Immobilization of Acetylcholinesterase on Screen-Printed Electrodes. Application to the Determination of Arsenic(III)

Enzymatic amperometric procedures for measuring arsenic, based on the inhibitive action of this metal on acetylcholinesterase enzyme activity, have been developed. Screen-printed carbon electrodes (SPCEs) were used with acetylcholinesterase covalently bonded directly to its surface. The amperometric response of acetylcholinesterase was affected by the presence of arsenic ions, which caused a decrease in the current intensity. The experimental optimum working conditions of pH, substrate concentration and potential applied, were established. Under these conditions, repeatability and reproducibility of biosensors were determined, reaching values below 4% in terms of relative standard deviation. The detection limit obtained for arsenic was 1.1 × 10−8 M for Ach/SPCE biosensor. Analysis of the possible effect of the presence of foreign ions in the solution was performed. The method was applied to determine levels of arsenic in spiked tap water samples.Junta de Castilla y León (BU022A07, Q0968272E) and the Ministerio de Ciencia e Innovación (TEC2008-01367/TEC) is gratefully acknowledged

4-ethyphenol detection in wine by fullerene modified screen-printed carbon electrodes

This work shows the potential of modified screen-printed carbon electrodes (SPCEs) for sensitive and selective detection of 4-ethylphenol in wine. Gold nanoparticles (AuNPs) and fullerene C60 (C60), modified sensors have been compared. pH of the supporting electrolyte, deposition time and working temperature have been optimized considering their influence in the voltammetric pulse response of 4-ethylphenol. Under the optimal conditions of measurement, the developed activated C60/SPCE (AC60/SPCE) shows the best performance, with a detection capability of 400 μg/L and 700 μg/L, when using deposition times of 14 min and 6 min, respectively (α = β = 0.05). The reproducibility of the developed sensor resulted better when a deposition time of 6 min was used (5.4 %, n = 3). The influence of different interferents on the analytical response has been studied, as well as their application in the determination of 4-ethylphenol in different wine samples.Authors would like to acknowledge funding obtained by Junta de Castilla y León (BU018G19) and Agencia Estatal de Investigación (PID2020-117095RB-I00)

Electrochemical devices for cholesterol detection

Cholesterol can be considered as a biomarker of illnesses such as heart and coronary artery diseases or arteriosclerosis. Therefore, the fast determination of its concentration in blood is interesting as a means of achieving an early diagnosis of these unhealthy conditions. Electrochemical sensors and biosensors have become a potential tool for selective and sensitive detection of this biomolecule, combining the analytical advantages of electrochemical techniques with the selective recognition features of modified electrodes. This review covers the different approaches carried out in the development of electrochemical sensors for cholesterol, differentiating between enzymatic biosensors and non-enzymatic systems, highlighting lab-on-a-chip devices. A description of the different modification procedures of the working electrode has been included and the role of the different functional materials used has been discussed

Determination of aluminium using different techniques based on the Al(III)-morin complex

Three different methods for the determination of Al(III) in aqueous samples were compared. The different described procedures were based on the formation of the Al(III)-morin complex. UV–Vis spectrophotometry, spectrofluorimetry and differential pulse adsorptive stripping voltammetry (DPAdSV) techniques were compared under optimized experimental conditions. The DPAdSV method showed a better performance for the analysis of Al(III) in terms of capability of detection (70 nM) in comparison with the value obtained for UV–Vis spectrophotometric (300 nM) and spectrofluorimetic (110 nM) techniques. Thus, DPAdSV method was selected for the analysis of aluminium in river, tap and bottled water samples under the following optimized experimental conditions: pH = 4.4, deposition potential = +243 mV, deposition time = 210 s, giving satisfactory results

A Disposable Alkaline Phosphatase-Based Biosensor for Vanadium Chronoamperometric Determination

