Carbon-based Screen-printed Electrodes Research Articles

Enhanced voltammetric determination of metal ions by using a bismuthene-modified screen-printed electrode

• Bismuthene modified screen-printed carbon electrode (2D bi exf -SPCE) is proposed for the determination of Pb(II) and Cd(II) metal ions by DPASV. • Exfoliated layered bismuth (2D Bi exf ) was easily attached on SPCE by drop-casting. • Improved sensitivities and LODs are achieved when using 2D bi exf -SPCE instead of Bare-SPCE, BiNP-SPCE and bi sp SPE. • Reliable and very high reproducibility in the analysis of a certified estuarine water reference material. A new bismuthene carbon-based screen-printed electrode (2D Bi exf –SPCE) was easily prepared, taking advantage of the strongest features of exfoliated layered bismuth (bismuthene) for metal ions detection by differential pulse anodic stripping voltammetry (DPASV). An exfoliated bismuth suspension was drop-casted on the working electrode surface of a screen-printed carbon electrode (SPCE), giving rise to the 2D Bi exf –SPCE. It was microscopically and analytically examined and compared not only with bare SPCE but also with other bismuth-based screen-printed sensors that report good analytical performance, i.e., bismuth nanoparticle-modified SPCE (BiNP-SPCE) and sputtered bismuth SPE (Bi sp SPE). Under improved conditions and for a 120 s preconcentration time, the sensor exhibits good correlation between peak area and metal concentration in the range 0.2–25.0 μg L −1 for both Pb(II) and Cd(II) with LODs (3 times the standard deviation of the intercept over the slope of the linear calibration curve) of 0.06 and 0.07 μg L −1 for Pb(II) and Cd(II), respectively. 2D Bi exf –SPCE has been successfully applied to a certified estuarine water reference material with excellent trueness and remarkable reproducibility.

Cost Effective Soil pH Sensor Using Carbon-Based Screen-Printed Electrodes

This paper for the first time demonstrates a low cost, easy to make, disposable and paper-based soil pH sensor. The measurement of soil pH is performed using three electrode based electrochemical platform. The sensor is printed using screen-printing technique on a non-tearable hydrophobic paper. Carbon paste is modified with pH sensitive quinone moiety, alizarin, which shows 2e−/2H+ redox process. The detection is carried out using square wave voltammetry at 25 ± 1°C. Eleven different kinds of soil have been collected from three different provinces in India. Samples are prepared using the standard protocol viz . 1M KCl and 0.01M CaCl2. The sensitivity is 60.61 mV/pH and 65.16 mV/pH for buffer solution containing 1M KCl and 0.01M CaCl2, respectively. Two consecutive scans are taken for accurately measuring the soil pH. The first scan shows two peaks which correspond to different types of redox behaviour of alizarin. The second scan shows the actual pH behavior which is demonstrated for the first time. Soil samples prepared using KCl solution show the relative error within 4.9%. For CaCl2 samples the relative error is within 2.9% for soil pH less than 7.3 and within 7.9% for pH greater than 7.3.

Novel DNA Biosensor for Direct Determination of Carrageenan

A novel disposable electrochemical biosensor based on immobilized calf thymus double-stranded DNA (dsDNA) on the carbon-based screen-printed electrode (SPE) is developed for rapid biorecognition of carrageenan by using methylene blue (MB) redox indicator. The biosensor protocol for the detection of carrageenan is based on the concept of competitive binding of positively charged MB to the negatively charged dsDNA and carrageenan. The decrement in the MB cathodic peak current (ipc) signal as a result of the released MB from the immobilized dsDNA, and attracted to the carrageenan can be monitored via differential pulse voltammetry (DPV). The biosensor showed high sensitivity and selectivity to carrageenan at low concentration without interference from other polyanions such as alginate, gum arabic and starch. Calibration of the biosensor with carrageenan exhibited an excellent linear dependence from 1–10 mg L−1 (R2 = 0.98) with a detection limit of 0.08 mg L−1. The DNA-based carrageenan biosensor showed satisfactory reproducibility with 5.6–6.9% (n = 3) relative standard deviations (RSD), and possessing several advantages such as simplicity, fast and direct application to real sample analysis without any prior extensive sample treatments, particularly for seaweeds and food analyses.

