cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.14279009
title: ADVANCED TECHNIQUES FOR THE DIFFERENTIATION OF ISOMERS BY MASS SPECTROMETRY

description: Mass spectrometry (MS) is a powerful and widespread technique but is inherently uncapable to differentiate species with same m/z ratio. For this reason, many classical approaches were developed based on differential fragmentation patterns in tandem MS. More recently, new techniques for isomer identification in MS were developed, and we highlight the photodissociation techniques that will be discussed in this review. This photodissociation techniques explore the selective activation of isomers to induce isomer specific dissociations in the gas-phase that depend on the spectroscopic features of the isomers. If tunable radiation sources are available, this selective activation may be monitored as a function of the radiation wavelength, allowing the acquisition of vibrational or UV-Vis spectra of the isolated ions, making it possible to evaluate different isomers, protomers and even conformers by MS. These photodissociation techniques are even more powerful when coupled to ion mobility techniques, that will be briefly discussed. Because these techniques enhance the fields and analytical applications where MS can be used, this review will discuss the classical MS methods for isomer differentiation that lead to the fundamentals of ion spectroscopy and selective ion activation, with emphasis on the vibrational ion spectroscopy.
DOI: 10.6084/m9.figshare.14279009.v1
title: ADVANCED TECHNIQUES FOR THE DIFFERENTIATION OF ISOMERS BY MASS SPECTROMETRY

description: Mass spectrometry (MS) is a powerful and widespread technique but is inherently uncapable to differentiate species with same m/z ratio. For this reason, many classical approaches were developed based on differential fragmentation patterns in tandem MS. More recently, new techniques for isomer identification in MS were developed, and we highlight the photodissociation techniques that will be discussed in this review. This photodissociation techniques explore the selective activation of isomers to induce isomer specific dissociations in the gas-phase that depend on the spectroscopic features of the isomers. If tunable radiation sources are available, this selective activation may be monitored as a function of the radiation wavelength, allowing the acquisition of vibrational or UV-Vis spectra of the isolated ions, making it possible to evaluate different isomers, protomers and even conformers by MS. These photodissociation techniques are even more powerful when coupled to ion mobility techniques, that will be briefly discussed. Because these techniques enhance the fields and analytical applications where MS can be used, this review will discuss the classical MS methods for isomer differentiation that lead to the fundamentals of ion spectroscopy and selective ion activation, with emphasis on the vibrational ion spectroscopy.
DOI: 10.6084/m9.figshare.14279012.v1
title: ANALYSIS OF THE ABSTRACTS PRESENTED AT THE COORDINATED SESSIONS OF THE TEACHING AREA AT THE ANNUAL MEETINGS OF THE BRAZILIAN CHEMICAL SOCIETY

description: This article analyzes the abstracts accepted and presented at the Coordinated Sessions of the teaching area at the Annual Meetings of the Brazilian Chemical Society. The research is characterized as qualitative of bibliographic type, having as the source of information the abstracts book of the last 10 editions (2010-2019) of the event. Through the texts, were analyzed: the amount of abstracts; year of presentation; Brazilian geographic region; number of productions by Higher Education Institutions; academic background of the first authors; thematic focus of the abstracts; level of education discussed in the abstract; and chemical knowledge present in the productions. In all, 121 abstracts were analyzed. The results indicated non-continuous production from a temporal point of view in relation to the total of abstracts, the predominance of abstracts from the Southeast region, a parity between USP and UFG institutions about the total amount of texts, and a great diversity of thematic focus, showing new research trends and the decentralization of studies focused on Chemistry Teaching. We conclude that the area of Chemistry Teaching has much to be explored, since there are still issues that are little discussed by chemical educators.
DOI: 10.6084/m9.figshare.14279016
title: EVALUATION OF THE RELATIVE PROTECTION FACTOR OF ROSEMARY EXTRACT IN BIODIESEL IN THE PRESENCE OF TRANSITION METAL IONS

