DISSERTAÇÃO DE MESTRADO - PROGRAMA DE PÓS-GRADUAÇÃO EM QUIMICA
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Item Desenvolvimento de sistemas à base de mesocarpo de babaçu e alginato de sódio como matriz carregadora do fármaco metronidazol(Universidade Federal do Maranhão, 2021-11-24) OLIVEIRA, Letícia Nascimento de; SANTANA, Sirlane Aparecida Abreu; http://lattes.cnpq.br/1052349578152491; SANTANA, Sirlane Aparecida Abreu; http://lattes.cnpq.br/1052349578152491; ALCÂNTARA, Ana Clécia Santos de; http://lattes.cnpq.br/3149929057352643; ROCHA, Jefferson AlmeidaThis work aimed to evaluate spheres based on sodium alginate and starch extracted from babassu mesocarp as a matrix for the controlled release of the drug metronidazole. The starch was obtained by water extraction method and the same was synthesized using chloroacetic acid as etherifying agent, resulting in carboxymethylamides with degrees of substitution (GS) of 0.15 ± 0.01 and 0.3 ± 0.01. The solubility and intumescence study of the starch and carboxymethylamide samples showed changes in the properties after modification. The study of amylose content of native and modified starch using colorimetric method showed a large variation in amylose content, from 28.0 ± 0.89, 4.70 ± 0.21 and 3.32 ± 0.04, proving the reduction of the macromolecule after modification. The starch and carboxymethyl starch samples were characterized by FTIR, SEM and DSC. The drug metronidazole was incorporated into sodium alginate/ babassu mesocarp starch and sodium alginate/carboxymethyl starch polymeric matrices, obtaining spheres through ionotropic gelation in a CaCl2 solution. The interaction between the polysaccharides and the incorporation of the drug were proven by FTIR and SEM results. Energy Dispersive Spectroscopy (EDS) analysis enabled the detection of elements such as Ca, Na, Cl and O, as well as the percentage changes that occurred after polymer mixing. A molecular absorption study in the ultraviolet region proved the presence of the drug metronidazole incorporated in the spheres. The study of intumescence and erosion of the spheres showed that the absorption capacity of the spheres was improved in the spheres containing the CMA, which also influenced the erosion that was decreased with the increase in the degree of substitution of the anionic starch. The encapsulation efficiency (EE) varied according to the composition of the spheres. For the alginate and alginate/raw starch spheres the EE was 36.0% ± 5.40 and 53% ± 4.23 and for the alginate/carboxymethyl starch spheres, the EE obtained was 69.57% ± 3.94 and 73.89% ± 5.22. The release assays demonstrated that in gastric medium, the spheres showed a low dissolution rate, suggesting gastroresistance at low pH. In simulated enteric medium, the ALG.CMA2 samples (GS = 0.3) maintained the same dissolution rate until the end of the experiment, suggesting a control in the release of metronidazole. Thus, it was possible to prove that the samples containing carboxymethyl starch are promising delivery systems for the sustained release of the drug under gastrointestinal conditions.Item Estudo teórico da interação entre nanotubos de carbono, nitreto de boro e nitreto de gálio com compostos cisplatina e cisplatina-metila usados no tratamento de câncer(Universidade Federal do Maranhão, 2021-06-25) PEREIRA, Jurandir Santos; VARELA JÚNIOR, Jaldyr de Jesus Gomes; http://lattes.cnpq.br/5125904184711352; VARELA JUNIOR, Jaldyr de Jesus Gomes; http://lattes.cnpq.br/5125904184711352; BEZERRA, Cícero Wellington Brito; http://lattes.cnpq.br/1474300723265204; FIGUEIREDO, Gilvan Pereira de; http://lattes.cnpq.br/3730724432445516This work presents a theoretical study on carbon nanotubes, boron nitride and Thrush nitride interacting with cisplatin compounds and a cisplatin-methyl non branched chain derivative, through simulations of first principles, based on the theory of density functional (FTD). Simulation calculations were performed in the SIESTA computer program. The structural, energetic and electronic properties of the cisplatin and cisplatin-methyl molecule, adsorbed internally and externally in carbon nanotubes (CNT) composed of 96 atoms, Boron nitride (BN) and Galium nitride (GaN) both composed of equal amounts of atoms, were analyzed. All possible stable conformers of the drugs were investigated by means of geometry optimizations at the theory level, using as a DZP base for platinum. The results show that the electronic properties of the nanotubes are affected by adsorption of the cisplatin and cisplatin methyl molecules. After internal and external adsorption of cisplatin and cisplatin methyl internal adsorption, it was observed that the energy gap decreased in all nanotubes due to the levels introduction of of defects in the gap region. In the pure CNT the gap was 1.34 eV, when it interacts with cisplatin began to have a gap of 1.28 eV (internal and external) and with cisplatin-methyl the gap went to 1.26 eV. In pure GaN the gap, which was 2.47 