First application of carbon-based screen-printed electrodes for the voltammetric determination of the organic UV filters oxybenzone and octocrylene

A new voltammetric methodology is proposed for the simultaneous determination of the organic UV filters oxybenzone (benzophenone 3, BP3) and octocrylene (OC) in personal care products and in wastewater extracts. It is based on previous adsorptive stripping voltammetric (AdSV) methods developed for hanging mercury drop electrodes, adapted to the special characteristics of carbon-based screen-printed electrodes. Among the carbon substrates tested, regular carbon screen-printed devices exhibited the best performance, with detection limits of 4.8 and 6.6 μmol L−1 and linearity ranges of 16–400 and 22–400 μmol L−1 for BP3 and OC, respectively, and, as compared to mercury electrodes, with the advantages of environmental safety, easy of use, low cost and compatibility with automation and flow measurements. The methodology has been successfully tested in real samples and compared to the standard methodology by liquid chromatography – tandem mass spectrometry (LC-MS/MS).

Preparation of V2O5/GOx onto a Screen-Printed Electrode for Sensing Surface of Glucose

Glucose oxidase (GOx) was immobilized on vanadium pentoxide xerogel (V2O5) onto a carbon-based screen-printed electrode to evaluate the possibility of constructing a V2O5/GOx biosensor. Structural characterizations of V2O5/GOx demonstrated a weak interaction between the species. Cyclic voltammetry results for V2O5/GOx after immobilization in 4.4 mmol/L of glucose, pH 5, in PBS medium indicated a stability tendency after several cycles and also an increase of total charge. The use of an electrochemical quartz crystal microbalance technique evidenced a mass loss after several cycles. Experimental studies using variations of glucose concentration and electrical characterization by extended gate field effect transistors is also discussed.

Mucin 4 detection with a label-free electrochemical immunosensor

Mucin 4 (MUC4) is a useful biomarker for endometriosis and cancers of the pancreas, esophagus and breast. The very first electrochemical immunosensor for the detection of MUC4 is reported, using carbon-based screen-printed electrodes modified by reaction with the diazonium salt of p-aminophenylacetic acid. Electrochemical impedance spectroscopy and cyclic voltammetry were used to characterize and optimize the electrografting process. The in situ surface modification through diazotation with phenylacetic groups enables the chemical binding of the specific antibody, followed by its affinity reaction with MUC4. The immunosensor was optimized with respect to several parameters and is very promising for clinical applications, having a limit of detection of 0.33μgmL−1 and a linear domain between 1 and 15μgmL−1 obtained by electrochemical impedance spectroscopy measurements.

Inhibition-based first-generation electrochemical biosensors: theoretical aspects and application to 2,4-dichlorophenoxy acetic acid detection.

In this work, several theoretical aspects involved in the first-generation inhibition-based electrochemical biosensor measurements have been discussed. In particular, we have developed a theoretical-methodological approach for the characterization of the kinetic interaction between alkaline phosphatase (AlP) and 2,4-dichlorophenoxy acetic acid (2,4-D) as representative inhibitor studied by means of cyclic voltammetry and amperometry. Based on these findings, a biosensor for the fast, simple, and inexpensive determination of 2,4-D has been developed. The enzyme has been immobilized on screen-printed electrodes (SPEs). To optimize the biosensor performances, several carbon-based SPEs, namely graphite (G), graphene (GP), and multiwalled carbon nanotubes (MWCNTs), have been evaluated. AlP was immobilized on the electrode surface by means of polyvinyl alcohol with styryl-pyridinium groups (PVA-SbQ) as cross-linking agent. In the presence of ascorbate 2-phosphate (A2P) as substrate, the herbicide has been determined, thanks to its inhibition activity towards the enzyme catalyzing the oxidation of A2P to ascorbic acid (AA). Under optimum experimental conditions, the best performance in terms of catalytic efficiency has been demonstrated by MWCNTs SPE-based biosensor. The inhibition biosensor shows a linearity range towards 2,4-D within 2.1-110 ppb, a LOD of 1 ppb, and acceptable repeatability and stability. This analysis method was applied to fortified lake water samples with recoveries above 90%. The low cost of this device and its good analytical performances suggest its application for the screening and monitoring of 2,4-D in real matrices.

