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Coltro W.K.T.,University of Sao Paulo | Coltro W.K.T.,Instituto Nacional Of Ciencia E Tecnologia Of Bioanalitica Inctbio | Coltro W.K.T.,Federal University of Goais | Neves R.D.S.,University of Sao Paulo | And 6 more authors.
Sensors and Actuators, B: Chemical | Year: 2014

This paper describes the fabrication of microfluidic devices with integrated dual capacitively coupled contactless conductivity detection (C 4D) for monitoring binding events. The avidin-biotin model was employed to show the feasibility of the C4D as a detection mode. The binding event was monitored using microfluidic channels fabricated in poly(dimethylsiloxane) (PDMS). Detection electrodes were fabricated in a three-electrode arrangement by sputtering a Ti/Au/Ti layer over a glass wafer, which were electrically insulated by a SiO2 layer. The dielectric layer over the sensing electrode area was chemically modified with biotin. After introducing avidin solutions on microchannels, binding events were detected on conductivity sensorgrams by applying a 300-kHz-sinusoidal waveform with amplitude of 2 V (peak-to-peak) to the exciting electrode. The electrical characterization of the modified electrode indicates that the conductivity signal is changed due to the alteration on the dielectric constant of the surface. The limit of detection for avidin was 1.5 μg mL-1, representing 23 nmol L-1. © 2013 Elsevier B.V. Source


Pessoa De Santana P.,Federal University of Minas Gerais | Segato T.P.,University of Sao Paulo | Segato T.P.,Instituto Nacional Of Ciencia E Tecnologia Of Bioanalitica Inctbio | Carrilho E.,University of Sao Paulo | And 6 more authors.
Analyst | Year: 2013

This communication describes a simple and cost-effective method for fabricating glass microchannels by wet chemical etching using masks made by xurography in vinyl adhesive films. Analytical performance of microfluidic devices fabricated using the new approach was evaluated by microchip electrophoresis coupled to capacitively coupled contactless conductivity detection (C4D) and laser-induced fluorescence (LIF) detection. This journal is © The Royal Society of Chemistry. Source


Saito R.M.,University of Campinas | Coltro W.K.T.,Federal University of Goais | Coltro W.K.T.,Instituto Nacional Of Ciencia E Tecnologia Of Bioanalitica Inctbio | De Jesus D.P.,University of Campinas | De Jesus D.P.,Instituto Nacional Of Ciencia E Tecnologia Of Bioanalitica Inctbio
Electrophoresis | Year: 2012

Reproducible and representative sample injection in microchip electrophoresis has been a bottleneck for quantitative analytical applications. Electrokinetic sample injection is the most used because it is easy to perform. However, this injection method is usually affected by sample composition and the bias effect. On the other hand, these drawbacks are overcome by the hydrodynamic (HD) sample injection, although this injection mode requires HD flow control. This review gives an overview of the basic principles, the instrumentation designs, and the performance of HD sample injection systems for microchip electrophoresis. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Aguiar V.S.,University of Campinas | Aguiar V.S.,Instituto Nacional Of Ciencia E Tecnologia Of Bioanalitica Inctbio | Bottoli C.B.G.,University of Campinas | Bottoli C.B.G.,Instituto Nacional Of Ciencia E Tecnologia Of Bioanalitica Inctbio
Instrumentation Science and Technology | Year: 2015

Octadecyl methacrylate-based monolithic capillary columns were prepared using octadecyl methacrylate as the monomer, ethylene dimethacrylate as the cross-linking agent, 2-acryloylamido-2-methylpropanesulfonic acid as the ionizable monomer, responsible for a negatively charged stationary phase surface and able to support a cathodic electrosmotic flow, and amyl alcohol and 1,4-butanediol as porogenic solvents. The repeatability of the morphological aspect of the monolithic material was evaluated by scanning electron microscopy (SEM). The uniformity along the same monolithic bed was also investigated by SEM. Replicate determinations of surface area and pore volume were also performed and compared. The repeatability of the obtained electrochromatographic efficiencies for separations of alkylbenzenes using the stationary phases prepared was also evaluated. A column that had a plate height of 31 μm was tested for separation of polycyclic aromatic hydrocarbons. Even though minimal possible variation of experimental parameters was maintained, it was not possible to reproduce the stationary phases of the monolithic columns, since the relative standard deviation for the efficiencies obtained on columns prepared from the same polymerization mixture composition was 62%. The lack of repeatability for the efficiency is thought to be a result of limited homogeneity of the monolithic globular structures along the length of the majority of the prepared columns. The poor precision of preparation was justified by the copolymerization reaction that occurs in the presence of 2, 2′-azobisisobutyronitrile as the initiator agent, whose decomposition starts at the moment that this is added to the reaction mixture. Copyright © Taylor & Francis Group, LLC. Source


Aguiar V.S.,University of Campinas | Aguiar V.S.,Instituto Nacional Of Ciencia E Tecnologia Of Bioanalitica Inctbio | Bottoli C.B.G.,University of Campinas | Bottoli C.B.G.,Instituto Nacional Of Ciencia E Tecnologia Of Bioanalitica Inctbio
Microchemical Journal | Year: 2013

Monolithic poly(octadecyl methacrylate-. co-ethylene dimethacrylate) capillary columns for use in capillary electrochromatography (CEC) were developed and characterized by porosimetric measurements and scanning electron microscopy (SEM). The stationary phases were prepared using 2-acryloylamido-2-methylpropanesulfonic acid (AMPS) as the ionizable monomer and 2,2'-azobisisobutyronitrile (AIBN) as the initiator of thermal polymerization, which occurred at 60. °C. The porogenic solvents used in this work were amyl alcohol and 1,4-butanediol, in the proportion 65:35 (v/v). The ratio between monomers and porogenic solvents was varied in a range of 60 to 80% (v/v) of porogenic agents. The porosimetry showed that the increase in content of porogenic solvents caused an increase in pore surface area, but a relationship with the separation efficiencies was not observed. SEM agreed with the conclusions made through porosimetry, where decreases in globule size could be noted with increases in porogenic solvents. © 2012 Elsevier B.V. Source

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