eV, when adsorbed to cisplatin, internally passes to 2.14 eV and externally passes to 1.60 eV with cisplatin-methyl passes to 2.26 eV. In pure BN, the gap, which was 4.53 eV, with cisplatin inclusion and then cisplatin methyl, both passed to 2.87 eV and when adsorbed externally with cisplatin passes to 2.73 eV. In addition, quantum calculations of internal and external adsorption verified that all single-walled CNT, BN and GaN nanotubes adsorbed the cisplatin and cisplatin-methyl molecules spontaneously through the chemisorption process.Item Análise por injeção em batelada de glicose assistida fotoeletroquimicamente explorando uma plataforma à base de Cu2O(Universidade Federal do Maranhão, 2021-03-05) CARDOSO, Elenilse Rodrigues; DAMOS, Flávio Santos; http://lattes.cnpq.br/0915687070195770; DAMOS, Flávio Santos; http://lattes.cnpq.br/0915687070195770; BEZERRA, Cícero Wellington Brito; http://lattes.cnpq.br/1474300723265204; RICHTER, Eduardo Mathias; http://lattes.cnpq.br/0310068697989712This work describes the development of a photoelectrochemical system for glucose quantification, exploring a photoelectrochemical assisted batch injection analysis (BIA). The BIA cell was coupled to a LED lamp in order, to control the incidence of light on the p-Cu2O/n-Cu2O/FTO photoactive platform. Physical and electrochemical characteristics of Cu2O films were investigated by X-ray diffraction, Raman spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The p-Cu2O/n-Cu2O/FTO photoelectrode coupled to PEC-BIA cellpresented a linear response from 10 to 1000 μmol L-1 , detection limit of 4 μmol L-1 and sensitivity of 0.768 ± 0.011 μAμmol L-1 . Average recovery value of 96% was evaluatedto the determination of glucose in an artificial saliva sample, which indicates a promising performance for the determination and quantification of glucose in real samples.Item Obtenção e fracionamento de ésteres metílicos de ácidos graxos a partir do óleo de coco ariri (Syagrus cocoides martius)(Universidade Federal do Maranhão, 2020-12-09) BASTOS, Fernanda Carneiro; MACIEL, Adeilton Pereira; 929354274-91; http://lattes.cnpq.br/4957262830051547; MACIEL, Adeilton Pereira; 929354274-91; http://lattes.cnpq.br/4957262830051547; CAVALCANTE, Kiany Sirley Brandão Cavalcante; http://lattes.cnpq.br/3810732989135120; ROCHA, Claudia Quintino da; http://lattes.cnpq.br/5609489233382242Despite the great diversity of palm trees (Arecaceae) there is still no data on many of them, for example ariri. The ariri is of the Syagrus genus and has fruits composed of oily almonds and its application is mainly restricted to popular use. This work aims to evaluate the ariri coconut almond oil, as to the extraction method and as a raw material for obtaining enriched fractions of methyl esters of fatty acids. Initially, the species used was identified. The extraction of almond oil was performed in cold and hot way, with fruits collected in a dry and rainy season; and analyzed as to the yield and physical-chemical parameters.The esters were obtained by alkaline transesterification, under magnetic stirring at 60 ° C (333, 15 F), 1:18 m / m molar ratio (oil: methanol) and 1% KOH catalyst (% oil mass); for 1 hour. The fractionation of the esters was performed by liquid column chromatography, packed with silica gel 60, mobile phase hexane / ethyl acetate; accompanied by Thin Layer Chromatography and Gas Chromatography coupled to Mass Spectrometer. The species was identified as Syagruscocoides Martius. The extractions proved to be efficient and without significant changes due to the method used. As for the collection period, the oil from fruits obtained in the dry period showed better quality. Several fractions were obtained among them pure fraction of the methyl ester of lauric acid and mixtures containing 2-6 esters, with 62.7–96.95% of the methyl ester of lauric acid. This result accredits coconut ariri as an excellent raw material for obtaining new high purity standards and as a raw material for application in various products.Item Estudo da interação de FeCl3 e CrO3 nas superfícies dos Nanotubos de InN e GaP utilizando a Teoria do Funcional da Densidade(Universidade Federal do Maranhão, 2019-08-02) SILVA, Caio Vinícius Caetano Ribeiro da; GUERINI, Silvete Coradi; 59914424015; http://lattes.cnpq.br/0527275499843168; VARELA JÚNIOR, Jaldyr de Jesus Gomes; 666873223-20; http://lattes.cnpq.br/5125904184711352; VARELA JÚNIOR, Jaldyr de Jesus Gomes; 666873223-20; http://lattes.cnpq.br/5125904184711352; BEZERRA, Cícero Wellington Brito; http://lattes.cnpq.br/1474300723265204; FIGUEIREDO, Gilvan Pereira deThis work presents a theoretical study about the nanotubes of InN and GaP interacting with the compounds FeCl3 and CrO3 through first principles simulations, based on density functional theory (DFT). The calculations were performed with the SIESTA code. Structural, energetic and electronic properties of the FeCl3 and CrO3 compounds adsorbed on the InN and GaP nanotubes were analyzed. The results show