Eduardo Garcia-Breijo

Freshness monitoring of sea bream (Sparus aurata) with a potentiometric sensor

Freshness in one of the main quality attributes for fish commercialization and consumption. The traditional method for fish freshness evaluation is sensory analysis. However, instrumental methods such as electrical, texture and colour measurements, image analysis, VIS spectroscopy and electronic noses have been widely studied as objective alternatives. Each of these methods has advantages and disadvantages, but none of them can be universally proposed for defining and measuring fish freshness. This work evaluated the correlation of potentiometric measurements, obtained with gold and silver electrodes, with physicochemical, microbiological and biochemical analyses of sea bream stored under refrigeration. Results showed a strong correlation of the potentiometric measurements with the determined changes in fish, and an important correlation with the K1 index, dependent on the nucleoside degradation, which is used as a good indicator of post-mortem time and freshness.

Active flexible concentric ring electrode for non-invasive surface bioelectrical recordings

Bioelectrical surface recordings are usually performed by unipolar or bipolar disc electrodes even though they entail the serious disadvantage of having poor spatial resolution. Concentric ring electrodes give improved spatial resolution, although this type of electrode has so far only been implemented in rigid substrates and as they are not adapted to the curvature of the recording surface may provide discomfort to the patient. Moreover, the signals recorded by these electrodes are usually lower in amplitude than conventional disc electrodes. The aim of this work was thus to develop and test a new modular active sensor made up of concentric ring electrodes printed on a flexible substrate by thick-film technology together with a reusable battery-powered signal-conditioning circuit. Simultaneous ECG recording with both flexible and rigid concentric ring electrodes was carried out on ten healthy volunteers at rest and in motion. The results show that flexible concentric ring electrodes not only present lower skin–electrode contact impedance and lower baseline wander than rigid electrodes but are also less sensitive to interference and motion artefacts. We believe these electrodes, which allow bioelectric signals to be acquired non-invasively with better spatial resolution than conventional disc electrodes, to be a step forward in the development of new monitoring systems based on Laplacian potential recordings.

Low-Cost Capacitive Humidity Sensor for Application Within Flexible RFID Labels Based on Microcontroller Systems

This paper reports on the fabrication of a capacitive-type relative humidity (RH) sensor using screen printing processes for electrode film deposition. The applied measurement method based on microcontrollers is also reported. In this specific case, the microcontroller is used to measure RH by means of a capacitive sensor with a simple low-cost electronic system. In addition, a comparison between two different types of polyester substrates [Melinex (DuPont) and CG3460 (3M)] is shown. Both polyester substrates have similar properties, and only the thickness is different (175 μm for Melinex and 100 μm for CG3460). A nonlineal response has been obtained in this type of sensors. In order to linearize the response and reduce the external hardware, an artificial neural network embedded into the microcontroller has been used.

An investigation into the effect of fabrication parameter variation on the characteristics of screen‐printed thick‐film silver/silver chloride reference electrodes

Purpose – The purpose of this paper is to show how the fabrication parameters of screen‐printed thick‐film reference electrodes have been experimentally varied and their effect on device characteristics investigated.Design/methodology/approach – The tested devices were fabricated as screen‐printed planar structures consisting of a silver back contact, a silver/silver chloride interfacial layer and a final salt reservoir layer containing potassium chloride. The fabrication parameters varied included deposition method and thickness, salt concentration and binder type used for the final salt reservoir layer. Characterisation was achieved by monitoring the electrode potentials as a function of time following initial immersion in test fluids in order to ascertain initial hydration times, subsequent electrode drift rates and useful lifetime of the electrodes. Additionally, the effect of fabrication parameter variation on electrode stability and their response time in various test media was also investigated.Fin...

An Embedded Simplified Fuzzy ARTMAP Implemented on a Microcontroller for Food Classification

In the present study, a portable system based on a microcontroller has been developed to classify different kinds of honeys. In order to do this classification, a Simplified Fuzzy ARTMAP network (SFA) implemented in a microcontroller has been used. Due to memory limits when working with microcontrollers, it is necessary to optimize the use of both program and data memory. Thus, a Graphical User Interface (GUI) for MATLAB® has been developed in order to optimize the necessary parameters to programme the SFA in a microcontroller. The measures have been carried out by potentiometric techniques using a multielectrode made of seven different metals. Next, the neural network has been trained on a PC by means of the GUI in Matlab using the data obtained in the experimental phase. The microcontroller has been programmed with the obtained parameters and then, new samples have been analysed using the portable system in order to test the model. Results are very promising, as an 87.5% recognition rate has been achieved in the training phase, which suggests that this kind of procedures can be successfully used not only for honey classification, but also for many other kinds of food.