description: Biodiesel contains unsaturated methyl esters making it susceptible to oxidation reaction. Among the factors that cause oxidative instability is the contamination by transition metal ions that in small quantities catalyze the oxidation reaction. The objective of this work was to evaluate the relative protection factor of rosemary extract, in biodiesel, in the presence of transition metal ions. Chromatographic analysis and characterization of biodiesel were performed as well as the quantification of total phenolic compounds and extract activity. The ions Cr3+, Co2+ and Fe2+, at a concentration of 3.95 x 10-3 mol L-1, were added to the biodiesel with and without rosemary extract. The samples were submitted to the Rancimat test and to infrared region analyses. The infrared region spectra of the samples with Cr3+ are in accordance with the least catalytic power of this ion under the biodiesel oxidation. Samples with Co2+ ions, without extract, presented bands of aldehydes, and samples with Fe2+ ions show the formation of peroxide radicals, without rosemary extract at 48h. The antioxidant effect of the extract in biodiesel is observed by the reduction of the induction period of the samples. The relative protection factor proved to be a good tool to evaluate its efficiency.
DOI: 10.6084/m9.figshare.14279012
title: ANALYSIS OF THE ABSTRACTS PRESENTED AT THE COORDINATED SESSIONS OF THE TEACHING AREA AT THE ANNUAL MEETINGS OF THE BRAZILIAN CHEMICAL SOCIETY

description: This article analyzes the abstracts accepted and presented at the Coordinated Sessions of the teaching area at the Annual Meetings of the Brazilian Chemical Society. The research is characterized as qualitative of bibliographic type, having as the source of information the abstracts book of the last 10 editions (2010-2019) of the event. Through the texts, were analyzed: the amount of abstracts; year of presentation; Brazilian geographic region; number of productions by Higher Education Institutions; academic background of the first authors; thematic focus of the abstracts; level of education discussed in the abstract; and chemical knowledge present in the productions. In all, 121 abstracts were analyzed. The results indicated non-continuous production from a temporal point of view in relation to the total of abstracts, the predominance of abstracts from the Southeast region, a parity between USP and UFG institutions about the total amount of texts, and a great diversity of thematic focus, showing new research trends and the decentralization of studies focused on Chemistry Teaching. We conclude that the area of Chemistry Teaching has much to be explored, since there are still issues that are little discussed by chemical educators.
DOI: 10.6084/m9.figshare.14279016.v1
title: EVALUATION OF THE RELATIVE PROTECTION FACTOR OF ROSEMARY EXTRACT IN BIODIESEL IN THE PRESENCE OF TRANSITION METAL IONS

description: Biodiesel contains unsaturated methyl esters making it susceptible to oxidation reaction. Among the factors that cause oxidative instability is the contamination by transition metal ions that in small quantities catalyze the oxidation reaction. The objective of this work was to evaluate the relative protection factor of rosemary extract, in biodiesel, in the presence of transition metal ions. Chromatographic analysis and characterization of biodiesel were performed as well as the quantification of total phenolic compounds and extract activity. The ions Cr3+, Co2+ and Fe2+, at a concentration of 3.95 x 10-3 mol L-1, were added to the biodiesel with and without rosemary extract. The samples were submitted to the Rancimat test and to infrared region analyses. The infrared region spectra of the samples with Cr3+ are in accordance with the least catalytic power of this ion under the biodiesel oxidation. Samples with Co2+ ions, without extract, presented bands of aldehydes, and samples with Fe2+ ions show the formation of peroxide radicals, without rosemary extract at 48h. The antioxidant effect of the extract in biodiesel is observed by the reduction of the induction period of the samples. The relative protection factor proved to be a good tool to evaluate its efficiency.
DOI: 10.6084/m9.figshare.14279018
title: SYNTHESIS OF MATERIALS PRODUCED FROM SPENT BATTERIES WITH ENVIRONMENTAL APPLICATION

description: In this work, alkaline and nickel-metal hydride spent batteries were used as precursors of metals for the synthesis of polymetallic materials. These materials were synthesized via chemical reduction. Materials produced from nickel-metal hydride spent batteries (PM-NiMH) have a nanometric size, whereas the alkaline spent batteries (PM-Alk) have a micrometric size. PM-NiMH consists mainly of Ni, Co, and Cu and the PM-Alk consists mainly of Mn and Zn. The surface areas of PM-NiMH and PM-Alk were 82 m2g-1 and 109 m2 g-1, respectively. The synthesized materials were applied in the removal of reactive blue dye 4 (RB4). Parameters such as initial pH of the system, dose of the materials, and initial concentration of the dye were optimized. For both materials, the removal capacity of RB4 was constant over a wide pH range of (4-10). The removal capacity increases with the decrease of the materials dose and increase of the dye concentration until saturation of the active sites. The RB4 removal by PM-NiMH occurs by adsorption and degradation processes, whereas PM-Alk occurs only by adsorptive processes. The RB4 removal process follows the Langmuir adsorption isotherm model with maximum removal capacities of 331 and 127 mg g-1 for PM-NiMH and PM-Alk, respectively.
DOI: 10.6084/m9.figshare.14279018.v1
title: SYNTHESIS OF MATERIALS PRODUCED FROM SPENT BATTERIES WITH ENVIRONMENTAL APPLICATION

