Desarrollo de un electrodo selectivo basado en polipirrol para la determinación de iones citratos en bebidas no alcohólicas

En la industria alimentaria, uno de los aditivos más empleado es el ácido cítrico, el cual se añade principalmente a las bebidas en forma de sales de citrato, debido a su poder acidulante y conservador. A pesar de considerarse un aditivo de uso seguro, es necesario contar con métodos que permitan su cuantificación para cumplir la dosis máxima señalada en las normas, generalmente se emplea HPLC; sin embargo, presenta ciertas desventajas como el pretratamiento de la muestra. Por ello, una alternativa viable para la cuantificación de citratos es el uso de la potenciometría a través de emplear electrodos selectivos a iones, ya que son sensibles, selectivos y presentan límites de detección y cuantificación bajos. Aprovechando las ventajas de estos sensores, se presenta en este trabajo el desarrollo de un electrodo selectivo a iones, el cual se modificó empleando polipirrol dopado con iones citrato (Ppy- Citrato), el electrodo presentó los siguientes parámetros analíticos: límite de detección 1.17x10-⁵ M y una sensibilidad de -45.08 mV/ década [citrato].In food industry, citric acid is used as additive due to its properties as acidulant and its conservative power. It is mainly added to beverages in the form of citrate salts. Despite it is considered a safe additive, it becomes necessary to develop methods that allow its quantification in order to accomplish the reported standards in food, generally HPLC is used as official quantification method; however, this technique presents certain disadvantages as the pre-treatment of the sample. Therefore, a viable alternative for the quantification of citrates is potentiometry with the use of ion-selective electrodes, because they are sensitive, selective and present low detection and quantification limits. Taking advantage of these sensors, in this paper we present the development of a selective electrode to citrates, which is based in the modificated electrode using doped polypyrrol with citrate ions, (Ppy-citrate). The so developed electrode presents the following analytical parameters: detection limit 1.17 x 10-⁵ M and a sensitivity of -45.08 mV / decade [citrate

Optimización del método de cuantificación voltamperométrico de naproxeno usando un electrodo de pasta de carbono

En el presente trabajo se describe un método sencillo para la cuantificación voltamperométrica de naproxeno. La oxidación del naproxeno se llevó a cabo en dos diferentes electrodos de pasta de carbono con y sin nanotubos de carbono (NTC), utilizando voltamperometría diferencial de pulsos para su cuantificación. Se observa un pico de oxidación a un potencial de 0.916 V y 0.940 V respectivamente contra un electrodo de referencia Ag/AgCl saturado, en un buffer de fosfatos 0.1 molL-¹ a pH 7. El proceso de oxidación del naproxeno está regido por la difusión en los dos diferentes electrodos de trabajo y es un proceso irreversible. Se realiza una curva de calibración para cada electrodo de trabajo donde se obtienen los parámetros analíticos donde los mejores resultan para el electrodo grafito-NTC con un coeficiente de correlación de 0.993, una sensibilidad 2.2±0.1 μA/μmolL-¹, un LD y LC de 0.1 y 0.33 μmolL-¹ respectivamente. El método propuesto es una alternativa para la cuantificación de naproxeno en muestras farmacéuticas.The present work describes a simple method for the voltammetric quantification of naproxen. Oxidation of naproxen was performed using two different carbon paste electrodes, with and without carbon nanotubes (CNT) using differential pulse voltammetry for quantification. A maximum anodic current was recorded at a 0.916 V and 0.940 V, referred to a saturated Ag/AgCl reference electrode, in the presence of 0.1 molL-1 phosphates buffer at pH 7. Naproxen’s oxidation is an irreversible diffusion-controlled process for the two different working electrodes. Calibration curves were obtained for each working electrode where the best analytical parameters are obtained using the graphite-CNT electrode with a correlation coefficient of 0.993, sensitivity of 2.2 ± 0.1 μA/μmolL1, detection and quantification limits of 0.1 and 0.33 μmolL-1 respectively. The method proposed was adequate for naproxen quantification in pharmaceutical samples

Earliest Results in the Use of Activated Composite Membranes for the Transport of Silver Ions from Aqueous Solutions

