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1.
Sci Technol Adv Mater ; 20(1): 657-672, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31275458

RESUMO

Metal oxide nanoparticles of different nature have been used in different fields such as therapeutics, biomarkers, tribology or environmental remediation, among others. Besides, the surface modification of such nanoparticles is of particular interest to bring designed functions. In this paper we describe the synthesis of CuO nanoparticles with two different geometries (spherical and prolate) and decorated with long alkyl chains in order to use as dye removers by adsorption and/or photo-degradation of a persistent model dye (Congo Red) and as lubricant additives to improve the tribological performance of base lubricant oils. Alkyl-functionalized CuO nanoparticles demonstrated a high stability in oily suspensions and an improvement in the friction reducing the CoF ca. 26%; the alkyl-decorated nanoparticles showed also higher adsorption kinetics for Congo Red than the neat ones following a pseudo-second-order trend, although with lower adsorption efficiency. The synthesis, surface modification and physic-chemical characterization of spherical and prolate CuO nanoparticles are described as well as their applications as lubricant additives and Congo Red photocatalytic removal.

2.
Nanotechnology ; 28(49): 495704, 2017 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-29035276

RESUMO

One of the main drawbacks in the application of metal-oxide nanoparticles as lubricant additives is their poor stability in organic media, despite the good anti-wear, friction-reducing and high-load capacity properties described for these materials. In this work, we present a novel procedure to chemically cap the surface of ZrO2 nanoparticles (ZrO2NPs) with long hydrocarbon chains in order to obtain stable dispersions of ZrO2NPs in non-aqueous media without disrupting their attributes as lubricant additives. C-8, C-10 and C-16 saturated flexible chains were attached to the ZrO2NP surface and their physical and chemical characterization was performed by transmission electron microscopy, thermogravimetric analysis, attenuated total reflectance Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy and solid-state nuclear magnetic resonance. The dispersion stability of the modified ZrO2NPs in non-aqueous media was studied using static multiple light scattering. Tribological tests demonstrated that dispersions of the long-chain capped ZrO2NPs in base lubricating oils exhibited low friction coefficients and improved the anti-wear properties of the base oil when compared with the raw lubricating oil.

3.
Sci Technol Adv Mater ; 16(5): 055005, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27877840

RESUMO

Silica nanoparticles (SiO2 NPs) synthesized by the sol-gel approach were engineered for size and surface properties by grafting hydrophobic chains to prevent their aggregation and facilitate their contact with the phase boundary, thus improving their dispersibility in lubricant base oils. The surface modification was performed by covalent binding of long chain alkyl functionalities using lauric acid and decanoyl chloride to the SiO2 NP surface. The hybrid SiO2 NPs were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, simultaneous differential thermal analysis, nuclear magnetic resonance and dynamic light scattering, while their dispersion in two base oils was studied by static multiple light scattering at low (0.01% w/v) and high (0.50%w/v) concentrations. The nature of the functional layer and the functionalization degree seemed to be directly involved in the stability of the suspensions. The potential use of the functional SiO2 NPs as lubricant additives in base oils, specially designed for being used in hydraulic circuits, has been outlined by analyzing the tribological properties of the dispersions. The dendritic structure of the external layer played a key role in the tribological characteristics of the material by reducing the friction coefficient and wear. These nanoparticles reduce drastically the waste of energy in friction processes and are more environmentally friendly than other additives.

4.
BMC Fam Pract ; 13: 35, 2012 May 02.
Artigo em Inglês | MEDLINE | ID: mdl-22551252

RESUMO

BACKGROUND: Medically unexplained symptoms are an important mental health problem in primary care and generate a high cost in health services.Cognitive behavioral therapy and psychodynamic therapy have proven effective in these patients. However, there are few studies on the effectiveness of psychosocial interventions by primary health care. The project aims to determine whether a cognitive-behavioral group intervention in patients with medically unexplained symptoms, is more effective than routine clinical practice to improve the quality of life measured by the SF-12 questionary at 12 month. METHODS/DESIGN: This study involves a community based cluster randomized trial in primary healthcare centres in Madrid (Spain). The number of patients required is 242 (121 in each arm), all between 18 and 65 of age with medically unexplained symptoms that had seeked medical attention in primary care at least 10 times during the previous year. The main outcome variable is the quality of life measured by the SF-12 questionnaire on Mental Healthcare. Secondary outcome variables include number of consultations, number of drug (prescriptions) and number of days of sick leave together with other prognosis and descriptive variables. Main effectiveness will be analyzed by comparing the percentage of patients that improve at least 4 points on the SF-12 questionnaire between intervention and control groups at 12 months. All statistical tests will be performed with intention to treat. Logistic regression with random effects will be used to adjust for prognostic factors. Confounding factors or factors that might alter the effect recorded will be taken into account in this analysis. DISCUSSION: This study aims to provide more insight to address medically unexplained symptoms, highly prevalent in primary care, from a quantitative methodology. It involves intervention group conducted by previously trained nursing staff to diminish the progression to the chronicity of the symptoms, improve quality of life, and reduce frequency of medical consultations. TRIAL REGISTRATION: The trial was registered with ClinicalTrials.gov, number NCT01484223 [http://ClinicalTrials.gov].