description: In this work, alkaline and nickel-metal hydride spent batteries were used as precursors of metals for the synthesis of polymetallic materials. These materials were synthesized via chemical reduction. Materials produced from nickel-metal hydride spent batteries (PM-NiMH) have a nanometric size, whereas the alkaline spent batteries (PM-Alk) have a micrometric size. PM-NiMH consists mainly of Ni, Co, and Cu and the PM-Alk consists mainly of Mn and Zn. The surface areas of PM-NiMH and PM-Alk were 82 m2g-1 and 109 m2 g-1, respectively. The synthesized materials were applied in the removal of reactive blue dye 4 (RB4). Parameters such as initial pH of the system, dose of the materials, and initial concentration of the dye were optimized. For both materials, the removal capacity of RB4 was constant over a wide pH range of (4-10). The removal capacity increases with the decrease of the materials dose and increase of the dye concentration until saturation of the active sites. The RB4 removal by PM-NiMH occurs by adsorption and degradation processes, whereas PM-Alk occurs only by adsorptive processes. The RB4 removal process follows the Langmuir adsorption isotherm model with maximum removal capacities of 331 and 127 mg g-1 for PM-NiMH and PM-Alk, respectively.
DOI: 10.6084/m9.figshare.14279021
title: STUDY OF SPECTROPHOTOMETRIC CHARACTERISTICS OF THE CHARGE TRANSFER COMPLEX OF TAURINE DRUG WITH 7,7,8,8-TETRACYANOQUINODIMETHANE

description: A new spectrophotometric method was developed for the determination of taurine using 7,7,8,8-tetracyanoquinodimethane (TCNQ). The method was based on the formation of charge transfer (CT) complex of this drug as n-electron donor with the π-acceptor TCNQ. TCNQ was found to react with taurine to produce a kind of yellow complex. The spectrum obtained for taurine/TCNQ system showed the maximum absorption band at a wavelength of 420 nm. The formation of such complex was also confirmed by both infrared and 1H NMR measurements. Different variables affecting the reaction were studies and optimized. Beer’s law was obeyed in a concentration limit of 1~9 µg mL-1 for taurine. R.S.D. was less than 1.5%, and average recovery was over 100.3%. The stoichiometry of the complex was found to be 1:1 ratio by Job’s and straight line methods between the donor and the acceptor. The thermodynamic standard reaction quantities of the complex between the donor and the acceptor were estimated. The developed method could be applied successfully for the determination of the studied compound in the pharmaceutical dosage form with a good precision and accuracy compared to official and reported method as revealed by t- and F-tests.
DOI: 10.6084/m9.figshare.14279021.v1
title: STUDY OF SPECTROPHOTOMETRIC CHARACTERISTICS OF THE CHARGE TRANSFER COMPLEX OF TAURINE DRUG WITH 7,7,8,8-TETRACYANOQUINODIMETHANE

description: A new spectrophotometric method was developed for the determination of taurine using 7,7,8,8-tetracyanoquinodimethane (TCNQ). The method was based on the formation of charge transfer (CT) complex of this drug as n-electron donor with the π-acceptor TCNQ. TCNQ was found to react with taurine to produce a kind of yellow complex. The spectrum obtained for taurine/TCNQ system showed the maximum absorption band at a wavelength of 420 nm. The formation of such complex was also confirmed by both infrared and 1H NMR measurements. Different variables affecting the reaction were studies and optimized. Beer’s law was obeyed in a concentration limit of 1~9 µg mL-1 for taurine. R.S.D. was less than 1.5%, and average recovery was over 100.3%. The stoichiometry of the complex was found to be 1:1 ratio by Job’s and straight line methods between the donor and the acceptor. The thermodynamic standard reaction quantities of the complex between the donor and the acceptor were estimated. The developed method could be applied successfully for the determination of the studied compound in the pharmaceutical dosage form with a good precision and accuracy compared to official and reported method as revealed by t- and F-tests.
DOI: 10.6084/m9.figshare.14279014
title: SEMIOTIC MODEL FOR READING INSCRIPTIONS: APPLICATION IN CHEMISTRY EDUCATION