that the electronic properties of both nanotubes are affected by the interaction of the FeCl3 and CrO3 compounds. After adsorption of FeCl3, it was observed that the energy gap decreased in both nanotubes, due to appearance of defect levels in the region of the energy gap, however when it was adsorbed internally to the GaP nanotube, the system presented a metallic character. With CrO3, there was an increase in the energy gap when it was adsorbed externally to the GaP nanotube, and in the other systems, the energy gap reduced due to displacements of the energy levels of the valence band. The calculations also indicate that both compounds, adsorbed inside and outside the InN and GaP nanotubes, interact through a chemical adsorption process. In addition, it was observed that when FeCl3 is adsorbed on the InN and GaP nanotubes, it acts as a Lewis acid, whereas CrO3 acts as a Lewis base. A study was also performed about the relativistic effects on the In atom of the InN nanotube, and it was verified through comparisons with results found in the literature that the relativistic correction better describes the electronic properties of this material, but does not alter the trends found in the studied systems.Item Desenvolvimento de um sistema para determinação de glicose usando análise por injeção em batelada assistida por fotoeletroquímica(Universidade Federal do Maranhão, 2019-03-22) SOARES, Leonardo Carvalho; DAMOS, Flávio Santos; 846255703-87; http://lattes.cnpq.br/0915687070195770; DAMOS, Flávio Santos; 846255703-87; http://lattes.cnpq.br/0915687070195770; SILVA, Iranaldo Santos da; http://lattes.cnpq.br/1281555528581499; ARAÚJO, Adriana Barbosa; http://lattes.cnpq.br/1008844766307732This work describes the development of a novel method for glucose detection exploiting a photoelectrochemical-assisted batch injection analysis cell designed and constructed with aid of 3D printer technology. The PEC-BIA cell was coupled to a LED lamp in order to control the incidence of light on the Cu2O/Ni(OH)2/FTO photoelectro-active platform. The electrochemical characteristics of Cu2O/Ni(OH)2/FTO photoelec-troactive platform were evaluated by cyclic voltammetry, amperometry and electro-chemical impedance spectroscopy. The PEC-BIA cell presented linear response range, limit of detection and sensitivity of 1 – 1000 μmol L-1, 0.59 mol L-1 and 0.578 A L mol-1, respectively. The PEC-BIA method has presented a mean value of the recovery values of 97.0 % to 102.0% when it was applied to glucose determination in artificial blood plasma samples which indicates the promising performance of the proposed sys-tem to determine glucose.Item Distribuição de agentes anti-incrustantes de 3ª geração em distintos compartimentos ambientais da região portuária de São Luís, Maranhão(Universidade Federal do Maranhão, 2019-02-18) VIANA, José Lucas Martins; ALMEIDA, Márcio Aurélio Pinheiro; 847653723-91; http://lattes.cnpq.br/2880967876823602; ALMEIDA, Márcio Aurélio Pinheiro; 847653723-91; http://lattes.cnpq.br/2880967876823602; NUNES, Gilvanda Silva; http://lattes.cnpq.br/5833210771020427; FRANCO, Teresa Cristina Rodrigues dos Santos; http://lattes.cnpq.br/6219897465386798Substances used in antifouling paints are important contaminants into the aquatic environment. Due to the high traffic of vessels, São Luís Island is subject to the presence of this type of contaminant. So, the aim of this work was to evaluate the presence and distribution of the antifouling biocides irgarol, diuron, DCPMU (diuron degradation product) and DMSA in marine water, sediment and interstitial water samples from coastal areas of São Luís, where vessel traffic take place. The analyses were performed by high-performance liquid chromatography coupled to mass spectrometry with electrospray ionization and single quadrupole mass analyzer (HPLC-ESI-SQ-MS). The analytes were extracted from sediment samples by vortex-assisted matrix solid-phase dispersion (VA-MSPD), in marine water a SPE protocol was applied and in interstitial waters, the methodology used was vortex-assisted dispersive liquid-liquid microextraction (VA-DLLME). The analytical parameters evaluated were suitable for trace analysis of these substances in the matrices studied, except for DMSA in marine water. Diuron, DCPMU and irgarol were detected in all matrices studied, while DMSA was detected only in interstitial waters. Diuron was the predominant biocide in sediments, but it was detected in only one marine water sampling site and in three interstitial water sampling sites. DCPMU, on the other hand, was the most detected analyte in interstitial water samples, despite having a low detection frequency in the other matrices studied. The predominance of irgarol was observed in marine water, where it showed a 100% detection frequency, but its levels in sediment samples were much higher. Distribution coefficients (Kd) and organic carbon/water partitioning coefficients (Koc) between sea water/sediment and interstitial water/sediment showed