DISSERTAÇÃO DE MESTRADO - PROGRAMA DE PÓS-GRADUAÇÃO EM QUIMICA

URI Permanente para esta coleçãohttps://tedebc-teste.ufma.br/handle/tede/881

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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/0310068697989712
This 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.
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/8536193616269377
A 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.
AVALIAÇÃO POR ESPECTROSCOPIA DE IMPEDÂNCIA ELETROQUÍMICA DO EFEITO CORROSIVO DE BIODIESEL PURO E MISTURAS EM ALUMÍNIO
(Universidade Federal do Maranhão, 2013-06-07) Cordeiro, Cristiane Italiano; RODRIGUES, José Roberto Pereira; CPF:37536001304; http://lattes.cnpq.br/6186580867262823; Maciel, Adeilton Pereira; CPF:92935427491
The use of biodiesel as fuel has presented a great potential in the world, both for its contribution to the environment as well as for being a fuel derived from renewable sources. However, this fuel is causing serious problems of corrosion metallic in materials used in diesel engines, transport systems and storage. In this sense, the present work aims, evaluating the corrosive effect of biodiesel and mixtures in aluminum by means of electrochemical techniques, as the open circuit potential and impedance electrochemical spectroscopy. For such, were used aluminum blades immersed in samples of B100 biodiesel and mixtures of B5 and B4, was also used microemulsion samples for obtaining better answers in the electrochemical trials. The surface of the metalic material was evaluated, after immersion trials, by visualization the optical microscope, in order to identify the effect caused by corrosion. The results obtained for trials showed that aluminum presented a good corrosion resistance in contact with the fuel samples, as well as in samples microemulsion.
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 Cássia
Textile 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).
CASCA DE ARROZ COMO ADSORVENTE PARA ÍONS DE METAIS PESADOS: Caracterização e modificação química
(Universidade Federal do Maranhão, 2009-01-09) Penha, Rosiane Silva; BEZERRA, Cícero Wellington Brito; CPF:31155910397; http://lattes.cnpq.br/1474300723265204; Ramos, Antonio Carlos da Silva; CPF:70434212415
Adsorption of some metal ions (Co2+, Ni2+, Cu2+ e Zn2+) from aqueous solutions (pH 5.0) onto in nature rice husk (0.088 <  < 0.177 mm) was investigated. All experiments were conducted by the batch adsorption techniques at room temperature (28  1°C) and under constant stirring. The adsorption amounts were determined using atomic absorption spectroscopy. The Adsorption data were studied using two well-known adsorption models: Langmuir and Freundlich. The results showed that the metal ions uptake processes mediated by rice husks were fitted Freundlich isotherm model, suggesting that all adsorptions are governed by weak electrostatic interactions. According to the equilibrium studies, the selectivity sequence can be given as: Ni2+ (0.08 mmol g-1) < Co2+ (0.16 mmol g-1) < Zn2+ (0.40 mmol g-1) < Cu2+ (0.89 mmol g-1). This result showed that natural rice rusk holds good potential to remove such metal ions from wastewater. The effect of chemical pretreatment of rice husk on adsorption was also investigated. In nature rice husk (IN) was pretreated with phosphoric acid (AF); phosphoric acid and urea (AFU) and sodium metaperiodate (MP). AFU was the best adsorbent for all metal ions investigated [Ni2+ (0,96 mmol g-1) < Cu2+ (1,20 mmol g-1) < Co2+ (1,59 mmol g-1) < Zn2+(1,80 mmol g-1)]. In addition, in nature rice husk was characterized by chemical-bromatological analyses (humidity, ash, protein, carbohydrate, starch, lipid and fibers), scanning electron microscopy, solid-state 13C NMR and specific BET surface area. Some properties of in nature and pretreated samples were studied by infrared spectroscopy, thermogravimetric analysis, X-ray diffractometry, and elemental analyses. The results showed only marginal changes among them.
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/1052349578152491
Due 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.
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/0915687070195770
The 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.
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/2468528554511482
Due 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).
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 Almeida
This 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.
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/1008844766307732
This 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.
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/6983165980341102
Drugs 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.
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/1052349578152491
A 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%.
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/6983165980341102
International 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.
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/6219897465386798
Substances 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.