Study of Different Carbonaceous Materials as Modifiers of Screen-Printed Electrodes for Detection of Catecholamines

This paper describes the sensing properties of carbon-based screen-printed electrodes modified with three types of carbonaceous materials: 1) carbon nanotubes; 2) carbon microfibers; and 3) graphene. The electrochemical signals of screen-printed electrodes toward catechol derivatives were registered. It was demonstrated that the screen-printed electrodes modified with carbon nanofibers show the best performances in terms of kinetics, stability, and the smallest detection limit for all the catechol derivatives analyzed. Experimental conditions on the sensing performance of the screen-printed electrodes were investigated and optimized. The sensors displayed linear responses to catecholamines over concentration ranges from 1 $\mu $ M to 60 $\mu $ M with detection limits in the range of 0.84–3.52 $\mu $ M. An array of electrodes was constructed using the signals of three types of electrodes. Principal component analysis of voltammetric data shows that the array was able to discriminate among catechol derivatives. The sensors were successfully applied to determine trace amounts of catecholamines in plasma.

Performances of carbon-based screen-printed electrodes modified by diazonium salts with various carboxylic functions for trace metal sensors

The electrochemically induced functionalization of carbon-based screen-printed-electrodes (SPEs) by phenyl groups, having one or two carboxylic functions, was achieved by reduction of in situ generated diazonium salts in aqueous media. The corresponding diazonium cations of 4-aminobenzoic acid, 4-aminophthalic acid, 3-(4-aminophenyl) propionic acid, 3-(4-aminophenyl)-2-propenoic acid and 5-aminoisophthalic acid were generated in situ with sodium nitrite in aqueous H2SO4. The electrochemical detection of Pb(II) with the grafted SPEs was investigated using Pb(II) 5×10−8M solutions. The performances of the grafted SPEs were found to be dependent on the number of carboxylic groups, on their position on the phenyl ring, on the olefinic or the aliphatic character of the chain bearing the carboxylic group. The performances of mono-4-carboxyphenyl and 3,5-dicarboxyphenyl grafted SPEs for Cd(II) and Cu(II) trace detection were tested and compared.

Screen-printed electrodes for electroanalytical sensing, of chromium VI in strong acid media

Simple, low-cost and acid-resistant carbon-based screen-printed electrodes (SPEs) addressed to detection of hexavalent chromium species, Cr(VI), in sulfuric acid at pH about 1, were prepared and characterized. Working and counter electrodes were prepared jointly on the same substrate in a single strip (working-counter electrodes pair). The batch printing process allowed obtaining many working-counter electrode pairs in a unique step. The developed working electrodes are comprised of several layers deposited on an alumina substrate: (1) bottom silver conductor, (2) dense organic–graphite composite conductor, (3) active layer consisting of a porous organic–graphite composite which contains a Cr(III) ionophore for testing Cr(III) obtained after reducing Cr(VI), and (4) an insulating and protective dielectric. All materials except the bottom Ag conductor were made on an organic matrix based on a thermoplastic polymer, polyvinylbutyral (PVB). The amperometric determination of Cr(VI) species at pH 1 was performed over a wide concentration range (dynamic range 3μM–40mM). The range for linear amperometric response is 3μM–10mM, with sensitivity about 0.08mAmM−1. The sensitivity is improved in comparison with previously developed sensors, while keeping a low limit of detection (LOD about 1μM). The response of the sensors are not interfered by the presence of Cr(III) in the solution, although the sensor can detect local formation of Cr(III) at the electrode surface after the reduction of Cr(VI) when diethylenetriamine-pentaacetic acid (DTPA), a complexing agent for Cr(III) is incorporated into the pastes.

