A Simple Method to Tune Up Screen‐Printed Carbon Electrodes Applicable to the Design of Disposable Electrochemical Sensors

We report an easy method to tune up screen‐printed carbon electrodes (SPCEs) for application in fabricating disposable electrochemical sensors. Simply by ultrasonic polishing a bare SPCE in a γ‐Al₂O₃ slurry, the surface roughness was drastically smoothed coupled with a large increase in hydrophilicity. The as‐generated micromorphology on the surface of the SPCE was found to be ideal for the immobilization of catechol to minimize the overpotential in the sensitive detection of nicotinamide adenine dinucleotide (NADH) and hydrazine. Physical characterization by both XPS and AFM studies specify that the adsorption behavior is related to the carbon surface functionalities and the trapping of γ‐Al₂O₃ on the polished‐SPCE.     

Improving the detection of hydrogen peroxide of screen-printed carbon paste electrodes by modifying with nonionic surfactants

Nonionic surfactants, such as Triton X-100 and Tween-20, were shown in this study to improve the electrocatalytic activity of screen-printed carbon paste electrodes (SPCE). The electrochemical response of SPCE to hydrogen peroxide increased 8-10-fold with the modification of nonionic surfactants. In addition, the glucose biosensors fabricated from nonionic surfactant-modified SPCE exhibited 6.4-8.6-fold higher response to glucose than that fabricated from unmodified SPCE. A concentration effect is proposed for nonionic surfactant to bring neutral reactants to the surface of electrode. Moreover, nonionic surfactant-modified SPCE exhibits a capability of repetitive usage and good reproducibility (R.S.D. < 5%) in the measurement of H₂O₂. Interestingly, the nonionic surfactant-modified SPCE exhibited an opposite effect to ascorbic acid, a common electroactive agent, which causes interference during clinical diagnosis. The differential responses of nonionic surfactant-modified SPCE to H₂O₂ and ascorbic acid suggest its potential in the development of biosensors for clinical diagnosis.     

Electroanalytical Sensor Based on Unmodified Screen‐Printed Carbon Electrode for the Determination of Levo‐Thyroxine

The electrochemical behaviour of thyroxine (T₄) is analysed using the disposable screen‐printed carbon electrode (SPCE) in the neutral phosphate buffer solution with cyclic voltammetric technique. The Differential Pulse Voltammetry and Chronoamperometry were employed for sensing of T₄. The lowest detection limit of 3 nM was obtained from the differential pulse voltammetric method without preconditioning. The Density Functional Theoretical study of T₄ was performed to elucidate the mechanism of oxidation. The analysis of the commercial pharmaceutical samples indicates the validity of the proposed method.     

Heavy metal-free electrochemical detection of pyrophosphate ions by Nafion/carbon dots decorated screen printed carbon electrodes

We employ Nafion-mixed carbon dots (CDs) and low-cost screen-printed carbon electrodes (SPCEs) as foundation matrices for the fabrication of electrochemical biosensors. The  NH₂ and  COOH functional groups present on the SPCE surface after Nafion/CDs deposition allow for pyrophosphate ions (PPis) collection. Using Fe(CN)₆³⁻ as the electrochemical mediator, the SPCE-Nafion/CDs are applied to the detection of aqueous PPi by square wave voltammetry. Between 50 and 1 μM, a linear connection is established between the square wave voltammetry current and the PPi concentration. The limit of detection is determined to be 1.01 μM, and recoveries of 113% (±1.9%) and 108% (±3.9%) are achieved for human urine samples spiked with 6 and 3 μM of PPi, respectively. Furthermore, this PPi assay is suitable for the usage of complicated urine matrices without the inclusion of heavy metals. We anticipate that this unique approach will be beneficial for PPi level monitoring in urine during therapeutic treatments of illnesses and malignancies.     

Sensitive Electrochemical Quantification of Proanthocyanidins in Grapevine (Vitis vinifera) by Utilizing Disposable Screen-printed Carbon Electrodes

This work presents quantification of proanthocyanidins (PAs) isolated from grapevine using disposable screen-printed carbon electrodes (SPCE). Procyanidin B2 (B2) used as a model to investigate the electrochemical characteristics of complicated PAs structures in Britton Robinson buffer solution using cyclic voltammetry and square wave voltammetry. B2 exhibits a well-defined reversible redox wave at +0.49 V vs. Ag/AgCl. Significantly, the B2 was determined over a linear concentration range of 3.45–34.6 μM with a detection limit of 2.07 μM. The SPCE was used to analyze PAs in grapevine samples, and the results were consistent with those obtained using Folin-Ciocalteu standard method.     