DISTRIBUIÇÃO E FRACIONAMENTO DE FÓSFORO EM SEDIMENTOS DE MANGUEZAIS DO ESTUÁRIO DO RIO TIBIRI NA ILHA DO MARANHÂO, REGIÃO AMAZÔNICA
(Universidade Federal do Maranhão, 2013-10-25) Jesus, Edson Tobias de; SILVA, Gilmar Silvério da; CPF:10011120100; http://lattes.cnpq.br/6983165980341102; Mouchrek Filho, Victor Elias; CPF:70434212415; http://lattes.cnpq.br/2381183158978639
In order to assess the environmental impact and the behavior of phosphorus in the sediments of mangrove Tibiri River on the Maranhão island, five phosphorus fractions were determined (TP, IP, OP, AP) and NAIP in mangrove sediment, through sequential extraction according to the protocol of the European Commission (SMT - standards, measurements and testing Programme). Concentrations of the majority metals were also determined (Ca , Al , Mg , Fe and Mn) by inductively coupled plasma atomic with optic emission spectrometry (ICPAES) in the same extracts of cited above, moreover, mineralogical analysis of the mangrove sediment was made by X-ray diffraction. Sediments form Tibiri River showed phosphorus levels in the order of 341.44 mg.kg-1, characterized as an estuary with inexpressive impact of anthropogenic activities. Most phosphorus is found in the non-apatite inorganic fraction, (NAIP), mean 70%. The inorganic fraction of phosphorus, such as apatite mineral (PA) remained at 29%. Rio Tibiri was classified as unpolluted (PT < 500 mg kg-1), although most phosphorus is found as labile (mean 73.68%). Among the majority metals, Ca stood out by its association with the apatite fraction (AP), Corroboratig the presence of this mineral in the sediment. The main clay minerals found were kaolinite, montmorillonite , illite and quartz.
ESTABELECIMENTO DE CONDIÇÕES ANALÍTICAS PARA DETERMINAÇÃO DE HORMÔNIOS ESTRÓGENOS EM ÁGUA POTÁVEL DISTRIBUÍDA NA CIDADE DE SÃO LUÍS-MA
(Universidade Federal do Maranhão, 2009-04-28) Verbinnen, Raphael Teixeira; NUNES, Gilvanda Silva; CPF:27928853353; http://lattes.cnpq.br/5833210771020427
Given the humanity perception of necessity to preserve the environment and the incessant search for sustainable development, today the preservation of natural water sources is by far one of the most worrying factors for the preservation of life. Besides the most common aquatics pollutants, also there is one called emerging pollutants, which in recent decades have been detected due the technological advances. These involve mainly the organic micropollutants, which present the endocrine disrupters (ED's) main group. Among the ED's, the natural and synthetic sex steroids hormones have significant importance because their daily use in medicine, in the replacement therapy and contraceptive methods, which has contributed to the continuous release in domestic sewage. There are several consequences of this effect, including fertility declining, occurrence of various cancers and disorders in the development and homeostasis of organisms. The domestic and industrial sewage and leaching from agricultural fields fertilized with sludge from sewage treatment plants (STP's) are the main sources of contamination. This study allowed the chromatographic separation of the hormones estriol (E3), 17 β-estradiol (E2), estrone (E1) and 17 α-ethynylestradiol (EE2) in relatively short duration (16,5 minutes), using the acetonitrile:water (ACN: H2O) mixture as mobile phase in gradient mode, constant flow of 1 mL min-1, injection volume of 20 μL, λ = 280 nm and temperature of 27 ºC. The method was developed in two laboratories, involving different instruments. Four procedures and two adsorbents (C18 e OPT) of SPE were tested. The sample preparation method, including dechlorination and the SPE procedure with C18 cartridge, resulted in the recovery values within the acceptable limit. The developed method was validated according to guidelines of the ANVISA`s Guide for Validation, and bioanalytical methods was adapted for this study. The method was then applied in the analysis of the natural (17β-estradiol, estrone and estriol) and the synthetic (17α-ethinylestradiol) hormone in drinking water from the city of São Luís Peaks were not identified for the substances studied, probably substances concentrations below the limits of detection and quantification of the method were found.
ESTUDO DA COMPOSIÇÃO E APLICAÇÃO DO ÓLEO ESSENCIAL DE Origanum vulgare L. COMO AGENTE ANTIMICROBIANO EM SURURU (Mytella falcata).