Assuntos
Terapia Cognitivo-Comportamental/métodos , Atenção Primária à Saúde/métodos , Psicoterapia de Grupo/métodos , Transtornos Somatoformes/terapia , Adolescente , Adulto , Idoso , Feminino , Humanos , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Qualidade de Vida , Encaminhamento e Consulta/estatística & dados numéricos , Licença Médica/estatística & dados numéricos , Espanha , Inquéritos e Questionários , Resultado do Tratamento , Adulto Jovem
5.
Antioxidants (Basel) ; 11(11)2022 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-36358565

RESUMO

The deterioration of oil-based products during processing, distribution and storage has a major negative impact on the industry from an economic point of view. The spoilage of oil is mainly due to its oxidation which can be triggered by various factors, such as UV light, heating or the presence of impurities that result in the formation of radical species. In this context, several packaging alternatives have recently been developed with the aim to protect and extend the shelf life of oil-based products. This work aimed to study the antioxidant properties of bio-polymer-based films (BPFs) obtained from high methoxylated pectin (HMP) and sodium caseinate (CAS) and enriched with different concentrations of green carbon dots (gCDs), 0.25%, 0.50 and 1% w/w, obtained from apple pomace (APCDs) and rosemary powder (RCDs). The resulting films (gCDs-BPFs) have shown that the presence of gCDs not only modified the surface roughness of the films, but also positively affected their antioxidant properties. The addition of gCDs enhanced the radical inhibiting capacity of the raw BPFs by 42 and 62% for the films containing 1% RCDs and 1% APCDs, respectively. As a proof of the concept, two oil samples (edible and cosmetic) were treated with the obtained antioxidant films, and the results demonstrated that in both types of samples the oxidation process was minimized during the five days of the experiment. These results are promising and suggest that the antioxidant bio-polymer-based films could be excellent candidates for further production of active packaging.

6.
J Med Entomol ; 59(1): 314-319, 2022 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-34536077

RESUMO

Mass-trapping has been used to control outbreaks of Aedes aegypti (Linnaeus) (Diptera: Culicidae) in Puerto Rico since 2011. We investigated the effect of multi-year, insecticide-free mass trapping had on the insecticide susceptibility profile of Ae. aegypti. Eggs collected in southern Puerto Rico were used to generate F1 populations that were tested for susceptibility to permethrin, sumethrin, bifenthrin, deltamethrin, and malathion according to CDC bottle bioassays protocols. All populations of Ae. aegypti were resistant to the synthetic pyrethroids and mosquitoes from two locations were partially resistant to malathion. Population genetic analysis, using a double digest restriction sites associated DNA sequencing (ddRADseq) approach, indicated a large amount of migration between study sites effectively homogenizing the mosquito populations. Mass-trapping using noninsecticidal autocidal gravid ovitraps did not restore susceptibility to five active ingredients that are found in commercial insecticides. Migration between communities was high and would have brought outside alleles, including resistant alleles to the treatment communities. Further investigation suggests that household use of commercially available insecticide products may continue to select for resistance in absence of public health space spraying of insecticides.