Glyphosate Detection by Means of a Voltammetric Electronic Tongue and Discrimination of Potential Interferents

A new electronic tongue to monitor the presence of glyphosate (a non-selective systemic herbicide) has been developed. It is based on pulse voltammetry and consists in an array of three working electrodes (Pt, Co and Cu) encapsulated on a methacrylate cylinder. The electrochemical response of the sensing array was characteristic of the presence of glyphosate in buffered water (phosphate buffer 0.1 mol·dm−3, pH 6.7). Rotating disc electrode (RDE) studies were carried out with Pt, Co and Cu electrodes in water at room temperature and at pH 6.7 using 0.1 mol·dm−3 of phosphate as a buffer. In the presence of glyphosate, the corrosion current of the Cu and Co electrodes increased significantly, probably due to the formation of Cu2+ or Co2+ complexes. The pulse array waveform for the voltammetric tongue was designed by taking into account some of the redox processes observed in the electrochemical studies. The PCA statistical analysis required four dimensions to explain 95% of variance. Moreover, a two-dimensional representation of the two principal components differentiated the water mixtures containing glyphosate. Furthermore, the PLS statistical analyses allowed the creation of a model to correlate the electrochemical response of the electrodes with glyphosate concentrations, even in the presence of potential interferents such as humic acids and Ca2+. The system offers a PLS prediction model for glyphosate detection with values of 098, −2.3 × 10−5 and 0.94 for the slope, the intercept and the regression coefficient, respectively, which is in agreement with the good fit between the predicted and measured concentrations. The results suggest the feasibility of this system to help develop electronic tongues for glyphosate detection.

Low-Cost Electronic Tongue System and Its Application to Explosive Detection

The use of biomimetic measurement systems as electronic tongues and noses has considerably increased in the last years. This paper presents the design of a low-cost electronic tongue system that includes a software application that runs on a personal computer and electronic equipment based on a 16-b microcontroller. The designed system is able to implement voltammetry and impedance spectroscopy measurements with different-electrode configurations. The data obtained from the electrochemical measurements can be used to build statistical models able to assess physicochemical properties of the samples. The designed system has been applied to the detection and quantification of trinitrotoluene (TNT), which is one of the most common explosive materials. Pulse voltammetry measurements were carried out on TNT samples with different concentration levels. The principal component analysis of the obtained results shows that the electronic tongue is able to detect TNT in acetonitrile samples. Prediction models were built with partial least squares regression, and a good correlation was observed between the pulse voltammetry measurements and the TNT concentration levels. In this experience, a new voltammetric data compression algorithm based on polynomial approximations has been tested with good results. The electronic tongue has also been applied to the prediction of water quality parameters in wastewater and to the evaluation of different-pulse array designs for pulse voltammetry experiences.

An Electrochemical Impedance Spectroscopy-Based Technique to Identify and Quantify Fermentable Sugars in Pineapple Waste Valorization for Bioethanol Production

Electrochemical Impedance Spectroscopy (EIS) has been used to develop a methodology able to identify and quantify fermentable sugars present in the enzymatic hydrolysis phase of second-generation bioethanol production from pineapple waste. Thus, a low-cost non-destructive system consisting of a stainless double needle electrode associated to an electronic equipment that allows the implementation of EIS was developed. In order to validate the system, different concentrations of glucose, fructose and sucrose were added to the pineapple waste and analyzed both individually and in combination. Next, statistical data treatment enabled the design of specific Artificial Neural Networks-based mathematical models for each one of the studied sugars and their respective combinations. The obtained prediction models are robust and reliable and they are considered statistically valid (CCR% > 93.443%). These results allow us to introduce this EIS-based technique as an easy, fast, non-destructive, and in-situ alternative to the traditional laboratory methods for enzymatic hydrolysis monitoring.

An electronic tongue for monitoring drinking waters using a fuzzy ARTMAP neural network implemented on a microcontroller

A portable electronic tongue has been developed using an array of eighteen thick-film electrodes of different materials forming a multi-electrode array. A microcontroller is used to implement the pattern recognition. The classification of drinking waters is carried out by a Microchip PIC18F4550 microcontroller and is based on a fuzzy ARTMAP neural network algorithm. This algorithm is initially trained with the multi-electrode array on a Personal Computer (PC) using several samples of waters (still, sparkling and tap) to obtain the optimum architecture with the weights and the map field of the network. Once it is trained, the computed weights and map field are programmed into the microcontroller, which then gives the water classification directly for new unknown water samples.

Analysis of Fish Freshness by Using Metallic Potentiometric Electrodes

We report herein the development of a simple electronic system that uses simple potentiometric electrodes applied to the analysis fish freshness. The array of sensors is built by using metallic electrodes as plain sharp wires or in a thick-film configuration. Experiments on real fish led to the conclusion that gold and silver electrodes are suitable for the development of qualitative systems able to classify fish in relation to its freshness. Equipment based on a microprocessors programmed with fuzzy logic can be developed for in situ monitorization of fish quality.