Microfluidic devices are an interesting alternative for performing analytical assays, due to the speed of analyses, reduced sample, reagent and solvent consumption and less waste generation. However, the high manufacturing costs still prevent the massive use of these devices worldwide. Here, we present the construction of a low cost microfluidic thread-based electroanalytical device (μTED), employing extremely cheap materials and a manufacturing process free of equipment. The microfluidic channels were built with cotton threads and the estimated cost per device was only $0.39. The flow of solutions (1.12 μL s(-1)) is generated spontaneously due to the capillary forces, eliminating the use of any pumping system. To demonstrate the analytical performance of the μTED, a simultaneous determination of acetaminophen (ACT) and diclofenac (DCF) was performed by multiple pulse amperometry (MPA). A linear dynamic range (LDR) of 10 to 320 μmol L(-1) for both species, a limit of detection (LOD) and a limit of quantitation (LOQ) of 1.4 and 4.7 μmol L(-1) and 2.5 and 8.3 μmol L(-1) for ACT and DCF, respectively, as well as an analytical frequency of 45 injections per hour were reached. Thus, the proposed device has shown potential to extend the use of microfluidic analytical devices, due to its simplicity, low cost and good analytical performance.

Microfluidic devices constructed using low cost materials presents as alternative for conventional flow analysis systems because they provide advantages as low consumption of reagents and samples, high speed of analysis, possibility of portability and the easiness of construction and maintenance. Herein, is described for the first time the use of an electrochemical biosensor for phenol detection combined with a very simple and efficient microfluidic device based on commercial textile threads. Taking advantages of capillary phenomena and gravity forces, the solution transportation is promoted without any external forces or injection pump. Screen printed electrodes were modified with carbon nanotubes/gold nanoparticles followed by covalent binding of tyrosinase. After the biosensor electrochemical characterization by cyclic voltammetry technique, the optimization of relevant parameters such as pH, potential of detection and linear range for the biosensor performance was carried out; the system was evaluated for analytical phenol detection presenting limit of detection and limit of quantification 2.94nmolL and 8.92nmolL respectively. The proposed system was applied on phenol addition and recovery studies in drinking water, obtaining recoveries rates between 90% and 110%.

Microflow systems are powerful analytical tools that explore similar principles of typical flow injection analysis driven to in a microfluidic device. Generally, microfluidic devices can promote a low consumption of reagents and samples, high speed of analysis and possibility of portability. Several advances have been reached applying a simple and low cost device based on cotton thread as microfluidic channel where the transportation of solutions is based on capillary force helped by gravity. In the present work, we have demonstrated the versatility of thread-based electroanalytical devices (μTED) constructed using a cotton thread as the solution channel and screen-printed electrodes (SPE) surface modified with carbon nanotubes (CNT) as electrochemical detectors for the amperometric determination of estriol hormone in pharmaceutical samples. The parameters involved in the amperometric detection and microflow system were studied and optimized, using the best experimental conditions (flow rate of 0.50 μL s−1, 10 mm of analytical path, 2.0 μL of volume of injection and potential of detection of 0.75 V) a linear response was observed for concentration range (LDR) of 1.0 to 1000 μmol L−1 with limits of detection (LOD) and quantification (LOQ) of 0.53 μmolL−1 and 1.77 μmolL−1, respectively, and frequency of injection of 32 per hour. The proposed methodology was applied for determination of estriol in commercial samples and results were compared with those provided by spectrophotometric method (official methodology). The obtained results are in agreement at a 95% of confidence level.

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