Assuntos
Aedes , Genética Populacional , Resistência a Inseticidas/genética , Aedes/efeitos dos fármacos , Aedes/genética , Distribuição Animal , Animais , Genes de Insetos , Inseticidas/farmacologia , Malation/farmacologia , Mosquitos Vetores/efeitos dos fármacos , Mosquitos Vetores/genética , Permetrina/farmacologia , Porto Rico , Piretrinas/farmacologia
7.
Membranes (Basel) ; 12(7)2022 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-35877898

RESUMO

Nowadays, proteins and polysaccharides play a fundamental role in the manufacturing of biocompatible materials applied in food packaging. The resulting films have, however, limits associated with the resistance to mechanical stress; therefore, it is important to reinforce the initial mixture with additives that promote the development of stronger molecular links. Carbon dots (CDs) are excellent candidates for this purpose due to the presence of surface functional groups that determine the formation of numerous intramolecular bonds between the charged biopolymers. The present research aims to evaluate the effect of CDs on the mechanical properties of biopolymer films obtained from sodium caseinate (CAS), high methoxyl pectin (HMP) and glycerol used as plasticizers. Green carbon dots (gCDs) were obtained from natural organic sources by green synthesis. The effects of gCDs on the flow behavior and viscoelastic properties of mixed biopolymer dispersions and the thermophysical properties of the corresponded films were evaluated by steady and unsteady shear rheological measurements and differential scanning calorimetry (DSC) tests, respectively. The dynamic mechanical measurements were realized taking into account the parameters of temperature and relative humidity. The results indicate a significant change in the viscosity of the protein-polysaccharide dispersions and the thermomechanical properties of the corresponding film samples reinforced with higher amounts of gCDs.

8.
ACS Sustain Chem Eng ; 9(4): 1459-1476, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-35273833

RESUMO

Lipids are widely distributed in nature and are one of the most important components of natural foods, synthetic compounds, and emulsions. To date, there is a strong social demand in the industrial sector for the use of sustainable products with a minimal environmental impact. Depending on their origin and composition, lipids can be employed as a plausible alternative as biodegradable lubricants in order to reduce the use of conventional mineral oil lubricants and mitigate their environmental impact. This perspective provides an overview of the advantages and constrains of vegetal oils under different lubrication regimes and the tribochemical reactions that can take place. Also, the different factors and pathways that influence their oxidation, the key role of moisture, and the changes of physical properties under pressure and temperature are reviewed. Special emphasis is devoted to the oxidation instability of fatty acids and vegetal oils and the physical and chemical approaches to improve oxidative and thermal stability are described in detail.

9.
Appl Environ Microbiol ; 76(10): 3401-4, 2010 May.
Artigo em Inglês | MEDLINE | ID: mdl-20348294

RESUMO

Vital stains were used in combination with fluorimetry for the elaboration of a new method to quantify Streptomyces programmed cell death, one of the key events in Streptomyces differentiation. The experimental approach described opens the possibility of designing online protocols for automatic monitoring of industrial fermentations.


Assuntos
Apoptose , Técnicas Bacteriológicas/métodos , Microbiologia Industrial/métodos , Streptomyces/citologia , Streptomyces/crescimento & desenvolvimento , Fermentação
10.
Molecules ; 15(6): 4017-32, 2010 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-20657423

RESUMO

Quantum chemical calculations were performed to characterize the interaction of the flavonol molecule (FL) with methacrylic acid (MAA) and 4-vinylpyridine (4VPy) in the formation of imprinted polymers. The polarizable continuum model (PCM) was used to gain insight on the type of interaction between the reactant molecules under vacuum conditions and in the presence of different solvents. The effect of solvent on the pre-polymerization complex formation was evaluated through the stability energy, in which chloroform behaves as the best solvent for the synthesis of the imprinted polymers since it facilitates the reaction by lowering its degree of stabilization. The reactivity was analyzed in terms of the electrostatic surface potential (ESP) and Mulliken charge. By means of these results, it has been possible to determine two potential recognition sites for the interaction of the MAA monomer and one for the 4VPy in relation to the strength of interaction with FL. In this concern, the interaction of the system FL-MAA is stronger than FL-4VPy.


Assuntos
Flavonóis/química , Metacrilatos/química , Impressão Molecular/métodos , Polímeros/química , Piridinas/química , Espectroscopia de Ressonância Magnética , Modelos Moleculares
11.
Antioxidants (Basel) ; 9(11)2020 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-33228081

RESUMO

Carbon dots (CDs) due to their unique optical features, chemical stability and low environmental hazard are applied in different fields such as metal ion sensing, photo-catalysis, bio-imaging and tribology, among others. The aims of the present research were to obtain CDs from vegetable wastes (tea and grapes) as carbon sources and to explore their potential properties as radical scavengers. CDs from glutathione/citric acid (GCDs) were synthetized for comparison purposes. The CDs were investigated for their chemical structure, morphology, optical and electronical properties. The antioxidant activity has been explored by DPPH and Folin-Ciocelteau assays in aqueous media. Due to their solubility in oil, the CDs prepared from tea wastes and GCDs were assayed as antioxidants in a mineral oil lubricant by potentiometric determination of the peroxide value. CDs from tea wastes and GCDs exhibited good antioxidant properties both in aqueous and oil media. Possible mechanisms, such as C-addition to double bonds, H-abstraction and SOMO-CDs conduction band interaction, were proposed for the CDs radical scavenging activity. CDs from natural sources open new application pathways as antioxidant green additives.