description: Inscriptions - graphs, diagrams, photographs, tables, and so forth - are central to scientific practice. In this study, a semiotic model was used to evaluate the reading of inscriptions by undergraduate chemistry students when giving oral presentations based on original research articles about environmental chemistry. Results revealed that the model helps to identify the extension of the adequacy of using inscriptions by the students in communicative situations. Potentialities and limitations of the model for chemistry education are discussed.
DOI: 10.6084/m9.figshare.14279024
title: VALIDATION OF ANALYTICAL METHODS IN A PHARMACEUTICAL QUALITY SYSTEM: AN OVERVIEW FOCUSED ON HPLC METHODS

description: Analytical validation has fundamental importance in the scope of Good Manufacturing Practice (GMP) for pharmaceutical products since it establishes scientific evidence that an analytical procedure provides reliable results. However, even with validation guidelines available it is very common to observe misunderstandings in the execution of validation and data interpretation. The misguided approaches of validation guidelines, allied with a disregard for the peculiarities of the analytical techniques, the nature of the sample, and the analytical purpose, have significantly contributed to oversights in analytical validation. This work aims to present a critical overview of the validation process in pharmaceutical analysis, addressing relevant aspects of various analytical performance parameters, their different means of accomplishment and limitations in face of the analytical techniques, the nature of the sample, and the analytical purpose. To help in the planning and execution of the validation process, some case studies are discussed, mainly in the area of high-performance liquid chromatography (HPLC).
DOI: 10.6084/m9.figshare.14279027
title: DETERMINATION OF FOUR ARSENIC SPECIES IN ALGAE BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY COUPLED WITH HYDRIDE GENERATION ATOMIC FLUORESCENCE SPECTROMETRY

description: A rapid method has been developed for the determination of silver arsenite As(III), dimethylated arsenic DMA, monomethylated arsenic MMA, and arsenate As(V) in algae sample using liquid chromatography coupled with hydride generation atomic fluorescence spectrometry (LC-HG-AFS). Types, flow rate and pH of mobile phase were optimized. Under the optimal conditions, there were good linear relationships in the range of 0 -200 µg L-1 with correlation coefficients larger than 0.9995. The limits of detection and quantification of As(III), DMA, MMA, and As(V) were 0.005- 0.010 mg kg-1 and 0.019-0.034 mg kg-1, respectively. The recoveries at three spiked levels of 0.02, 0.5 and 1.0 mg kg-1 were in the range of 93-105 % with relative standard deviations (RSD, n=6) of 3.6%-6.2%. The proposed method was successfully applied in the determinaton of four arsenic species in algae sample. The developed method is simple, higher precision, stable data collection, and shorter separation time, and could be applied in the speciation and study of arsenic species in algae.
DOI: 10.6084/m9.figshare.14279027.v1
title: DETERMINATION OF FOUR ARSENIC SPECIES IN ALGAE BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY COUPLED WITH HYDRIDE GENERATION ATOMIC FLUORESCENCE SPECTROMETRY

description: A rapid method has been developed for the determination of silver arsenite As(III), dimethylated arsenic DMA, monomethylated arsenic MMA, and arsenate As(V) in algae sample using liquid chromatography coupled with hydride generation atomic fluorescence spectrometry (LC-HG-AFS). Types, flow rate and pH of mobile phase were optimized. Under the optimal conditions, there were good linear relationships in the range of 0 -200 µg L-1 with correlation coefficients larger than 0.9995. The limits of detection and quantification of As(III), DMA, MMA, and As(V) were 0.005- 0.010 mg kg-1 and 0.019-0.034 mg kg-1, respectively. The recoveries at three spiked levels of 0.02, 0.5 and 1.0 mg kg-1 were in the range of 93-105 % with relative standard deviations (RSD, n=6) of 3.6%-6.2%. The proposed method was successfully applied in the determinaton of four arsenic species in algae sample. The developed method is simple, higher precision, stable data collection, and shorter separation time, and could be applied in the speciation and study of arsenic species in algae.
DOI: 10.6084/m9.figshare.14279030
title: OXIDATIVE STABILITY AND COLD FILTER PLUGGING POINT OF BIODIESEL BLENDS DERIVED FROM FATS AND SOY OIL