that irgarol and diuron had preferential partitioning in sediments, whereas DCPMU and DMSA had partitioning in water interstitial. In all cases, the partitioning in marine water was low. The levels of irgarol and diuron represented a risk for marine biota, according to environmental risk limits and ecotoxicological tests present in the literature.Item Síntese e caracterização de compósito carbonáceo de magnetita para aplicação como fotocalisador(Universidade Federal do Maranhão, 2018-09-28) COSTA, Fernanda Rodrigues Torres da; MACIEL, Adeilton Pereira; 929354274-91; http://lattes.cnpq.br/4957262830051547; MACIEL, Adeilton Pereira; 929354274-91; http://lattes.cnpq.br/4957262830051547; CAVALCANTE, Kiany Sirley Brandão; http://lattes.cnpq.br/3810732989135120; DAMOS, Flávio Santos; http://lattes.cnpq.br/0915687070195770In the present work a carbonaceous composite of magnetite obtained from the coconut ariri biomass was prepared by the wet impregnation method with iron chloride III for the degradation of the rhodamine B. The composite was characterized by X-Ray Diffraction), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray energy dispersion spectroscopy (EDX), Raman Spectroscopy and Thermogravimetric analysis of biomass. The obtained compound presented magnetic characteristics, where such property facilitates the removal of the material in a reaction mixture. With the XRD technique, one can observe the presence of phases referring to a carbonaceous material with phase of magnetite. The infrared spectra confirmed the presence of the vibrations of the main bonds present in the in natura biomass and the obtained composite. The micrographs illustrated a heterogeneous material. The EDX technique shows that the composite is composed primarily of carbon, iron, and oxygen. The RAMAN spectroscopy demonstrates that the composite obtained has characteristics of carbonaceous compound. In the thermal analysis of the biomass, it was observed the main losses of mass, referring to the decomposition of the lignino-cellulosic material, as well as the influence of iron chloride. After characterizing this carbonaceous compound was applied in the degradation of rhodamine B, where the photocatalytic activity was evaluated by light irradiation in rhodamine solution. The photodegradation of the organic dye reached 80% in maximum time of 140 min light irradiation.Item Avaliação da potencialidade do eletrodo compósito à base de grafite/poliuretana modificado com azul da Prússia para determinação de íons k+ em biodiesel(Universidade Federal do Maranhão, 2018-03-02) COSTA, Ediani Paurá; MARQUES, Edmar Pereira; 032416453-04; http://lattes.cnpq.br/2468528554511482; MARQUES, Edmar Pereira; 032416453-04; http://lattes.cnpq.br/2468528554511482; SOUSA, Eliane Rodrigues de; http://lattes.cnpq.br/0356225771584504; AZEVEDO, Lorena Carvalho Martiniano de; http://lattes.cnpq.br/8536193616269377A composite electrode polyurethane graphite (GPU) modified with iron hexacyanoferrate (FeHCF), also known as Prussian Blue (PB), was used for the determination of K + ions in biodiesel samples. The surface of the electrode was coated with PB film by electrodeposition after 50 voltammetric cycles with a scanning speed of 50 mV.s-1 in a potential range of -0.3 to 1.2 V. As electrochemical measurements were performed in solution of potassium phosphate buffer 0.1 mol. L-1 (pH 7.0). The experimental parameters used in the application of the method using the differential pulse voltammetry technique were optimized by obtaining the following conditions: reservoir potential: 0.6 V, pulse amplitude: 50 mV and scanning speed of 5 mV. s-1. The interaction of the analyte with the GPU/PB electrode caused a linear decrease without current signal, which is allowed to extract quantitative values for the potassium concentration in the biodiesel samples of 6.97 x 10-5 ± 1.95 x 10-5 mol. L-1 for the interlaboratory test and 9.29 x 10-5 ± 1.02 x 10-5 mol. L-1 for the laboratory sample. The results were concordant statistically considering the Student's t-test for a confidence level of 95%. The CV values were lower than 25%, and the detection limit was 2.95 x 10-9 and 2.20 x 10-6 mol. L-1 for a certified and laboratory sample, respectively, showing a good accuracy and sensitivity of the proposed method.Item COMPLEXO NÍQUEL(II)-BIS(1,10-FENANTROLINA) SUPORTADO EM ÓXIDO DE GRAFENO REDUZIDO PARA A ELETRO-OXIDAÇÃO DE ETANOL.