12.
Talanta ; 219: 121312, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32887052

RESUMO

The presence of water in lubricant oils is a parameter related to the lubricant deterioration, which can be indicative of a serious loss of tribological efficiency and, therefore, an increase in maintenance costs. Likewise, controlling the aging of the lubricant oil is a keynote issue to prevent damage on the lubricated surfaces (e.g. engine pieces). The combination of Attenuated Total Reflectance (ATR) techniques with Fourier-Transform Infrared Spectrometry (FTIR) result in an easy, simple, fast and non-destructive way for obtaining accurate information about the actual situation of a lubricant oil. The analysis of this ATR-FTIR information using Artificial Neural Networks (ANN) as well as Linear Discriminant Analysis (LDA) results in the proper classification of lubricant oils regarding the presence/absence of water, age and viscosity. The methodology proposed in this work describes procedures for identifying the deterioration degree of oils with as high as 100% success (aging week) or 97.7% (for viscosity and water presence).

13.
Med Clin (Barc) ; 152(11): 431-437, 2019 06 07.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-30314739

RESUMO

BACKGROUND AND OBJECTIVE: Several trials have evaluated the effect of disease management programs in heart failure (HF) with diverse results. The aim of this study was to develop a simple nurse-led clinic intervention program for patients with HF and assess whether this intervention positively affects the prognosis of patients, their care costs and perceived quality of life (QoL). METHODS: Between 2011 and 2013, 127 patients with reduced ejection fraction were prospectively randomly allocated (1:2) to standard care or intervention program. Primary composite endpoint was all-cause mortality and hospital readmissions. Secondary endpoints were all-cause mortality, all-cause hospital readmissions, readmissions for HF, time to first readmission and QoL improvements assessed by "Minnesota Living with Heart Failure Questionnaire" (MLHFQ). An intention-to-treat analysis was performed. RESULTS: After a median follow-up of 2-years, no differences were found in the primary composite endpoint. Likewise, there were no differences between groups in the predefined secondary endpoints of mortality and readmissions from any cause. However, in the intervention group, readmissions for HF were significantly reduced (35% vs. 18%; p=0.04) and QoL significantly improved (MLHFQ±SD: 2.29±14 vs. 10.9±14.75; p=0.04). CONCLUSIONS: In patients with HF, the use of a nurse-led intervention program significantly improves perceived QoL and reduce HF hospital readmissions.


Assuntos
Gerenciamento Clínico , Insuficiência Cardíaca/terapia , Pesquisa em Avaliação de Enfermagem/métodos , Readmissão do Paciente , Qualidade de Vida , Idoso , Idoso de 80 Anos ou mais , Feminino , Seguimentos , Custos de Cuidados de Saúde , Insuficiência Cardíaca/economia , Insuficiência Cardíaca/mortalidade , Humanos , Masculino , Pessoa de Meia-Idade , Prognóstico , Inquéritos e Questionários
14.
Biosens Bioelectron ; 23(7): 1101-8, 2008 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-18164194

RESUMO

Organically modified molecularly imprinted silicas (MIS) for nafcillin recognition were prepared using a simple sol-gel procedure. Molecular recognition of the template was observed by tuning the chemical and structural properties of the MIS. The relative amounts of organically modified alkoxysilane precursors were found to be key in the textural and morphological characteristics of the MIS as well as for developing an imprinting effect in the materials. The recognition properties of the imprinted materials were found to be strongly influenced by the hydrolytic stability of the alkoxysilanes and their inductive effects during sol-gel hydrolysis/condensation stages. The concept was to combine properties of organic groups with those of glass-like materials in order to develop synergetic properties through variations in the composition. Results from batch rebinding experiments as well as from the thorough study of the N(2) adsorption properties and the textural and structural characteristics of the MIS revealed that an imprint effect could be attributed to the presence of the template during the synthesis of MIS.