Electrochemically Assisted Injection in Combination with Capillary Electrophoresis‐Mass Spectrometry (EAI‐CE‐MS) – Mechanistic and Quantitative Studies of the Reduction of 4‐Nitrotoluene at Various Carbon‐Based Screen‐Printed Electrodes

AbstractElectrochemically assisted injection (EAI) is a recently introduced injection concept for capillary electrophoresis (CE) enabling the separation of neutral analytes by means of electrochemical generation of charged species during the injection process. EAI‐CE is particularly attractive in combination with mass spectrometry (MS) leading to enhanced performance of MS detection. In this work, a fully automated EAI injection device was developed and applied to mechanistic and quantitative studies of the reduction of 4‐nitrotoluene (4‐NT). Three different carbon‐based screen‐printed electrodes (SPEs) were used including unmodified carbon, carbon nanofiber and reduced graphene oxide SPEs. Under acidic conditions the main products of 4‐NT reduction were 4‐hydroxylaminotoluene (4‐HAT) and 4‐aminotoluene (4‐AT). The EAI‐CE‐MS approach enabled the separation and selective determination of both compounds. On the basis of this methodical concept it was possible to study the formation of reduction products of 4‐NT in dependence on electrode potential and electrode material. In contrast to conventional electrochemical techniques like cyclic voltammetry EAI‐CE‐MS provides detailed information regarding changes of the product composition in dependence on various experimental conditions. Over the complete potential range studied the ratio of 4‐HAT/4‐AT was clearly different for the reduced graphene oxide SPE compared to the unmodified carbon and carbon fiber SPE. The construction of mass voltammograms added considerably to the information content of voltammetric experiments. Another aspect of this work was the reliable quantitative determination of 4‐NT by EAI‐CE‐MS using isotopically labeled 4‐NT as an internal standard. In this way the “classical” problem of changing response characteristics at solid electrodes could be eliminated based on the assumption that the target analyte and its isotopically labeled form behave in the same way. A corresponding protocol for quantitative EAI‐CE‐MS determinations of 4‐NT was elaborated and applied to standard solutions and spiked soil samples.

Orages surrenaliens

Carbon-based screen-printed electrodes are suitable for uric acid detection. Xanthine oxidase (XO) was immobilized either directly on the surface of the electrode or in a reactor with CPG aminopropylsilane in a FIA assembly. Higher reproducibility and lifetime was obtained with the reactor. Optimum conditions were found for the determination of Hypoxanthine (Hx), Inosine (HxR) and Inosine monophosphate (IMP). Calibration curves for IMP, HxR and Hx are linear up to 50 μM with detection limit of 1 μM for 50 μl injection. One assay is completed within 30 s. The reproducibility of 20 μM of Hx was obtained with CV 2%.

Screen-printed Electrochemical Chromium (VI) Sensing Electrodes for Effluent Bioremediation Monitoring

In this work, we introduce a simple, low-cost and acid-resistant materials system for carbon-based screen-printed electrodes (SPEs), and apply it to chemical sensing of hexavalent chromium, i.e. Cr(VI), in acid environments, as encountered in bioremediation of industrial effluents. The developed composite materials comprised of 1) dense organic-carbon conductor, 2) porous polymer-carbon-ligand active sensing material, and 3) insulating and protective dielectric. All materials were formulated with two different organic matrices, polyvinylbutyral (PVB) or epoxy resin (EP). The selected ionophore for chromium detection was diethylenetriamine-pentaacetic acid (DTPA). Both variants allowed Cr(VI) sensing over a wide concentration range in acid media.

Microfluidic Immunosensor with Micromagnetic Beads Coupled to Carbon-Based Screen-Printed Electrodes (SPCEs) for Determination of Botrytis cinerea in Tissue of Fruits

A wide range of plant species, including economically important crops such as vegetables, ornamentals, bulbs, and fundamentally fruits, can be affected by gray mold caused by the fungal pathogen Botrytis cinerea . This paper describes the development of a microfluidic immunosensor with micromagnetic beads (MMBs) coupled to carbon-based screen-printed electrodes (SPCEs) for the rapid and sensitive quantification of B. cinerea in apple (Red Delicious), table grape (pink Moscatel), and pear (William's) tissues. The detection of B. cinerea was carried out using a competitive immunoassay method based on the use of purified B. cinerea antigens immobilized on 3-aminopropyl-modified MMBs. The total assay time was 40 min, and the calculated detection limit was 0.008 μg mL(-1). Moreover, the intra- and interassay coefficients of variation were below 7%. The developed method allowed detects B. cinerea even in asymptomatic fruits and promises to be particularly useful for application in the agricultural industry.