(Universidade Federal do Maranhão, 2013-11-29) Liston, Mariane da Silva; MOUCHREK FILHO, Victor Elias; CPF:70434212415; http://lattes.cnpq.br/2381183158978639; Nascimento, Adenilde Ribeiro; CPF:10455825300
Essential oils (OEs) are natural plant extracts and many of them are active as antimicrobials. Origanum vulgare L. (oregano) essential oil (OEO) has a promising application field as a food preservative. Several in vitro and application studies has been carried to evaluate the activity of OEs as antimicrobials in foods, but are not found in the literature survey data application in mussels. In this study we evaluated the chemical composition and the antibacterial effect of OEO in fresh chilled mussels from Mytella falcata species. The chemical constituents of the studied OE were identified by gas chromatography-mass spectrometry and for activity we analyzed the count of Escherichia coli and aerobic mesophilic bacteria, total volatile bases and pH. The addition of OEO at 1.4% resulted in complete inhibition of E. coli inoculated, reduced growth aerobic plate count bacteria and inhibit the process of deterioration. The activity of the OEO is attributed mainly to its major component, carvacrol, which has recognized antibacterial activity. The results indicate that the OEO can be applied to support of the extension of shelf life and safety of fresh mussels.
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 de
This 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.
ESTUDO DAS REAÇÕES DE OXIDAÇÃO DE METANOL E ETANOL SOBRE CATALISADORES BI E TRIMETÁLICOS ATRAVÉS DE TÉCNICAS DE VOLTAMETRIA CÍCLICA E DEMS
(Universidade Federal do Maranhão, 2006-07-24) Silva, Quésia Guedes da; RODRIGUES, Isaide de Araújo; CPF:17928893304
The interest in the use of methanol and ethanol as fuels in a fuel cell is justified by the search for new energy conversers, more efficient and less polluters. This work presents the study of the oxidation reaction these alcohols on catalysts obtained by potentiostatic deposition of Pt or codeposition of PtRu, PtRuSn e PtSn using as subtract a Teflon membrane GORE-TEK with sputtering of 600nm of gold and a geometric area of 1,11cm2. The reference electrode used was the reversible of hydrogen, as an opposite electrode there was a platinum sheet. The experiments were made using the combination of cyclic voltammetry and on line mass spectrometry, called differential electrochemical mass spectrometry (DEMS) The electroposits were examined using X-ray energy dispersive analysis (EDAX) and scanning electron microscopy (SEM) The electrochemistry results have shown that Pt-Ru catalyst presented better catalitic activity to methanol oxidation in lower potentials, showing the following sequence to catalitic activity: PtRu > PtRuSn @ PtSn > Pt. The mass spectrometry data have shown similar results with better performance to PtRu electrode in the CO2 (m/z = 44) production. In the case of the ethanol oxidation the electrochemistry data show that the catalyst Pt-Sn and Pt-Ru- Sn were the most active in lower potentials. The mass spectrometry results have shown that, when compared with others, the PtSn electrode presents greater activity both in the CO2 production as well as in the acetaldehyde s.
ESTUDO QUÍMICO E ATIVIDADE ANTIFÚNGICA DO ÓLEO ESSENCIAL DOS FRUTOS DA Pimenta dioica Lindl.
(Universidade Federal do Maranhão, 2011-06-10) B. Júnior, Francisco Reivilandio da S.; MOUCHREK FILHO, Victor Elias; CPF:70434212415; http://lattes.cnpq.br/2381183158978639
Jamaican pepper, Pimenta dioica Lindl, is a species belonging to the family of Myrtacea, measuring 6m to 15m high, very aromatic in all its parts. It is originally from Central America and West India and with great economic importance in the market of essential oils. The extraction of the essential oil of Pimenta dioica L seeds was carried out by using the method of hydrodistillation known as Cleverger system. It was extracted from a maximum volume of oil in the period of four hours with a yield of 2.8% m/m. The UV spectrophotometric techniques, mass spectrometry and gas chromatography, as well as the physical constants, density, color and appearance were used to identify the compound eugenol and other constituents of the essential oil of P. dioica L. Through the technique of external standard and standard addition it was quantified with a eugenol percentage of 76.98%, forming the major component. The essential oil of Pimenta dioica L was applied to the phyto pathogenic fungi species Fusarium oxysporum f. sp. lycopersici, Fusarium oxysporum f. sp. passiflorae, Fusarium subglutinans f. sp ananas., Fusarium oxysporum f. sp. vasinfectum and Fusarium oxysporum f. sp. cubense resulting in a total inhibition of mycelial growth of all species tested for a period of ten days of evaluation.

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