Dosil Pereira de Jesus

Toner and paper‐based fabrication techniques for microfluidic applications

The interest in low‐cost microfluidic platforms as well as emerging microfabrication techniques has increased considerably over the last years. Toner‐ and paper‐based techniques have appeared as two of the most promising platforms for the production of disposable devices for on‐chip applications. This review focuses on recent advances in the fabrication techniques and in the analytical/bioanalytical applications of toner and paper‐based devices. The discussion is divided in two parts dealing with (i) toner and (ii) paper devices. Examples of miniaturized devices fabricated by using direct‐printing or toner transfer masking in polyester‐toner, glass, PDMS as well as conductive platforms as recordable compact disks and printed circuit board are presented. The construction and the use of paper‐based devices for off‐site diagnosis and bioassays are also described to cover this emerging platform for low‐cost diagnostics.

Capacitively coupled contactless conductivity detection on microfluidic systems—ten years of development

The use of capacitively coupled contactless conductivity detection (C4D) on miniaturized systems has increased considerably over the last few years. Since the first report, 10 years ago, several advances on the detection cell geometry, strategies for increasing the sensitivity and a wide range of applications have been reported. This review intends to cover the main features related to the instrumental setup of this detection method for analytical and bioanalytical assays on microfluidic chips.

Recent advances in low-cost microfluidic platforms for diagnostic applications

The use of inexpensive materials and cost‐effective manufacturing processes for mass production of microfluidic devices is very attractive and has spurred a variety of approaches. Such devices are particularly suited for diagnostic applications in limited resource settings. This review describes the recent and remarkable advances in the use of low‐cost substrates for the development of microfluidic devices for diagnostics and clinical assays. Thus, a plethora of new and improved fabrication methods, designs, capabilities, detections, and applications of microfluidic devices fabricated with paper, plastic, and threads are covered.

Determination of Inorganic Ions in Ethanol Fuel by Capillary Electrophoresis

The control of the content of inorganic ions in vehicular fuels plays an important role in the engine maintenance. A novel and versatile methodology to carry out rapid analysis of ions in ethanol is presented. Capillary electrophoresis was used to quantify cations (sodium, potassium, calcium, magnesium, and ammonium) and anions (sulfate, chloride, and nitrate). The injection of the sample directly in the capillary shows some lack of repeatability of the results. The prior evaporation of the ethanol, followed by a re-suspension of the residual material, leads to reliable results. The detection limits of the eight ions range between 0.06 and 0.18 mg L-1. Lower detection limits could be attained by increasing the injection time and/or the injection pressure.

Instrumentation design for hydrodynamic sample injection in microchip electrophoresis: a review.

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.

Simultaneous determination of free fluoride and monofluorophosphate in toothpaste by capillary electrophoresis with capacitively coupled contactless conductivity detection.

Capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C(4)D) was used for rapid, accurate and simultaneous determination of free fluoride and monofluorophosphate (MFP) in six different toothpaste samples. A buffer solution containing 15 mmol L(-1) histine, 25 mmol L(-1) lactic acid, and 2.5 mmol L(-1) tetradecyltrimethylammonium bromide (TTAB) was used as background electrolyte (BGE). A complete separation of the analytes and the internal standard (tartrate) could be attained in less than 2.5 min. The limits of detection (LOD) and quantification (LOQ) were, respectively, 0.17 and 0.57 mg L(-1) for free fluoride and 0.70 and 2.33 mg L(-1) for MFP. Recoveries ranging from 85 to 107% were obtained for samples spiked with standard solutions of free fluoride or MFP. The CE-C(4)D method was compared to an ion-selective electrode (ISE) method and the results were in good agreement. More importantly, the CE-C(4)D method demonstrates the advantage of being able to determine MFP without a prior hydrolysis step.

Polyester‐toner electrophoresis microchips with improved analytical performance and extended lifetime

This paper reports the fabrication of polyester‐toner (PT) electrophoresis microchips with improved analytical performance and extended lifetime. This has been achieved with a better understanding about the EOF generation and the influence of some parameters including the channel dimensions (width and depth), the injection mode, and the addition of organic solvent to the running buffer. The analytical performance of the PT devices was investigated using a capacitively coupled contactless conductivity detector and inorganic cations as model analytes. The proposed devices have exhibited EOF values of (3.4 ± 0.2) × 10−4 cm2 V−1 s−1 with good stability over 25 consecutive runs. It has been found that the EOF magnitude depends on the channel dimension, i.e. the wider the channel, the higher the EOF value. The separation efficiency for inorganic cations ranged from 13 000 to 50 000 plates/m. The LOD found for K+, Na+, and Li+ were 4.2, 7.3, and 23 μM, respectively. In addition, the same PT device has been used by three consecutive days. Lately, due to improved analytical performance, it was carried out by the first time the detection of inorganic cations in real samples such as energetic drinks and pharmaceutical formulations.

Fast determination of ethambutol in pharmaceutical formulations using capillary electrophoresis with capacitively coupled contactless conductivity detection

A method for the determination of ethambutol (EMB), a first‐line drug against tuberculosis, based on CE with capacitively coupled contactless conductivity detection is proposed. The separation of EMB and its main product of degradation were achieved in less than 3 min with a resolution of 2.0 using a BGE composed of 50 mmol/L histidine and 30 mmol/L MES, pH 6.30. By raising the pH to 8.03, the analysis time was reduced to 1.0 min, but with a significant loss of resolution (0.7). Using the best separation conditions, linearity of 0.9976 (R2, five data points), sensitivity of 1.26×10−4 V min μmol−1 L, and LOD and quantification of 23.5 and 78.3 μmol/L, respectively, were obtained. Recoveries at four levels of concentration ranged from 95 to 102% and the concentration range studied ranged from 100 to 500 μmol/L. The results obtained for the determination of EMB in pharmaceutical formulations were compared with those obtained by using CE with photometric detection.

Microssistemas de análises químicas: introdução, tecnologias de fabricação, instrumentação e aplicações

The amazing world of micro total analysis systems has provided a true revolution in analytical chemistry in recent years. The application of the microfluidic devices for chemical and biochemical processing has attracted considerable interest due to its advantages such as reduced sample and reagent consumption, processing time, energy, waste, cost, and portability. The aim of the present report is to disseminate the state of the art related to the miniaturization science in Analytical Chemistry. Historical progress, microfabrication technologies, required instrumentation and applications of the mTAS are presented in the current article, with special attention to the Brazilian contributions.

Aplicações eletroanalíticas com eletrodos de prata confeccionados a partir de CDs graváveis

This paper presents a new way for the construction of silver electrodes utilizing recordable CDs. The new electrodes were explored for the quantification of chloride (by potentiometry/FIA), cyanide (by amperometry/FIA) and for lead analysis (by square wave voltammetry). For the flowing measurements, a digital multimeter, connected to a microcomputer (via RS 232 interface) was used to collect directly the potential signal (for Cl- measurements) or to take the output signal from a potentiostat (for CN- measurements). The square wave voltammetry analysis was performed in a commercial instrument. The results shown good performance of the new electrodes and the detection limit (s/n = 3) attained for these three analytes were: 0.2, 50, and 200 µg L-1 for Pb2+, Cl-, and CN- respectively.