A instrumentação para a determinação fotométrica do fluxo eletrosmótico (EOF) em dispositivos microfluídicos é descrita neste trabalho. A instrumentação é baseada em componentes acessíveis e consiste em um microscópio trinocular e no fotodiodo integrado OPT101. Um diodo emissor de luz (LED) de alta intensidade foi utilizado como fonte de radiação. Para as determinações foram utilizadas soluções aquosas dos corantes azul patente V e azul de metileno. O sistema foi utilizado no monitoramento do EOF em microdispositivos de poli(dimetilsiloxano) (PDMS) e híbridos de toner/vidro. As mobilidades do EOF determinadas em pH 7,0 foram (5,75 ± 0,01)10-4 cm² V-1 s-1 e (3,2 ± 0,1)10-4 cm² V-1 s-1 para os dispositivos de toner/vidro e PDMS, respectivamente. Medidas reprodutíveis foram obtidas em todos os experimentos, levando a uma alta precisão na determinação. O método proposto foi comparado com o método tradicional de determinação do EOF que envolve a medida da corrente nos microcanais.

An instrumental setup for electroosmotic flow (EOF) determination in microfluidic devices is described. The system is based on a trinocular microscope and an integrated photodiode OPT101. The radiation was provided by a high-intensity white LED. For the determinations, patent blue V and methylene blue aqueous solutions were used. The setup was applied for EOF monitoring in hybrid toner/glass and PDMS microchips. For the toner/glass device, the EOF mobility was determined to be (5.75 ± 0.01) 10-4 cm² V-1 s-1 at pH 7.0. For PDMS devices the measured EOF mobility was (3.2 ± 0.1) 10-4 cm² V-1 s-1. Reproducible measurements were obtained in all experiments, which produced results with small errors. The proposed method was compared to the conventional current monitoring method.

Capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C4D) was used for determination of sodium and potassium concentrations in diet and non-diet soft drinks. Higher sodium concentrations were found in the diet samples due to the utilization of sodium salts of cyclamate and saccharine as sweeteners. The CE-C4D method can be used by food industries and health regulatory agencies for monitoring sodium and potassium content, not only in soft drink but in many others food products.

This is a contribution that presents a translation of the work "Terminology for Analytical Capillary Electromigration Techniques" by Riekkola and collaborators (Pure Appl. Chem., Vol. 76, No. 2, 443-451, 2004) from IUPAC© for the Portuguese Language. Additional terms that had not been defined in native Portuguese were included for the benefit of the local community. Additional notes were also included to clarify some important concepts and to highlight the differences between techniques.

This article describes the use of a conventional CRT monitor as a high voltage power supply for capillary electrophoresis. With this monitor, a 23-kV high voltage with a ripple of 1.32% was observed. The reproducibility of the applied high voltage was evaluated by measuring the standard deviations of peak area and migration time for five consecutive injections of a test mixture containing potassium, sodium, and lithium cations at 50 mmol L-1. The errors were about 2.5% and 0.6% for peak area and migration time, respectively. The maximum current tested was about 180 mA, which covers most capillary electrophoresis applications. This system has been successfully used for several months, maintaining the desired level of performance.

This article describes a novel approach to the separation of fatty acids ranging from 8 to 20 carbons using capillary electrophoresis with contactless conductivity detection. Complete separation of nine linear chain fatty acids (from C8:0 to C20:0) was achieved in 15 min under normal polarity operation. Limits of detection ranged from 35 to 319 µmol L-1 for C20:0 to C8:0, respectively. The optimized running electrolyte composition was 5.0 mmol L-1 phosphate buffer at pH 7, 4.0 mmol L-1 dimethyl-b-cyclodextrin, 2.0 mmol L-1 trimethyl-b-cyclodextrin, acetonitrile 50% (v/v), and methanol 20% (v/v). The applicability of the separation system was demonstrated by the analysis of coconut vegetable oil.

This review focuses the development of electrochemical detection systems coupled to capillary electrophoresis. Conductometric, amperometric, voltametric, and potentiometric modes of detection are reviewed. The positioning of the electrodes, interferences of high electric field, and the materials employed in the fabrication and modification of the electrodes are discussed. The advantages of the use of electrochemical detection with capillary electrophoresis, regarding to the sensitivity and selectivity, is exemplified with a large number of applications. Also, the use of electrochemical detection systems in microchip technology is addressed.

This technical note describes a new and simple electronic circuit for driving solenoid valves. The circuit is based on a single integrated circuit DRV103, which is able to drive resistive or inductive loads up to 1.5 A. Switching of 12-V loads can be controlled by TTLlevel signals in two distinct steps. Initially, 12 V is applied during 110 ms, followed by 4.2 V RMS until the end of the activation TTL pulse. This mode of operation is particularly suitable to drive solenoids, because it requires a higher voltage to start and a lower maintenance voltage. By using this circuit, power consumption and heating are reduced and the solenoid lifetime is enhanced. Moreover, this circuit is specially appropriated to build computercontrolled solenoid valves systems.