(Universidade Federal do Maranhão, 2017-09-19) SANTOS, José Ribamar Nascimento dos; MARQUES, Aldaléa Lopes Brandes; 076486263-49; http://lattes.cnpq.br/0121030502015990; MARQUES, Aldaléa Lopes Brandes; 076486263-49; http://lattes.cnpq.br/0121030502015990; CARDOSO, William da Silva; http://lattes.cnpq.br/7348480060195285; DAMOS, Flávio Santos; http://lattes.cnpq.br/0915687070195770The electro-oxidation of ethanol was evaluated on a pyrolytic graphite electrode (PGE) chemically modified with the nickel(II)-bis(1,10-phenanthroline) complex (Ni(II)(Phen)2) supported on reduced graphene oxide (RGO) (rGO/Ni(II)(Phen)2/PGE). The Ni(II)(Phen)2 complex, reduced graphene oxide (rGO) and the rGO/Ni(II)(Phen)2 composite were prepared and characterized by the techniques of Spectroscopy in the UV-Vis, Fourier Transform Infrared Spectroscopy and Diffraction of X-rays. The electrocatalytic activity of the material was evaluated by cyclic voltammetry and chronoamperometry. In alkaline solution, the voltamograms obtained for rGO/Ni(II)(Phen)2/PGE showed the formation of well defined redox peaks associated with the Ni(II)/Ni(III) redox couple. The results showed that the RGO/Ni(II)(Phen)2 composite significantly increases the electrocatalytic activity for ethanol oxidation compared to the electrode modified only with the Ni(II)(Phen)2 complex. Using the Laviron theory, the charge transfer rate constant (ks) and the electron transfer coefficient (α) of the electrode reaction were calculated to be 0.56 s-1 and 0.61, respectively. A investigation of the electro-oxidation of ethanol was performed by evaluating the effect of different parameters such as potential scan rate, OH- concentration and alcohol concentration. The chronoamperometric experiments were used to determine the diffusion coefficient of ethanol (D = 4.7 Χ 10-6 cm2 s-1) and the catalytic rate constant (kcat = 1.26 Χ 107 cm3 mol-1 s-1). The results obtained in this study clearly indicate the viability of rGO/Ni(II)(Phen)2/PGE as an electrocatalyst for ethanol oxidation.Item Blendas à base de quitosana e poliacrilamida revestidas com ZnO como catalisadores para a fotodegradação do azul de metileno(Universidade Federal do Maranhão, 2017-08-31) MAIA, Luziane Freire; BEZERRA, Cícero Wellington Brito; 311.559.103-97; http://lattes.cnpq.br/1474300723265204; ARAUJO, Adriana Barbosa; LUZ, Rita de CássiaTextile dyes are recognized as a serious environmental problem due the huge quantity discharged annually in water environments, and its dangerous health risks. Efficient and low cost methods for effluent treatment and recovery of impacted areas are necessary and increasingly researched. The photocatalytic degradation is one of these methods, and this work investigated the feasibility of photocatalytic degradation of the methylene blue (AM) dye from aqueous solutions (5 and 15 mgL-1) in the presence and absence of prepared catalysts (chitosanpolyacrylamide (QT-P), and chitosan-polyacrylamide doped with Zn, QT-P/ZnO). The chitosan and polyacrylamide interaction was studied as a function of the degree of deacetylation of chitosan (64, 82 and 90%), previously obtained from the deacetylation of chitin extracted from shrimp exoskeletons. The QT-P/ZnO heterostructures were characterized by FTIR, XRD and MEV. The photocatalysis experiments were performed considering the effects of pH, contact time and mass variation. AM samples were irradiated with mercury vapor lamp (black light,50W mm-2) and photocatalysis was monitored by UV-Vis spectrophotometry, at the peak wavelength of 665 nm. The results indicated that QT-P interaction is favored by deacetylation. All the materials prepared showed a catalytic effect, but the heteroestructure obtained from the chitosan with the highest degree of deacetylation (QTC-P/ZnO) was the most efficient: 99.2% (AM, 15 mg L-1, 50 min) and 99.8% (AM, 5 mg L-1, 20 min).Item Compósitos de grafite a base poliuretana modificados com SBA-15 na determinação dos antioxidantes BHA e TBHQ em biodiesel(Universidade Federal do Maranhão, 2017-09-05) OLIVEIRA, Danielle Cristina Vasconcelos de; MARQUES, Edmar Pereira; 032.416.453-04; http://lattes.cnpq.br/2468528554511482Due to the importance of the antioxidants to guarantee the quality of the biodiesel, by the parameters of its oxidative stability, analytical methodologies have been developed to quantitatively evaluate the antioxidants present in the biodiesel matrices. In this work SBA-15 and Ni- SBA-15 (nickel incorporated in the SBA-15) were synthesized by the hydrothermal method and characterized, being used as modifier (2.5%) in polyurethane graphite based electrochemical sensors to compare their Performance in determining the antioxidants BHA (3-tert-butyl-4-hydroxyanisole) and TBHQ (tert-butylhydroquinone). Among the sensors used, the GPU electrode modified with SBA-15 was the one that presented the best response in the determination of the antioxidants in the preliminary tests, being then applied in the determination of the antioxidants in the biodiesel sample, using the technique of Differential Pulse Voltammetry (DPV ), Using BR as buffer pH = 2 as the electrolyte. The proposed method presented a linear response in the antioxidant determinations (0.993, for TBHQ determinations and 0.977 for BHA determinations), good results for the limit of detection (LOD BHA = 1, (2.03 for determinations of TBHQ and 2.13 for determinations of BHA) and accuracy (102.5% for determinations of TBHQ and 98, 97% for BHA determinations).Item Detecção fotoeletroanalítica de adrenalina baseada em DNA e nanopartículas de