RESUMO
The present work describes the construction and application of a simple, low cost and sensitive microfluidic paper-based device with electrochemical detection for the detection of paracetamol and 4-aminophenol. The separation channels of a width of 2.0 mm were created on paper using a wax printing process to define the regions of the device. A baseline separation level of the analytes can be obtained in 0.1 mol L(-1) acetate buffer solution at pH 4.5 and by injecting 500 nL of the standard solutions at 12 mm from the working electrode. The electrochemical detection system was created at the end of the channels through a process known as sputtering. The previously separated analytes were detected at the end of the hydrophilic separation channel by applying a potential of 400 mV vs. pseudo Au on the working electrode. Experimental variables such as type of paper (cation exchanger and n1), pH, sample volume, applied potential and distance of sample injection were evaluated and, under the conditions of higher response, it was possible to obtain detection limits of 25.0 and 10.0 µmol L(-1) for paracetamol and 4-aminophenol, respectively.
Assuntos
Acetaminofen/análise , Aminofenóis/análise , Antipiréticos/análise , Eletrocromatografia Capilar/instrumentação , Técnicas Eletroquímicas/instrumentação , Técnicas Analíticas Microfluídicas/métodos , Eletrocromatografia Capilar/métodos , Técnicas Eletroquímicas/métodos , Eletrodos , Limite de Detecção , PapelRESUMO
We report a new method of immobilization of gold nanoparticles (AuNPs) on a fused-silica capillary through covalent binding. The resulting modified capillary was applied to electrophoretic systems to improve the efficiency of separation and the selectivity of selected solutes. The immobilization of AuNPs on the capillary wall was performed in a very simple and fast way without requiring heating. The surface features of an AuNP-coated capillary column were determined using the scanning electron microscopy. The chromatographic properties of AuNP-coated capillaries were investigated through variation of the buffer pH and separation voltage. Effective separations of synthetic peptides mixture were obtained on the AuNP-coated capillaries. The method shows a remarkable stability since it was reused about 900 times. The capacity factor was duplicated. Therefore, this modification is stable and can be applied to different separation purposes. A complex mixture of tryptic peptide fragments of HSA was analyzed in both the bare- and the AuNP-coated capillaries. Better electrophoretic peptide profile was observed when using the AuNP-coated capillary.
Assuntos
Eletrocromatografia Capilar/instrumentação , Eletrocromatografia Capilar/métodos , Ouro/química , Nanopartículas Metálicas/química , Peptídeos/análise , Proteínas/análise , Humanos , Concentração de Íons de Hidrogênio , Microscopia Eletrônica de Varredura , Fragmentos de Peptídeos/análise , Fragmentos de Peptídeos/isolamento & purificação , Peptídeos/isolamento & purificação , Proteínas/isolamento & purificação , Espectrofotometria Ultravioleta , Tripsina/químicaRESUMO
The inner surface of fused silica capillaries has been covalently modified with different porphyrins (deuteroporphyrin, complexes of deuteroporphyrin with metal ions Fe(III), Cu(II), Zn(II), Ni(II), and Cu(II)-meso-tetra (carboxyphenyl) porphyrin) and it was applied for the separation of biologically active peptides by open-tubular capillary electrochromatography. Separations were performed in a mobile phase composed of 25 mM potassium phosphate, pH 4.0, 5% v/v ACN and 10 mM hydroquinone. Changes in the effective electrophoretic mobility of peptides were studied concerning porphyrin central metal atom, attachment geometry, and the presence of coordinating or aromatic amino acid residues in the peptide sequence. The results showed that differences in metal core on the porphyrin and the spatial conformation of attached porphyrin result in changes in the analyte interaction with the stationary phase.
Assuntos
Eletrocromatografia Capilar/instrumentação , Deuteroporfirinas/química , Mesoporfirinas/química , Metais Pesados/química , Neuropeptídeos/análise , Eletrocromatografia Capilar/métodos , Modelos Moleculares , Neuropeptídeos/química , Estatísticas não ParamétricasRESUMO
The separation of seven biologically active peptides was attempted by open-tubular capillary electrochromatography in fused-silica capillaries chemically modified with iron (III)-deuteroporphyrin using UV-absorption detection at 214 nm. The effect of BGE pH and content of organic solvent modifier was investigated. The best separations were obtained in 25 mM phosphate (BGE), pH 4.0, containing 5% v/v ACN and 10 mM hydroquinone, which was added to prevent gas bubble formation. Considering the method sensitivity, lower concentration LODs were obtained for all peptides in their open-tubular capillary electrochromatography separation as compared with their CZE separation in bare fused-silica capillary. The iron (III)-deuteroporphyrin column proved to be highly stable over time and showed acceptable precision of migration times and corrected peak areas (RSD in the range 2-4%).