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1.
Phys Chem Chem Phys ; 17(1): 414-21, 2015 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-25407573

RESUMO

The interaction of Co hexagonal magnetic nanoparticles (MNPs) with distearoyl phosphatidyl glycerol (DSPG) and distearoyl phosphatidic acid (DSPA) films adsorbed at a water/1,2-dichloroethane interface is studied employing cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), capacity curves and interfacial pressure-area isotherms. DSPA and DSPG adsorb at the interface forming homogenous films and producing a blocking effect on the transfer process of tetraethyl ammonium (TEA(+)), used as a probe cation. In the presence of Co NPs this effect is reversed and the reversible transfer process for TEA(+) is reestablished, to a greater or lesser extent depending on the structuration of the film. Co-DSPA hybrid films have a homogeneous structure while Co-DSPG films present different domains. Moreover, the presence of Co on DSPA film modifies the partition coefficient of the organic electrolyte into the hydrocarbon layer.


Assuntos
Nanopartículas de Magnetita/química , Fosfolipídeos/química , Adsorção , Dicloretos de Etileno/química , Ácidos Fosfatídicos/química , Fosfatidilgliceróis/química , Propriedades de Superfície , Água/química
2.
Talanta ; 83(2): 623-30, 2010 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-21111183

RESUMO

The quantitative determination of boldine alkaloid in boldo leaf extracts by employing cyclic voltammetry, at a liquid/liquid interface as well as the validation of this methodology against the reference method, high performance liquid chromatography (HPLC), are reported in the present paper. The voltammetric analysis was performed successfully and economically using two kinds of liquid/liquid interfaces: water/1,2-dicholoroethane and water/PVC (polyvinyl chloride)-gelled 1,2-dichloroethane. Linear calibration curves in the concentration range of 1.04 × 10(-5)mol L(-1) to 5.19 × 10(-4)mol L(-1) were obtained with a detection limit equal to (6.1 ± 0.7) × 10(-5)mol L(-1) and the quantitative determination of this alkaloid, in complex matrixes such as boldo leaf extracts, by the electrochemical technique proposed was found to be equal to the values obtained using the standard HPLC method. The validation analysis of this methodology against HPLC demonstrated that accuracy, linearity, limit of detection (LOD), limit of quantification (LOQ), specificity and precision are acceptable. The electroanalytical technique proposed is economical and selective, involves simple equipment and can be applied for the quantitative determination of boldine alkaloid in complex matrixes such as leaf extracts without special drug separation. Moreover, cyclic voltammetry (CV) experiments applied at the liquid/liquid interface under different experimental conditions allowed us to study the transfer mechanism of boldine, and determine a value of pK(a)(w)=6.90 for protonated boldine, from the variation of voltammetric peak current with pH.


Assuntos
Alcaloides/química , Aporfinas/análise , Cromatografia Líquida de Alta Pressão/métodos , Aporfinas/química , Calibragem , Calorimetria/métodos , Eletroquímica/métodos , Eletrodos , Modelos Químicos , Análise de Regressão , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Água/química
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