TiO2 sensibilizadas com Bis (Etilenoditio) tetratiofulvaleno explorando luz de led(Universidade Federal do Maranhão, 2017-09-11) SANTOS, Thiago Augusto Dias; DAMOS, Flávio Santos; 846.255.703-87; http://lattes.cnpq.br/0915687070195770; ARAUJO, Adriana Barbosa; http://lattes.cnpq.br/1008844766307732; SANTANA, Sirlane Aparecida Abreu; http://lattes.cnpq.br/1052349578152491A photoelectroanalytical sensor was developed, based on deoxyribonucleic acid (DNA) and anatase titanium dioxide (TiO2) nanoparticles sensitized with bis(ethylenedithio)tetrathiofulvalene (BEDT-TTF) for determination of the adrenaline, also denominated as epinephrine. The photosensor composite developed was denominated as BEDT-TTF/DNA/TiO2/ITO and shows a high photocurrent for the adrenaline under light emitting diode (LED) irradiation in comparison to each component of the composite material. Under optimized conditions, the BEDTTTF/DNA/TiO2/ITO sensor shows a linear response range from 10 nmol L-1 up to 100 μmol L-1 with a sensitivity of 8,1 nA L μmol-1 and limit of detection of 1 nmol L-1 for the adrenaline. The photoelectrochemical sensor showed high photocurrent to adrenaline in comparison to photocurrent response to ascorbic acid and uric acid. The BEDT-TTF/DNA/TiO2/ITO photoelectrochemical sensor was successfully applied to urine samples, with recovery values between 96 and 106%.Item Nanocompósitos argila-ioneno aplicados à remoção de petróleo e seus derivados em meio aquoso(Universidade Federal do Maranhão, 2017-07-27) RODRIGUES, Marta Venancia França; COSTA FILHO, Arão Pereira da; 291.814.453-34; http://lattes.cnpq.br/3819822912193806; SANTANA, Sirlane Aparecida Abreu; 292.469.730-49; http://lattes.cnpq.br/1052349578152491; CAVALCANTE, Kiany Sirley Brandão; http://lattes.cnpq.br/3810732989135120; DAMOS, Flávio Santos; http://lattes.cnpq.br/0915687070195770This work aimed to prepare a material, from the intercalation of a Maranhense clay with a polymer, able to adsorb oil derivatives in aqueous media. The polymer was synthesized from a copolymerization reaction between a tertiary amine and an organic halide, known as Ionene, which was characterized by hydrogen nuclear magnetic resonance (1 H-NMR). The preparation of the clay-ionene adsorbent occurred by the exchange of the interlamellar inorganic cations by the organic cations of the polymer, after the clay in natura receive acid and alkaline treatment. X-ray Diffraction (XRD), Infrared Spectroscopy (FTIR), Surface Area, Thermogravimetry (TG) and Foster Swelling performed the characterization of the new material. The results showed that the cation exchange process occurred, confirmed by the increase of the basal distance (d001) observed in the XRD and by the appearance of the characteristic bands of the organic cations detected by the infrared spectra. The Foster swelling results show that the nanocomposite has higher interaction with organic solvents. In the adsorption tests the organophilic clays, as expected, presented higher efficiency in relation to the in natura material, with removal rate of approximately 90%. The kinetic modeling studies showed that the adsorption is of pseudo second order, indicating that the process is chemical.Item Um novo e seletivo sensor à base de CuTSPc e óxido de grafeno reduzido para a determinação individual e simultânea dos antioxidantes BHA e TBHQ em amostras de biodiesel(Universidade Federal do Maranhão, 2016-07-29) Carvalho, Rita Maria de Sousa; LUZ, Rita de Cássia Silva; 812.848.293-91A novel and selective electrochemical sensor for the determination of the butylated hydroxyanisole (BHA) and tert-butylhydroquinone (TBHQ) antioxidants employing the differential pulse voltammetry (DPV) was developed. In this sense, a glassy carbon electrode (GCE) modified with a copper tetrasulfonated phthatocyanine (CuTSPc) adsorbed on reduced graphene oxide (rGO) showed excellent response for the TBHQ and BHA oxidation with a decrease in the overpotentials about 130mV vs Ag/AgCl and anodic peak currents about 4 times higher than the observed responsesat an electrode unmodified. The increase of the oxidation reaction rates for TBHQ and BHA was attributed to the efficient electron transfer between the studied species and the immobilized materials on surface of the GCE.The materials rGO, CuTSPc and rGO/CuTSPc were characterized by Fourier transform infrared spectroscopy (FTIR) and the analytical response of the sensor for the analytes was studied by cyclic voltammetry (CV) and linear scan voltammetry (LSV) techniques. After optimization of the experimental parameters, the analytical curves for determination of BHA and TBHQ by DPV technique demonstrated an excellent linear response from 0.1 to 500µmol L-1 with detection limit of 0.045 µmol L-1 for TBHQ and 0.036 µmol L-1 for BHA. Finally, the proposed method was successfully applied in the simultaneous determination of BHA and TBHQ in six biodiesel samples, and the results obtained were found to be similar to those obtained using the HPLC method with agreement at 95 % confidence level. The addition and recovery studies have shown that the proposed method has good accuracy with recovery values between 99.5 and 100.5 % forTBHQ and 99.1 and 100.2 for BHA.Item Redução do Oxigênio Molecular por [Fe(Bipy)3]/C: influência do suporte e do tratamento térmico na atividade catalítica.