomic-absorption spectrometric method is proposed for determination of copper in powdered chocolate samples. Optimization was carried out using univariate methodology involving the variables nature and concentration of the acid solution for slurry preparation, sonication time, and sample mass. The recommended conditions include a sample mass of 0.2 g, 2.0 mol L(-1) hydrochloric acid solution, and a sonication time of 15 min. The calibration curve was prepared using aqueous copper standards in 2.0 mol L(-1) hydrochloric acid. This method allowed determination of copper in chocolate with a detection limit of 0.4 microg g(-1) and precision, expressed as relative standard deviation (RSD), of 2.5% (n = 10) for a copper content of approximately 30 microg g(-1), using a chocolate mass of 0.2 g. The accuracy was confirmed by analyzing the certified reference materials NIST SRM 1568a rice flour and NIES CRM 10-b rice flour. The proposed method was used for determination of copper in three powdered chocolate samples, the copper content of which varied between 26.6 and 31.5 microg g(-1). The results showed no significant differences with those obtained after complete digestion, using a t-test for comparison.

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In this work, a solid phase spectrophotometric method in association with flow injection analysis for formaldehyde determination has been developed with direct measurement of light-absorption in C(18) material. The 3,5-diacetyl-1,4-dihydrolutidine produced from the reaction between formaldehyde and fluoral P was quantitatively retained on C(18) support and the spectrophotometric detection was performed simultaneously at 412nm. The retained complex was quickly eluted from C(18) material with the eluent stream consisting of a 50% (v/v) ethanol solution. The results showed that the proposed method is simple, rapid and the analytical response is linear in the concentration range of 0.050-1.5mgL(-1). The limit of detection was estimated as 30mugL(-1) and the R.S.D. 2.2% using a sample volume of 625muL. The system presented an analytical throughput of 20 determinations per hour. The method was successfully applied in the determination of formaldehyde in ethanol fuel.