This paper presents the results concerning the first use of activated composite membranes (ACMs) for the facilitated transport of silver ions containing di-(2-ethylhexyl)-dithiophosphoric acid (DTPA) as the carrier. DTPA was immobilized by interfacial polymerization in a dense layer that was deposited in a porous layer, which was prepared on a nonwoven fabric support by phase inversion. The influence of fundamental parameters affecting the transport of silver ion as the carrier concentration in the membrane phase and stripping agent variation of the stripping solution have been studied. In the optimal conditions, the amount of silver transported across the ACMs was greater than 50%, whereas if the content of the carrier is modified, more than the 90% of the initial silver is removed from the feed phase

Desarrollo de una metodología voltamperométrica para la determinación de Aflatoxina B1 usando un electrodo de carbón vítreo modificado con una película de bismuto y nanopartículas de oro

La Aflatoxina B1 es una micotoxina altamente cancerígena que se encuentra en una gran variedad de alimentos y piensos, por lo tanto, su cuantificación es importante para la industria de los alimentos. En este trabajo de investigación se describe el desarrollo de una metodología electroanalítica utilizando un electrodo de carbón vítreo modificado superficialmente con una película de bismuto y nanopartículas de oro para la cuantificación de Aflatoxina B1, por las ventajas que presenta frente a otras metodologías que ya se han estudiado y validado para la cuantificación de esta sustancia. Los límites de detección y de cuantificación que se obtuvieron después de la de la optimización de la Voltamperometría de Onda Cuadrada mediante un diseño Box-Behnken fueron 11.19 y 37.31 ng L-¹, respectivamente. Estos parámetros nos indican que es posible cuantificar la aflatoxina B1 en un intervalo de concentraciones a nivel traza, tal como se encuentra en alimentos.feeds, therefore, its quantification is important for the food industry. This research paper describes the development of an electroanalytical methodology using a glassy carbon electrode modified with a bismuth film and gold nanoparticles for quantification of Aflatoxin B1, due to the advantages it presents over other methodologies that have already been studied and validated for the quantification of this substance. The detection and quantification limits obtained after optimization of Square Wave Voltammetry using a Box-Behnken design were 11.19 and 37.31 ng L-¹, respectively. These parameters indicated that it is possible to quantify the Aflatoxin B1 in a wide concentration range at trace levels, as expected in food

Cuantificación y caracterización electroquímica de diclofenaco en electrodo de grafito

En el presente trabajo se propone una metodología nueva para detectar y cuantificar diclofenaco. La cuantificación se hace de manera indirecta se realiza en medio acuoso con una barra de grafito como electrodo de trabajo. Se analiza el proceso electroquímico del diclofenaco a través de una voltamperometría cíclica encontrando dos picos anódicas a un potencial de 0.60 V y 0.92 V; en sentido catódico dos pico a 0.057 V y 0.343 V. Para generar la señal analítica se usan dos tratamientos diferentes: un tratamiento potenciométrico y otro potenciostático. La metodología propuesta se usa para la cuantificación de diclofenaco en muestras farmacéuticas comerciales, resultando un método correlativo.In this work, a new method is proposed for sensing diclofenac. Indirect quantification is performed in aqueous media with a graphite bar as working electrode. The electrochemical process is analyzed using cyclic voltammetry and two anodic peaks are found at 0.60 V and 0.92 V, also two cathodic peaks at 057 V and 0.343 V. To generate the analytic signal, two different treatments are studied: potentiodynamic and potentiostatic to the working electrode. The proposed methodology is used for diclofenac quantification in commercial pharmaceutical samples, resulting a competitive method

Point-of-Care Sensors in Clinical Environments

Thanks to a general multidisciplinary and interdisciplinary approach, during the last few decades there have been huge advances in the diagnostic field. In particular, the miniaturization and automation of several assays have led to the development of the so-called point-of-care tests (PoCT), which are devices capable to provide accurate and specific detection of analytes such as glucose, other clinically-relevant biomarkers, pathogens, and drugs. The detection with these devices typically takes place in a few minutes and without the need of specialized personnel. Here we discuss the key technologies and applications of PoCTs, as well as the major challenges in the clinical environment.Peer reviewe

Simultaneous Quantification of Four Principal NSAIDs through Voltammetry and Artificial Neural Networks Using a Modified Carbon Paste Electrode in Pharmaceutical Samples

