Preconcentration and determination of metal ions from fuel ethanol with a new 2,2'-dipyridylamine bonded silica

A silica surface chemically modified with [3-(2,2'-dipyridylamine) propyl] groups was prepared, characterized, and evaluated for its metal ion preconcentration in fuel ethanol. To our knowledge, we are the first authors who have reported the present modification on silica gel surface. The material was characterized using infrared spectra, scanning electronic microscopy, and 13C and 29Si solid-state NMR spectra. Batch and column experiments were conducted to investigate for metal ion removal from fuel ethanol. The results showed that the Langmuir model describes the sorption equilibrium data of the metal ions in a satisfactory way. From the Langmuir isotherms, the following maximum adsorption capacities (in mmolg -1) were determined: 1.81 for Fe(III), 1.75 for Cr(III), 1.30 for Cu(II), 1.25 for Co(II), 1.15 for Pb(II), 0.95 for Ni(II), and 0.87 for Zn(II). Thermodynamic functions, the change of free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) showed that the adsorption of metal ions onto Si-Pr-DPA was feasible, spontaneous, and endothermic. The sorption-desorption of the metal ions made possible the development of a preconcentration and quantification method of metal ions in fuel ethanol. © 2012 Elsevier Inc.

Adsorption of heavy metal ions and epoxidation catalysis using a new polyhedral oligomeric silsesquioxane

The objective of this research was the preparation of a silsesquioxane functionalized with eight chloropropyl chains (T8-PrCl) and of a new derivative functionalized with a pendant linear chain (2-amino-1,3,4-thiadiazole - ATD; T8-Pr-ATD). The two nanostructured materials were characterized by 13C and 29Si NMR, FTIR and elemental analysis. The new nanostructured material, octakis[3-(2-amino-1,3,4-thiadiazole)propyl] octasilsesquioxane (T8-Pr-ATD), was tested as a ligand for transition-metal ions with a special attention to adsorption isotherms. The adsorption was performed using a batchwise process and the organofunctionalized surface showed the ability to adsorb the metal ions Cu (II), Co (II), and Ni (II) from water and ethanol. The adsorption isotherms were fitted by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) model. The kinetics of adsorption of metals were performed using three models such as pseudo-first order, pseudo-second order and Elovich. The Langmuir and Elovich models were the most appropriate to describe the adsorption and kinetic data, respectively. Furthermore, the T8-Pr-ATD was successfully applied to the analysis of environmental samples (river and sea water). Subsequently, a new nanomaterial was prepared by functionalization of the T8-Pr-ATD with a Mo (II) organometallic complex (T8-Pr-ATD-Mo). Only a few works in the literature have reported this type of substitution, and none dealt with ATD and Mo (II) complexes. The new Mo-silsesquioxane organometallic nanomaterial was tested as precursor in the epoxidation of cyclooctene and styrene. © 2012 Elsevier B.V.

Sulfonation and anticoagulant activity of fungal exocellular β-(1→6)-d-glucan (lasiodiplodan)

An exocellular β-(1→6)-d-glucan (lasiodiplodan) produced by a strain of Lasiodiplodia theobromae (MMLR) grown on sucrose was derivatized by sulfonation to promote anticoagulant activity. The structural features of the sulfonated β-(1→6)-d-glucan were investigated by UV-vis, FT-IR and 13C NMR spectroscopy, and the anticoagulant activity was investigated by the classical coagulation assays APTT, PT and TT using heparin as standard. The content of sulfur and degree of substitution of the sulfonated glucan was 11.73% and 0.95, respectively. UV spectroscopy showed a band at 261 nm due to the unsaturated bond formed in the sulfonation reaction. Results of FT-IR and 13C NMR indicated that sulfonyl groups were inserted on the polysaccharide. The sulfonated β-(1→6)-d-glucan presented anticoagulant activity as demonstrated by the increase in dose dependence of APTT and TT, and these actions most likely occurred because of the inserted sulfonate groups on the polysaccharide. The lasiodiplodan did not inhibit the coagulation tests. © 2012 Elsevier Ltd.

Experimental NMR and MS study of benzoylguanidines. Investigation of E/Z isomerism

Molecules containing the guanidinic nuclei possess several pharmacological applications, and knowing the preferred isomers of a potential drug is important to understand the way it operates pharmacologically. Benzoylguanidines were synthesized in satisfactory to good yields and characterized by NMR, Electrospray Ionization Mass Spectrometry (ESI-MS) and Fourrier Transform InfraRed Spectroscopy techniques (FTIR). E/Z isomerism of the guanidines was studied and confirmed by NMR analysis in solution (1H-13C Heteronuclear Single Quantum Coherence (HSQC) and Heteronuclear Multiple-Bond Correlation (HMBC), 1H-15N HMBC, 1H- 1H Correlation Spectroscopy (COSY) and Nuclear Overhauser Effect Spectroscopy (NOESY) experiments) at low temperatures. Compounds with p-Cl and p-Br aniline moiety exist mainly as Z isomer with a small proportion of E isomer, whereas compounds with p-NO2 moiety showed a decrease in proportion of isomer Z. The results are important for the application of these molecules as enzymatic inhibitors. Copyright © 2013 John Wiley & Sons, Ltd.