Assuntos
Materiais Revestidos Biocompatíveis/química , Nafcilina/química , Adesividade , Adsorção , Géis , Teste de Materiais , Porosidade , Propriedades de Superfície
15.
Psicothema ; 20(4): 610-5, 2008 Nov.
Artigo em Espanhol | MEDLINE | ID: mdl-18940058

RESUMO

Although online psychological services and research based on them are increasing rapidly, it is not that easy to find investigations that focus on the kind of people that demand them. To know their profile could help to improve the online psychological services that are offered to them. For this purpose, we analysed the sociodemographic characteristics of 1052 participants, all of them having posed a psychological question to our online advice service. The relations between sociodemographics and variables related to the psychological consultation are analysed herein. Features such as age distribution, a high proportion of long-term problems, the large quantity of questions from Latin America, or the under representation of the lowest socioeconomic and educational levels could lead to clinical, social and legal implications that we comment on in this work.


Assuntos
Aconselhamento , Internet , Adolescente , Adulto , Demografia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Psicologia
16.
J Agric Food Chem ; 55(3): 566-70, 2007 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-17263442

RESUMO

A study has been made of the analytical application of a nafcillin-imprinted sol-gel to the direct determination of the beta-lactamic antibiotic in spiked milk-based samples using a room temperature phosphorescent flow-through system. The influence of the sample matrix on the transduction and the recognition processes was statistically determined, and results demonstrated that the imprinted sol-gel optosensing system could be effectively applied to real sample analysis. The analytical performance characteristics were as follows: The detection limit results for aqueous and skimmed milk were 5.8 x 10(-6) and 3.3 x 10(-5) mol L(-1), respectively, and a relative standard deviation less than 5% was found for both matrices. Statistical analysis of variance studies have been shown to have no significant effect on different skimmed milk commercial products over the imprinted material recognition. This fact provides an indicator of the ruggedness/robustness of the proposed analytical system and the possibility to use external real matrix calibration. Application of the method to nafcillin analysis in other milk-based samples is outlined.


Assuntos
Antibacterianos/análise , Leite/química , Nafcilina/análise , Animais , Fenômenos Químicos , Físico-Química , Análise de Injeção de Fluxo , Transição de Fase , Espectrofotometria
17.
J Biomed Nanotechnol ; 13(2): 167-79, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29377647

RESUMO

In this study, the in vitro uptake by fibroblasts and in vivo biodistribution of 15 nm 11-mercaptoundecanoicacid-protected gold nanoparticles (AuNPs-MUA) and 3 nm glutathione- and 3 nm bovine serum albumin-protected gold nanoclusters (AuNCs@GSH and AuNCs@BSA, respectively) were evaluated. In vitro cell viability was examined after gold nanoparticle treatment for 48 h, based on MTT assays and analyses of morphological structure, the cycle cell, cellular doubling time, and the gold concentration in cells. No potential toxicity was observed at any studied concentration (up to 10 ppm) for AuNCs@GSH and AuNCs@BSA, whereas lower cell viability was observed for AuNPs-MUA at 10 ppm than for other treatments. Neither morphological damage nor modifications to the cell cycle and doubling time were detected after contact with nanoparticles. Associations between cells and AuNPs and AuNCs were demonstrated by inductively coupled plasma mass spectrometry (ICP-MS). AuNCs@GSH exhibited fluorescence emission at 611 nm, whereas AuNCs@BSA showed a band at 640 nm. These properties were employed to confirm their associations with cells by fluorescence confocal microscopy; both clusters were observed in cells and maintained their original fluorescence. In vivo assays were performed using 9 male mice treated with 1.70 µg Au/g body weight gold nanoparticles for 24 h. ICP-MS measurements showed a different biodistribution for each type of nanoparticle; AuNPs-MUA mainly accumulated in the brain, AuNCs@GSH in the kidney, and AuNCs@BSA in the liver and spleen. Spleen indexes were not affected by nanoparticle treatment; however, AuNCs@BSA increased the thymus index significantly from 1.28 to 1.79, indicating an immune response. These nanoparticles have great potential as organ-specific drug carriers and for diagnosis, photothermal therapy, and imaging.