Determination of arylsulphatase and phosphatase enzyme activities in soil using screen-printed electrodes modified with multi-walled carbon nanotubes

Sustainability of agricultural systems has become an important issue all over the world. The activity of enzymes is potentially an important quality bioindicator in soils. The aim of the present study was to develop a simple and convenient assay to determine the activity of arylsulphatase (AS), acid (ACP) and alkaline phosphatase (ALP) in agricultural soil. The activities of these enzymes were detected using a non-electroactive substrate, which produces an electroactive product. To this end, p-aminophenyl phosphate (pAPP) was used as a substrate which is converted to p-aminophenol (pAP) after enzymatic dephosphorylation; and 4-nitrocatechol sulphate (4-NCS) was used as a substrate for AS activity based on its catalytic effect on the hydrolysis of 4-NCS into 4-nitrocatechol (4-NC). The products of both enzymatic reactions were quantified on carbon-based screen-printed electrodes (SPCEs) modified with carbon nanotubes (CNTs), using Osteryoung square-wave voltammetry (OSWV). The determination of the reaction products allowed more sensitive determination of ALP, ACP and AS activities in soil than that obtained with a spectrophotometric method. This assay also diminishes the generation of waste, which is desirable in green analytical chemistry. The optimization of the analytical procedure in terms of the nature of electrode type, applied potential, pH of solution, and precision of measurements is reported.

Screen-printed immunosensor modified with carbon nanotubes in a continuous-flow system for the Botrytis cinerea determination in apple tissues

Botrytis cinerea is a plant-pathogenic fungus that produces the disease known as grey mould in a wide variety of agriculturally important hosts in many countries. This paper describes the development of an immunosensor coupled to carbon-based screen-printed electrodes (SPCE) modified with multi-walled carbon nanotubes (CNTs), which show a rapid and sensitive determination of B. cinerea in apple tissues (Red-delicious) using a competitive immunoassay method.Both the infected plant tissue sample and the B. cinerea-specific monoclonal antibody are allowed to react immunologically with the B. cinerea purified antigens immobilized on a rotating disk. Then, the bound antibodies are quantified by a horseradish peroxidise (HRP) enzyme labeled second antibodies specific to mouse IgG, using 4-tertbutylcatechol (4-TBC) as enzymatic mediators. The HRP, in the presence of hydrogen peroxide, catalyses the oxidation of 4-TBC to 4-tertbutyl o-benzoquinone. The electrochemical reduction back to 4-TBC is detected on SPCE-CNT at −0.15V. The response current is inversely proportional to the amount of the B. cinerea antigens present in the fruit sample. The time consumed per assay was 30min and the calculated detection limits for electrochemical method and the ELISA procedure are 0.02 and 10μgmL−1, respectively. Moreover the intra- and inter-assay coefficients of variation were below 7%. This electrochemical immunosensor promises to be usefully suited to the detection and quantification of B. cinerea in apparently healthy plant prior to the development of the symptoms.

Improvement of analytical performances of a disposable electrochemical immunosensor by using magnetic beads

A comparison of two electrochemical immunosensing strategies for PCBs detection, based on the use of two different solid phases, is here discussed. In both cases, carbon-based screen-printed electrodes (SPEs) are used as transducers in a direct competitive immunoassay scheme, where PCBs in solution compete with the tracer PCB28-alkaline phosphatase (AP) labeled for antibodies immobilized onto the solid-phase. In the standard format (called EI strategy), SPEs are both the solid-phase for immunoassay and electrochemical transducers: in this case the immunochemical reaction occurs onto the working electrode. Finally, the enzymatic substrate is added and an electroactive product is generated and detected by electrochemical measurement. In order to improve the performances of the system, a new approach (called EMI strategy) is developed by using functionalized magnetic beads as solid phase for the competitive assay; only after the immunosensing step they are captured by a magnet onto the working surface of the SPE for the electrochemical detection. Experimental results evidenced that the configuration based on the use of separate surfaces for immunoassay and for electrochemical detection gave the best results in terms of sensitivity and speed of the analysis. The improvement of analytical performances of the immunosensor based on EMI strategy was also demonstrated by the analysis of some spiked samples.