Luminescent properties of hybrid materials prepared by the polymeric precursor method

Rare earth complexes (RE) can be incorporated in silica matrixes, originating organic/inorganic hybrid materials with good thermal stability and high rare earth emission lines. In this work, the hybrid material was obtained by the polymeric precursor method and ultrasonic dispersed with spherical silica particles prepared by the Stöber Method. The Raman spectra indicated that the Eu3+ ions are involved in a polymeric structure formed as consequence of the chelation and polyesterification reactions of this ion with citric acid and ethylene glycol. After the ultrasonic stirring, 2-hydroxynicotinic ligand will also compose this polymeric rigid structure. The TGA/DTA analysis showed that this polymeric material was thermal decomposed at 300 °C. Moreover, this process allows the chelating process of the 2-hydroxynicotinic acid ligand to the Eu3+ ions. The 29Si NMR showed that the ultrasonic dispersion of the reactants was not able to promote the functionalization of the silica particles with the 2-hydroxynicotinic acid ligand. Moreover, heat treatment promotes the [Eu(HnicO2)3] complex particles incorporation into silica pores. At this temperature, the TGA curve showed that only the thermal degradation of ethylene glycol and citric acid used during the experimental procedure occurs. The silica and hybrid materials are composed by spherical and aggregated particles with particle size of approximately 450 nm, which can be influenced by the heat treatment. These materials also present an absorption band located at 337 nm. The photoluminescent study showed that when the hybrid samples were excited at 337 nm wavelength, the ligand absorbs the excitation light. Part of this energy is transferred to the Eu3+ ion, which main emission, 5D0→ 7F2, is observed in the emission spectrum at 612 nm. As the heating temperature increases to 300 C, the energy transfer is more favorable. The lifetime values showed that the Eu3+ emission is enhanced due to the energy transfer process in the powders. © 2013 Elsevier B.V. All rights reserved.

Síntese de sucroésteres derivados de ácidos piridínicos (ácido nicotínico, isonicotínico e pícolínico) e avaliação de suas atividades antimicrobianas

Pós-graduação em Engenharia e Ciência de Alimentos - IBILCE

Estudo e otimização da produção da dextranasacarase e caracterização da dextrana produzida por Leuconostoc mesenteroides FT045B

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Substâncias húmicas aquáticas: caracterização e interação com íons crômio e proposta de um indicador de matéria orgânica lábil

Pós-graduação em Química - IBILCE

Caracterização físico-química e avaliação toxicológica preliminar do copolímero sulfato de condroitina-co-N-isopropilacrilamida para uso farmacêutico