(Universidade Federal do Maranhão, 2011-01-25) Rêgo, Ulisses Alves do; BEZERRA, Cícero Wellington Brito; 311.559.103-97This work consisted in the preparation and study of catalytic activity for reduction of molecular oxygen (ROM) based on head-treated coordination compounds with nitrogenated ligands, impregnated on carbon nanosupports (nanotube - NTC, and nanoparticles - Vulcan). The following ions complexes [Fe(bipy)3]2+ and [Fe(TPTZ)2]2+ (2,2 '-bipyridine and 2 ,4,6-tris (2-pyridyl) -1,3,5-triazine) were synthesized and characterized in solution (electron spectroscopy in the region UV-vis, cyclic voltammetry). The following materials were prepared C1: Fe(10%)-Bipy/NTC; C2: Fe(5%) -Bipy/NTC; C3: Fe(5%)-Bipy/Vulcan and C4: Fe(5%)-TPTZ/Vulcan. The comparison between C1 and C2, and between C2 and C3 materials, showed, respectively, the effect of metal loading and the nature of the carbon support on their catalytic efficiency. The comparison among all and C4 (already reported in the literature) allowed the verification of experimental methodology employed. The effect of temperature on the electrocatalytic performance was observed for C1. The following pyrolysis temperatures were used: 600-1000 oC. The results showed that metal loading and the nature of the support influence the catalytic ability of the materials. The best pyrolysis temperature observed to generate active sites in C1 for the ROM was at 800 oC. All materials were treated at this temperature, and the efficiency order observed was: C4 (Fe (5%) -TPTZ/Vulcan) >> C1 (Fe(10%)-Bipy/NTC) > C2 (Fe(5%)-Bipy/NTC) > C3 (Fe (5%) -Bipy/Vulcan). For not heat treated materials, the activity order observed was: C3 (Fe(5%)-Bipy/Vulcan) C4 (Fe (5%)-TPTZ/Vulcan) > C1 (Fe (10%)-bipy/NTC) > C2 (Fe (5%) -Bipy/NTC). C2 and C3 catalysts showed a tendency to reduce the molecular oxygen according to 2e- mechanism, while C1 and C4 materials by 4e- mechanism. For some reason, the TPTZ ligand favored the generation of catalytic sites more efficient than Bipy in these materials.Item SENSOR ELETROQUÍMICO À BASE DE NiAlPO-5 PARA DETERMINAÇÃO DE Cu2+ EM ETANOL COMBUSTÍVEL(Universidade Federal do Maranhão, 2017-03-06) CASTRO, Aleff Cruz de; MARQUES, Aldaléa Lopes Brandes; 076.486.263-49Zeolites are microporous inorganic materials with a variety of applications in several areas of science and engineering. Their physical and chemical properties are attributed to the large internal surface area, and the chemical and hydrothermal stability, which are induced by the existence of well defined channels and/or cavities. These structural characteristics promote the use of zeolites as catalysts, molecular sieves, ion exchangers and, more recently, as electrochemical sensors. Taking in consideration these premises, this work describes the development of an electrochemical sensor obtained from the modification of the polyurethane graphite composite electrode with NiAlPO-5, a nickel-modified AFI aluminophosphate, and its application for determination of Cu2+ in ethanol biofuel. The synthesis of the aluminophosphates were conducted by the hydrothermal method and the obtained materials were characterized by X-ray diffraction, scanning electron microscopy, 31P nuclear magnetic resonance and UV-Vis and infrared spectroscopy. After synthesis and characterization, materials were used as modifiers (10%) in GPU electrodes in order to compare the performance of the unmodified and modified electrodes by Square Wave Anodic Stripping Voltammetry. The results showed that the incorporation of Ni to the material structure promotes an improvement in the electrical properties and analytical properties of the electrode. The analytical response of the sensor in the copper ion determination showed that the NiAlPO-5 electrode is more sensitive in terms of peak current than the electrolyte based on AlPO-5 only. The best response was obtained with the Ni/Al ratio of 0.5 on the NiAlPO-5 sensor. The experimental conditions of potential and deposition time, pulse amplitude, step potential, frequency and pH were optimized in an electrochemical cell containing 2 mL of ethanol, 8 mL of HCl 0.1 mol L-1 and Cu2+ concentration of 2.5×10-7 mol L-1. GPU/NiAlPO-5 modified sensor was then evaluated for electroanalytical determination of Cu2+ in ethanol biofuel samples presenting a linear response for Cu2+. Good results were obtained for the limit of detection (9.44×10-9 mol L-1), accuracy (recovery of 115%) and precision (RSD of 5.92%).Item DESENVOLVIMENTO E APLICAÇÃO DE METODOLOGIA ANALÍTICA (CLAE/FL) PARA DETERMINAÇÃO DE FLUOROQUINOLONAS EM SEDIMENTO ESTUARINO DA ILHA DO MARANHÃO(Universidade Federal do