A chronoamperometric method for vanadium ion determination, based on the inhibition of the enzyme alkaline phosphatase, is reported. Screen-printed carbon electrodes modified with gold nanoparticles were used as transducers for the immobilization of the enzyme. The enzymatic activity over 4-nitrophenyl phosphate sodium salt is affected by vanadium ions, which results in a decrease in the chronoamperometric current registered. The developed method has a detection limit of 0.39 ± 0.06 µM, a repeatability of 7.7% (n = 4) and a reproducibility of 8% (n = 3). A study of the possible interferences shows that the presence of Mo(VI), Cr(III), Ca(II) and W(VI), may affect vanadium determination at concentration higher than 1.0 mM. The method was successfully applied to the determination of vanadium in spiked tap waterResearch Vicerrectory of Costa Rica University (Project 804-B0-058) and Spanish Ministry of Science and Innovation (TEC-2009/12029). This work was supported by the Spanish Ministry of Science and Innovation (MICINN) 410 and the European Regional Development Fund (FEDER) (INNPACTO SERIBIO 2011-411 2014) and TEC2009-12029, as well as through Junta de Castilla y León (BU212A12-2)

A Chronoamperometric Screen Printed Carbon Biosensor Based on Alkaline Phosphatase Inhibition for W(VI) Determination in Water, Using 2-Phospho-L-Ascorbic Acid Trisodium Salt as a Substrate

This paper presents a chronoamperometric method to determine tungsten in water using screen-printed carbon electrodes modified with gold nanoparticles and cross linked alkaline phosphatase immobilized in the working electrode. Enzymatic activity over 2-phospho-L-ascorbic acid trisodium salt, used as substrate, was affected by tungsten ions, which resulted in a decrease of chronoamperometric current, when a potential of 200 mV was applied on 10 mM of substrate in a Tris HCl buffer pH 8.00 and 0.36 M of KCl. Calibration curves for the electrochemical method validation, give a reproducibility of 5.2% (n = 3), a repeatability of 9.4% (n = 3) and a detection limit of 0.29 ± 0.01 μM. Enriched tap water, purified laboratory water and bottled drinking water, with a certified tungsten reference solution traceable to NIST, gave a recovery of 97.1%, 99.1% and 99.1% respectively (n = 4 in each case) and a dynamic range from 0.6 to 30 μM. This study was performed by means of a Lineweaver–Burk plot, showing a mixed kinetic inhibition.Vicerrectorìa de Investigación de la Universidad de Costa Rica (Project 804-B2-297), via Junta de Castilla y León (BU212A12-2), Ministerio de Ciencia e Innovación (MICINN) (TEC2009-12029) and MICINN and Fondo Europeo de Desarrollo Regional (FEDER) (INNPACTO SERIBIO 2011-2014)

Determination of Antimony (III) in Real Samples by Anodic Stripping Voltammetry Using a Mercury Film Screen-Printed Electrode

This paper describes a procedure for the determination of antimony (III) by differential pulse anodic stripping voltammetry using a mercury film screen-printed electrode as the working electrode. The procedure has been optimized using experimental design methodology. Under these conditions, in terms of Residual Standard Deviation (RSD), the repeatability (3.81 %) and the reproducibility (5.07 %) of the constructed electrodes were both analyzed. The detection limit for Sb (III) was calculated at a value of 1.27×10−8 M. The linear range obtained was between 0.99 × 10−8 − 8.26 × 10−8 M. An analysis of possible effects due to the presence of foreign ions in the solution was performed and the procedure was successfully applied to the determination of antimony levels in pharmaceutical preparations and sea water samples

Molecularly imprinted polypyrrole based electrochemical sensor for selective determination of 4-ethylphenol

This work describes the development of an electrochemical sensor based on a molecularly imprinted polymer (MIP) for sensitive and selective determination of 4-ethylphenol in wine. The sensor has been built by means of the electrosynthesis of the MIP on a glassy carbon electrode surface using cyclic voltammetry. The electropolymerization has been performed in the presence of 4-ethylphenol and pyrrole as template molecule and functional monomer, respectively. The influence of the molar ratios of template molecules to functional pyrrole monomers and the time needed to remove the template have been optimized taking into account the differential pulse voltammetric response of 4-ethylphenol. Under the optimal experimental conditions the developed MIP/GCE sensor shows good capability of detection (0.2 μM, α = β = 0.05) and reproducibility (3.0%) in the concentration range from 0.2 to 34.8 μM. The influence of possible interfering species in the analytical response has been studied and the sensor has successfully been applied to the determination of 4-ethylphenol in different wine samples.Junta de Castilla y León (BU018G19