A Indústria Farmacêutica utiliza polímeros em forma de nanopartículas em formulações de liberação controlada e vetorizada por possuírem baixo custo em relação a demais métodos de preparações de formas farmacêuticas, aparentemente não serem reconhecidos pelo sistema de defesa do organismo, proporcionar melhora da eficácia, diminuição da toxicidade e da dose de fármaco administrado. O sulfato de condroitina-co-Nisopropilacrilamida (SCM + NIPAAm) é um copolímero proposto para este fim, a partir da reação de um polímero sintético, o poli N-isopropilacrilamida (PNIPAAm), com características termossensíveis, com um natural, o Sulfato de Condroitina (SC), com características bioadesivas. Assim, a copolimerização pode ser capaz de somar estas propriedades e aperfeiçoar o seu uso como um veículo para liberação controlada. Este trabalho objetivou, portanto, realizar a caracterização fisico-quimica das partículas de sulfato de condroitina e Nisopropilacrilamida e do copolímero SCM+NIPAAm (2,5 % e 5%) e do SCM+PNIPAAm 2,5% e uma avaliação toxicológica parcial de um destes copolímeros que apresentar as melhores propriedades de um eficiente carreador de fármacos, selecionado a partir dos ensaios de caracterização físico-química. Para determinar a estrutura química dos sistemas particulados e analisar os seus componentes químicos, foi realizada a Espectroscopia de Ressonância Magnética Nuclear (RMN) e Espectroscopia do Infravermelho com Transformada de Fourrier (FTIR); Para analisar a morfologia das partículas, foi usado a Microscopia Eletrônica de Varredura (MEV); A Termogravimetria/ Termogravimetria Derivada e Análise Térmica Diferencial (TG/DTG) foi usada para avaliar o comportamento térmico dos sistemas particulados, bem como auxiliar na análise de Cinética de Degradação (CD, método de Flynn-Wall-Ozawa); Foi ainda realizado a técnica de degradação in vitro e a determinação carga superficial e tamanho de partículas (análise do Potencial Zeta, PZ). Para avaliar a toxicidade, foi realizado o bioensaio em microcrustáceo Artemia salina (24 e 48 h), viabilidade celular (citotoxicidade) em células PC-12 (método do MTT) e também a toxicidade aguda oral em camundongos. As análises de RMN, FTIR e MEV demonstraram semelhança quanto ao aspecto estrutural e morfológico entre os copolímeros estudados. As análises de TG demonstraram que o SCM+NIPAAm 5% apresentou maior estabilidade térmica em relação aos demais copolímeros avaliados, uma vez que sua decomposição polimérica ocorre em temperaturas superiores, em torno de 233ºC. O DTA demonstrou valores de temperaturas concordantes com os eventos térmicos de decomposição apresentados pelas curvas das análises TG. Sua estabilidade foi confirmada através da CD e estudo de degradação in vitro, apresentando, respectivamente, Ea > 100 kJ mol^-1 e perda de 48% da sua massa inicial após três meses. Além disso, SCM+NIPAAm 5% apresentou diâmetro de partícula inferior a 200 nm e índice de polidispersão de 0,35, além do PZ > -30mV, caracteristicas de um promissor candidato a carreador de fármacos. Em relação às avaliações toxicológicas, o SCM+NIPAAm 5% não apresentou toxicidade no bioensaio de A. salina (CL₅₀ > 1000) e no modelo celular avaliado, dentro das concentrações e circunstâncias de exposição estudadas. O SCM+NIPAAm 5%, na dose oral de 2000 mg/kg, não apresentou nenhum sinal evidente de toxicidade em camundongos, o que foi corroborado pela ausência de alterações anatomo-histopatológicas. A copolimerização do Sulfato de Condroitina e N-isopropilacrilamida na concentração estudada, dada suas características físico-químicas e toxicológicas preliminares, apresenta propriedades que contribuem para a proposta de um sistema que constitui uma nova forma de liberação controlada, especialmente de fármacos.

Síntese, estrutura e propriedades de complexos de molibdênio, prata e chumbo com ácido 'alfa'-hidroxicarboxílicos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Espécies moleculares e supramoleculares de 'PD'(II)' com ligantes mono, bi e polidentados : caracterização estrutural e atividades biológicas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Síntese, caracterização e estudo da atividade antitumoral de complexos de paládio(II) com ligantes sulfurados e trifenilfosfina

Pós-graduação em Química - IQ

RAMSY: Ratio Analysis of Mass Spectrometry to Improve Compound Identification

The complexity of biological samples poses a major challenge for reliable compound identification in mass spectrometry (MS). The presence of interfering compounds that cause additional peaks in the spectrum can make interpretation and assignment difficult. To overcome this issue, new approaches are needed to reduce complexity and simplify spectral interpretation. Recently, focused on unknown metabolite identification, we presented a new approach, RANSY (ratio analysis of nuclear magnetic resonance spectroscopy; Anal. Chem. 2011, 83, 7616-7623), which extracts the signals related to the same metabolite based on peak intensity ratios. On the basis of this concept, we present the ratio analysis of mass spectrometry (RAMSY) method, which facilitates improved compound identification in complex MS spectra. RAMSY works on the principle that, under a given set of experimental conditions, the abundance/intensity ratios between the mass fragments from the same metabolite are relatively constant. Therefore, the quotients of average peak ratios and their standard deviations, generated using a small set of MS spectra from the same ion chromatogram, efficiently allow the statistical recovery of the metabolite peaks and facilitate reliable identification. RAMSY was applied to both gas chromatography/MS and liquid chromatography tandem MS (LC-MS/MS) data to demonstrate its utility. The performance of RAMSY is typically better than the results from correlation methods. RAMSY promises to improve unknown metabolite identification for MS users in metabolomics or other fields.

Caracterização da contribuição da albumina para a formação do espectro de ressonância magnética nuclear (RMN) do plasma sanguíneo

The plasma represents a average of the information referring biochemists to the physiology of the organism as a whole, therefore it indirectly or directly interacts with all tissues of the body. In such a way the plasma can be considered as a metabolic “soup”. Using the Nuclear Magnetic Resonance Spectroscopy sanguineous plasma spectra had been generated and using deconvolution techniques it was possible to know the contribution of the albumin for the formation of the spectra of the sanguineous plasma

Modificação superficial de nanopartículas de óxido de ferro por poli(ácido aspártico) reticulado

Pós-graduação em Química - IQ