This work describes the development of a novel and low-cost methodology for the simultaneous quantification of four main nonsteroidal anti-inflammatory drugs (NSAIDs) in pharmaceutical samples using differential pulse voltammetry coupled with an artificial neural network model (ANN). The working electrode used as a detector was a carbon paste electrode (CPE) modified with multi-wall carbon nanotubes (MWCNT-CPE). The specific voltammetric determination of the drugs was performed by cyclic voltammetry (CV). Some characteristic anodic peaks were found at potentials of 0.446, 0.629, 0.883 V related to paracetamol, diclofenac, and aspirin. For naproxen, two anodic peaks were found at 0.888 and 1.14 V and for ibuprofen, an anodic peak was not observed at an optimum pH of 10 in 0.1 mol L−1 Britton–Robinson buffer. Since these drug’s oxidation process turned out to be irreversible and diffusion-controlled, drug quantification was carried out by differential pulse voltammetry (DPV). The Box Behnken design technique’s optimal parameters were: step potential of 5.85 mV, the amplitude of 50 mV, period of 750 ms, and a pulse width of 50 ms. A data pretreatment was carried out using the Discrete Wavelet Transform using the db4 wavelet at the fourth decomposition level applied to the voltammetric records obtained. An ANN was built to interpret the obtained approximation coefficients of voltammograms generated at different drug concentrations to calibrate the system. The ANN model’s architecture is based on a Multilayer Perceptron Network (MLP) that employed a Bayesian regularization training algorithm. The trained MLP achieves significant R values for the test data to simultaneous quantification of the four drugs in the presence of aspirin

Simultaneous Voltammetric Determination of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) Using a Modified Carbon Paste Electrode and Chemometrics

This work presents the simultaneous quantification of four non-steroidal anti-inflammatory drugs (NSAIDs), paracetamol, diclofenac, naproxen, and aspirin, in mixture solutions, by a laboratory-made working electrode based on carbon paste modified with multi-wall carbon nanotubes (MWCNT-CPE) and Differential Pulse Voltammetry (DPV). Preliminary electrochemical analysis was performed using cyclic voltammetry, and the sensor morphology was studied by scanning electronic microscopy and electrochemical impedance spectroscopy. The sample set ranging from 0.5 to 80 µmol L−1 was prepared using a complete factorial design (34) and considering some interferent species such as ascorbic acid, glucose, and sodium dodecyl sulfate to build the response model and an external randomly subset of samples within the experimental domain. A data compression strategy based on discrete wavelet transform was applied to handle voltammograms’ complexity and high dimensionality. Afterward, Partial Least Square Regression (PLS) and Artificial Neural Networks (ANN) predicted the drug concentrations in the mixtures. PLS-adjusted models (n = 12) successfully predicted the concentration of paracetamol and diclofenac, achieving correlation values of R ≥ 0.9 (testing set). Meanwhile, the ANN model (four layers) obtained good prediction results, exhibiting R ≥ 0.968 for the four analyzed drugs (testing stage). Thus, an MWCNT-CPE electrode can be successfully used as a potential sensor for voltammetric determination and NSAID analysis

Earliest Results in the Use of Activated Composite Membranes for the Transport of Silver Ions from Aqueous Solutions

This paper presents the results concerning the first use of activated composite membranes (ACMs) for the facilitated transport of silver ions containing di-(2-ethylhexyl)-dithiophosphoric acid (DTPA) as the carrier. DTPA was immobilized by interfacial polymerization in a dense layer that was deposited in a porous layer, which was prepared on a nonwoven fabric support by phase inversion. The influence of fundamental parameters affecting the transport of silver ion as the carrier concentration in the membrane phase and stripping agent variation of the stripping solution have been studied. In the optimal conditions, the amount of silver transported across the ACMs was greater than 50%, whereas if the content of the carrier is modified, more than the 90% of the initial silver is removed from the feed phase

Recent Advances in the Use of Transition-Metal Porphyrin and Phthalocyanine Complexes as Electro-Catalyst Materials on Modified Electrodes for Electroanalytical Sensing Applications

Metalloporphyrins (MP) and metallophtalocyanines (MPc) are innovative materials with catalytic properties that have attracted attention for their application for diverse electrochemical purposes. The presence of metallic centers in their structure offers a redox-active behavior that is being applied in the design of solid electrodes for the quantification of biomolecules, water contaminants, and pharmaceuticals, among others. Herein, we collect the recent information about porphyrin and phthalocyanine complexes as modifiers of electrodes, and the important aspects of the design, characterization, and application of these electrodes