Assuntos
Ouro/química , Ouro/farmacocinética , Nanopartículas Metálicas/química , Animais , Sobrevivência Celular/efeitos dos fármacos , Glutationa , Ouro/toxicidade , Fígado/química , Fígado/metabolismo , Masculino , Nanopartículas Metálicas/toxicidade , Camundongos , Camundongos Endogâmicos C57BL , Células NIH 3T3 , Soroalbumina Bovina , Baço/química , Baço/metabolismo , Distribuição Tecidual
18.
Anal Chim Acta ; 666(1-2): 1-22, 2010 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-20433959

RESUMO

Multifunctional nanoparticles are among the most exciting nanomaterials with promising applications in analytical chemistry. These applications include (bio)sensing, (bio)assays, catalysis and separations. Although most of these applications are based on the magnetic, optical and electrochemical properties of multifunctional nanoparticles, other aspects such as the synergistic effect of the functional groups and the amplification effect associated with the nanoscale dimension have also been observed. Considering not only the nature of the raw material but also the shape, there is a huge variety of nanoparticles. In this review only magnetic, quantum dots, gold nanoparticles, carbon and inorganic nanotubes as well as silica, titania and gadolinium oxide nanoparticles are addressed. This review presents a narrative summary on the use of multifunctional nanoparticles for analytical applications, along with a discussion on some critical challenges existing in the field and possible solutions that have been or are being developed to overcome these challenges.


Assuntos
Técnicas de Química Analítica/métodos , Nanopartículas/química , Animais , Carbono/química , Ouro/química , Humanos , Magnetismo , Pontos Quânticos
19.
Anal Biochem ; 341(1): 113-21, 2005 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-15866535

RESUMO

Degradation of beta-lactam antibiotics by means of metallic cations seems to have a very complex chemistry, involving not only the catalytic effect of the metal ion but also complex formation. Many different compounds, such as methylpyrazines, oxazolones, penicilloic, penicillenic, and penicillonic acids, have been reported as degradation products of such antibiotics, although not many details about the progress of the reaction can be found in the literature. Two novel fluorimetric and spectrophotometric methods previously published by the authors, as well as kinetic studies, have been used to propose a possible reaction mechanism for the ampicillin degradation in the presence of copper(II) ions. Likewise, we have proposed the chemical structure required by the beta-lactam antibiotics to develop absorption or fluorescence properties. Kinetics in micellar and aqueous media shows that the copper-ampicillin reaction proceeds through different pathways depending on the reaction medium.


Assuntos
Antibacterianos/metabolismo , Cobre/metabolismo , beta-Lactamas/metabolismo , Ampicilina/metabolismo , Antibacterianos/química , Cobre/química , Concentração de Íons de Hidrogênio , Cinética , Micelas , Espectrometria de Fluorescência , Espectrofotometria Infravermelho , Espectrofotometria Ultravioleta , Água , beta-Lactamas/química
20.
J Sep Sci ; 28(5): 453-61, 2005 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-15835733

RESUMO

New materials based on molecularly imprinted polymers (MIPs) have been developed for use as sorbents in solid phase extraction to preconcentrate some urea herbicides. In the preconcentration step, different molecularly imprinted polymers were tested using methacrylic acid (MAA) and 2-(trifluoromethyl)acrylic acid (TFMAA) as functional monomers, and linuron and isoproturon as templates. The best results were obtained when the polymer was synthesised using MAA with isoproturon as template. Another parameter evaluated was the way in which the polymer was obtained. We observed that the imprinted polymers obtained by precipitation displayed a greater capacity to retain the phenylureas. Studies conducted using scanning electron microscopy (SEM) revealed that the bulk polymerisation method is far from ideal owing to the random shape and size distribution of the particles obtained, whereas when polymerisation was carried out in precipitation microspheres were obtained. In order to confirm the interaction between the functional monomer and the template, 1H NMR (CD2Cl2) analyses were conducted. The results obtained suggest that the hydrogen and/or nitrogen of the amino group of the template would be involved in the formation of hydrogen bonds with the functional monomer. The imprinted polymer obtained by precipitation polymerisation with MAA as functional monomer and isoproturon as template can be applied to preconcentrate phenylureas when the sample is dissolved in toluene. The proposed methodology was employed to evaluate polymer selectivity towards humic acids and towards other herbicides.


Assuntos
Herbicidas/análise , Herbicidas/química , Compostos de Fenilureia/análise , Compostos de Fenilureia/química , Polímeros/química , Polímeros/síntese química , Precipitação Química , Espectroscopia de Ressonância Magnética , Microscopia Eletrônica de Varredura , Estrutura Molecular , Sensibilidade e Especificidade
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