One-shot screen-printed thylakoid membrane-based biosensor for the detection of photosynthetic inhibitors in discrete samples

Screen-printing technology offers the possibility to produce a large number of sensors at low cost. Thus, due to their intrinsic characteristics and reproducibility, screen-printed electrodes can be used in the development of disposable electrochemical devices. In the present work, carbon-based screen-printed electrodes (SPCEs) have been used to develop a one-shot-measure biosensor for the detection of photosynthetic inhibitors in discrete samples. The measurement was based on the electrochemical evaluation of the activity of photosystem II (PSII), a protein complex present in photosynthetic organisms and involved in the photosynthesis. The biosensor was prepared by the modification of the working electrode of a SPCE, using thylakoid membranes extracted from spinach leaves. The modified sensors were then used as one-shot system to measure the presence of PSII activity inhibitors in discrete standard solutions. The coupling of the developed biosensor with a custom-made cell made it possible to perform tests using only 50 μL of total sample volume with a measurement time of 10 min. Inhibition curves were recorded for some photosynthetic inhibitors in a concentration range of 10 −6 to 10 −8 mol L −1. A reproducibility (relative standard deviation, R.S.D.%) of 10% was found and the calculated limit of detections (LODs) were in the nanomolar range. The effect of storage on sensitivity and reproducibility of a biosensor prepared by direct lyophilisation of thylakoid membranes on the electrode surface was also evaluated, confirming the possible use of the modified sensor up to one week after the preparation. Measurements on real samples were also reported, comparing the results with those obtained using a fluorescence-based commercial instrument for the analysis of photosynthetic inhibitors.

Biocompatible carbon-based screen-printed electrodes for the electrochemical detection of nitric oxide

We report in this study on the first use of carbon-based screen-printed electrodes (SPCEs) for the development of inexpensive, disposable and biocompatible electrochemical sensors for NO in solution. First, the screen printing electrode process was performed on two types of substrates and the chemical modification of the obtained electrodes was achieved in order to endow them with the desired sensitivity, selectivity and biocompatibility. The first important step in building the sensor system consisted into transposing existing chemical modifications to design selective and sensitive coatings towards NO. The second major and novel step of this work was devoted to confer to the electrode material the desired biocompatibility character by overcoating the whole chemically modified SPCEs with an additional layer of poly-oxyethyleneglycol (PEG) polymers. Since the biocompatible property of materials is generally linked to their hydrophilic character, the biocompatibility of the designed electrodes was assessed by sessile drop contact angle measurements. Finally, the performances of the electrodes towards NO were evaluated by chronoamperometric measurements.

Magnetic Bead-Based Chemiluminescent Metal Immunoassay with a Colloidal Gold Label

A novel, sensitive chemiluminescent (CL) immunoassay has been developed by taking advantage of a magnetic separation/mixing process and the amplification feature of colloidal gold label. First, the sandwich-type complex is formed in this protocol by the primary antibody immobilized on the surface of magnetic beads, the antigen in the sample, and the second antibody labeled with colloidal gold. Second, a large number of Au3+ ions from each gold particle anchored on the surface of magnetic beads are released after oxidative gold metal dissolution and then quantitatively determined by a simple and sensitive Au3+-catalyzed luminol CL reaction. Third, this protocol is evaluated for a noncompetitive immunoassay of a human immunoglobulin G, and a concentration as low as 3.1 x 10(-12) M is determined, which is competitive with colloidal gold-based anodic stripping voltammetry (ASV), colorimetric ELISA, or immunoassays based on fluorescent europium chelate labels. The high performance of this protocol is related to the sensitive CL determination of Au3+ ion (detection limit of 2 x 10(-10) M), which is 25 times higher than that by ASV at a single-use carbon-based screen-printed electrode. From the analytical chemistry point of view, this protocol will be quite promising for numerous applications in immunoassay and DNA hybridization.