description: Biodiesel made from oils is rich in polyunsaturated fatty acids methyl esters, and, consequently, presents high tendency to oxidize. Biodiesel made from fats, on the other hand, is mainly comprised by saturated chains. Although it is highly stable, they easily crystalize at low temperatures. Blends from both can exhibit optimized properties. In this work, oxidative stability, expressed by induction period (IP), and cold filter plugging point (CFPP) of blends from palm, palm kernel, babassu, tallow or lard biodiesels with soy one were measured. Biodiesel samples were prepared by two steps transesterification methodology with KOH catalysis followed by H2SO4. IP increases, as the fat biodiesel content in the blend is higher, as expected. Blends comprised by 60% of fat biodiesel by volume had their IP increased from 1.5 (lard) to 2 times (palm kernel), compared to soy one. At this level, IP was found 8 h or higher, except for palm, which 80% was required. CFPP was observed at 8 °C or lower for the blends containing up to 60% of all the fat biodiesel, except for the palm one, which a 20% content must not be surpassed. Palm kernel 80% biodiesel blend reached the Brazilian specification, that is, IP higher than 12 h and CFPP lower than 5 °C.
DOI: 10.6084/m9.figshare.14279030.v1
title: OXIDATIVE STABILITY AND COLD FILTER PLUGGING POINT OF BIODIESEL BLENDS DERIVED FROM FATS AND SOY OIL

description: Biodiesel made from oils is rich in polyunsaturated fatty acids methyl esters, and, consequently, presents high tendency to oxidize. Biodiesel made from fats, on the other hand, is mainly comprised by saturated chains. Although it is highly stable, they easily crystalize at low temperatures. Blends from both can exhibit optimized properties. In this work, oxidative stability, expressed by induction period (IP), and cold filter plugging point (CFPP) of blends from palm, palm kernel, babassu, tallow or lard biodiesels with soy one were measured. Biodiesel samples were prepared by two steps transesterification methodology with KOH catalysis followed by H2SO4. IP increases, as the fat biodiesel content in the blend is higher, as expected. Blends comprised by 60% of fat biodiesel by volume had their IP increased from 1.5 (lard) to 2 times (palm kernel), compared to soy one. At this level, IP was found 8 h or higher, except for palm, which 80% was required. CFPP was observed at 8 °C or lower for the blends containing up to 60% of all the fat biodiesel, except for the palm one, which a 20% content must not be surpassed. Palm kernel 80% biodiesel blend reached the Brazilian specification, that is, IP higher than 12 h and CFPP lower than 5 °C.
DOI: 10.6084/m9.figshare.14279032
title: IMPROVING THE CATALYTIC FEATURES OF THE LIPASE FROM Rhizomucor miehei IMMOBILIZED ON CHITOSAN-BASED HYBRID MATRICES BY ALTERING THE CHEMICAL ACTIVATION CONDITIONS

description: The lipase from Rhizomucor miehei (RML) has been immobilized on chitosan-based hybrid (sodium alginate or carrageenan) matrices activated with glycidol (GLY), epichlorohydrin (EPI) or glutaraldehyde (GLU) groups. Then, the properties of the different biocatalysts have been evaluated and compared with the soluble RML. Thermal stability (at pH 7.0 and 60 °C) was significantly increased when compared to the soluble enzyme: 154-fold for chitosan 5.0% - GLU, 80-fold for chitosan 2.5% - carrageenan 2.5% - GLY and 93-fold for chitosan 2.5% - alginate 2.5% - EPI. The best biocatalyst preparation, which was 154-fold more stable than the soluble enzyme, was obtained when RML was immobilized on chitosan activated with glutaraldehyde 5.0% v/v. According to the results, it was concluded that RML immobilization on chitosan-based hybrid matrices using different chemistries greatly produced biocatalysts with different properties.
DOI: 10.6084/m9.figshare.14279034
title: IN SITU DRIFTS/MS STUDIES ON THE INTERACTION OF METHANOL AND ETHYL ACETATE OVER MG-LA CATALYST

description: The surface intermediates formed on the Mg-La catalyst (molar ratio 1:1) were studied through temperature-programmed desorption (TPD) and diffuse reflectance infrared Fourier transform spectroscopy coupled to mass spectrometry (DRIFTS-MS) using methanol (MeOH) and ethyl acetate (EA) as probe molecules. TPD results showed that the products formed from adsorbed MeOH were hydrogen and formaldehyde, whereas EA produced hydrogen, ethanol, and acetone. DRIFTS-MS of a MeOH and EA mixture results showed that methanol adsorbs as methoxy species on the catalyst surface, and EA adsorbs through the oxygen of carbonyl groups forming ethoxy and acetate species. The reaction of the adsorbed intermediate species resulted in the formation of methane, CO2 gas phase, ethanol, and methyl acetate. Also, methanol adsorbed preferentially on the basic site and EA in a dissociative form. Surface intermediates identification allowed to confirm that the Eley-Rideal type mechanism was predominant on the catalyst surface studied.