Maranhão, 2014-12-19) Neves, Mônica Araujo das; Marques, Edmar Pereira; CPF:03241645304; http://lattes.cnpq.br/2468528554511482; SILVA, Gilmar Silvério da; CPF:10011120100; http://lattes.cnpq.br/6983165980341102Drugs in the planet have increased during last decades. Such compounds can cause adverse impact on ecosystems. Soon, more effective analytical methods are essential for the study of new pollutants, especially in magazines whose headquarters are very complex as mangrove sediments. Therefore, this study aimed to improve an analytical method to assess the occurrence of fluoroquinolone antibiotics, ciprofloxacin (CIP), levofloxacin (LEV) and norfloxacin (NOR), in sediment samples from the Paciência river located on the Maranhão island using the technique of ultrasound-assisted extraction, extraction phase solid and liquid chromatography (HPLC/FD). According to the study, the method was linear (r²> 0.99), recovery ranging from 73.73 to 88.85%, precise (RSD <20%), selective and sensitive (detection limit for CIP, LEV and NOR 9.32; 17.78 and 4.42 µg.kgˉ¹, respectively, and limit of quantitation of 20 µg.kgˉ¹ for all three drugs) for quantification of fluoroquinolones in estuarine sediments. Other relevant aspects of the method developed in this work were the simplicity, low cost and absence of interfering to a very complex environmental matrix as are the mangrove sediments. When evaluating the sediment at various points of the river there was contamination at three points by CIP ranging from 56.55 to 70.45 µg.kgˉ¹ These results are similar to those found around the planet to polluted regions and they are of concern due to the effects of these antibiotics in the ecosystem.Item DETERMINAÇÃO ESPECTROFOTOMÉTRICA DE DICLOFENACO DE SÓDIO EM FORMULAÇÃO FARMACÊUTICA EMPREGANDO O CONCEITO DE FIA-MULTICOMUTAÇÃO(Universidade Federal do Maranhão, 2014-03-28) Gomes, Paulo Roberto Barros; FERNANDES, Ridvan Nunes; CPF:00062700300; http://lattes.cnpq.br/9020022655425615; Silva, Gilmar Silvério da; CPF:10011120100; http://lattes.cnpq.br/6983165980341102International and national bodies require the development of analytical methods that are rapid, inexpensive and accurate for the determination of drugs. One way to meet these requirements a method of flow injection analysis employing multicommutation and spectrophotometric detection was used. In this paper an automated system was developed to determine diclofenac sodium in injectables. The reaction is based on the oxidation of diclofenac sodium with potassium permanganate in acid medium be-ing monitored at 465 nm this. The calibration curve was linear over the concentration range of 20-80 mg Lˉ¹ with a detection limit of 0.1 mg Lˉ¹ standard deviation of 0.9% (n = 20) and Sample Rate 80 samples per hour. The proposed method was applied successfully in three injectable solutions and the samples were compared with the official method and other automated methods employing the same reaction.Item COMPARAÇÃO DE SENSORES ELETROQUÍMICOS PARA DETERMINAÇÃO DE ENXOFRE EM BIODIESEL(Universidade Federal do Maranhão, 2013-06-06) Costa, Helmara Diniz; MARQUES, Edmar Pereira; CPF:03241645304; http://lattes.cnpq.br/2468528554511482; Santana, Sirlane Aparecida Abreu; CPF:29246970349; http://lattes.cnpq.br/1052349578152491Due to the implementation of more restricted environmental regulation laws, the control of pollution agent such as sulfur compounds has provides the development of new analytic methodologies for its quantification on different matrices, including biodiesel fuel. Thus, this work aims to compare three different sensors - film bismuth and mercury film on the surface of a glassy carbon electrode and solid silver amalgam (dental) - for the determination of sulfur in biodiesel, by means of stripping voltammetric cathodic square wave mode (VRC/SW) as supporting electrolyte with a solution of sodium acetate (1,4 mol.Lˉ¹) and acetic acid (0.33 mol.Lˉ¹) in metanol/2-propanol. In general, the mercury film electrode (MFE) has presented the best electrochemical behavior to the definition of peak reduction, being then selected as standard electrode to the measurements. The sulfur quantization on biodiesel samples was performed by adding 70 μL of soybean biodiesel and tallow fatty with TMAH, adding later, aliquots of standard sulfur. The method showed good linearity (0.998), suggesting an average sulfur concentration of 6,870x10ˉ7 (± 6,857x10ˉ⁸) mol.Lˉ¹, within a confidence interval of 95%, to a limit of detection 3,294x10ˉ¹º mol.Lˉ¹ and quantification limit of 1,098x10ˉ9 mol.Lˉ¹. Besides, for the untreated sample, the experimental has provided a LD of 6,54 x 10ˉ9 mol.Lˉ¹. Finally the proposed method has been compared with the results of a collaborative study (ANP 01/2012) of the same sample using the Teste-t de Student, verifying that the proposed method and official methods (EN ISO 20846, EN ISO 20884) are statistically equivalent to a confidence level of 95%, thereby demonstrating the feasibility of the method.