Electrochemical Determination of Pyrogallol at Conducting Poly(3,4‐ethylenedioxythiophene) Film‐Modified Screen‐Printed Carbon Electrodes

The electrochemical oxidation of pyrogallol at electrogenerated poly(3,4‐ethylenedioxythiophene) (PEDOT) film‐modified screen‐printed carbon electrodes (SPCE) was investigated. The voltammetric peak for the oxidation of pyrogallol in a pH 7 buffer solution at the modified electrode occurred at 0.13 V, much lower than the bare SPCE and preanodized SPCE. The experimental parameters, including electropolymerization conditions, solution pH values and applied potentials were optimized to improve the voltammetric responses. A linear calibration plot, based on flow‐injection amperometry, was obtained for 1–1000 µM pyrogallol, and a slope of 0.030 µA/µM was obtained. The detection limit (S/N=3) was 0.63 µM.     

A novel poly(3,4-ethylenedioxythiophene)/iron phthalocyanine/multi-wall carbon nanotubes nanocomposite with high electrocatalytic activity for nitrite oxidation

In the present work, the oxidative electrochemistry of nitrite on the poly(3,4-ethylenedioxythiophene)/iron phthalocyanine/multi-wall carbon nanotubes-(PEDOT/FePc/MWCNT) modified screen-printed carbon electrodes (SPCE) has been investigated. The parameters, such as overpotential, current density and rate constant at PEDOT/FePc/MWCNT-modified SPCE, were compared with an un-modified, FePc-, and FePc/MWCNT-modified SPCE for electro-oxidation of nitrite. As compared with the un-modified SPCE, an increase in the anodic peak current density (J_pa) (∼100%) along with a decrease in the anodic peak potential (E_pa) of ∼150 mV for electro-oxidation of nitrite at the FePc-modified SPCE was observed. When an under-layer of MWCNT was introduced onto FePc-modified SPCE, denoted as FePc/MWCNT-modified SPCE, and the number of FePc/MWCNT bilayer was optimized, the heterogeneous electron transfer rate constant (k) at FePc/MWCNT-modified SPCE was enhanced about 7.8 times as compared with that at FePc-modified SPCE. Moreover, as a layer of PEDOT film was electrodeposited onto the FePc/MWCNT-modified SPCE, denoted as PEDOT/FePc/MWCNT-modified SPCE, a significant increase in current response along with a remarkable decrease in E_pa were noticed. This can be attributed to the pre-concentration effect induced by the electrostatic interaction between the negatively charged nitrite and oxidized PEDOT film. On the whole, the PEDOT/FePc/MWCNT-modified SPCE greatly reduces the overpotential of ∼330 mV along with 3.5 times enhanced the peak current density for the electro-oxidation of nitrite as compared with un-modified SPCE. The sensitivity and limit of detection (S/N = 3) for the PEDOT/FePc/MWCNT-modified SPCE were found to be as 638 mA cm⁻² M⁻¹ and 71 nM, respectively. Notably, PEDOT/FePc/MWCNT-modified SPCE has a lower sensing potential than compared to several other modified electrodes. The developed sensor was also applied for the determination of nitrite in tap water sample.     

Surface Polymers on Multiwalled Carbon Nanotubes for Selective Extraction and Electrochemical Determination of Rhodamine B in Food Samples

In this study, we combine magnetic solid phase extraction (MSPE), with the screen-printed carbon electrode (SPCE) modified by a molecular imprinted polymer (MIP) for sensitive and selective extraction and electrochemical determination of Rhodamine B in food samples. A magnetic solid phase extraction (MSPE) was carried out using magnetic poly(styrene-co-divinylbenzene) (PS-DVB) and magnetic nanoparticles (MNPs) synthetized on the surface of multiwalled carbon nanotubes (MWCNTs). An MIP was prepared on the surface of MWCNTs in the presence of titanium oxide nanoparticles (TiO₂NPs) modifying the SPCE for the rapid electrochemical detection of Rhodamine B. The MIPs synthesis was optimized by varying the activated titanium oxide (TiO₂) and multiwalled carbon nanotubes (MWCNTs) amounts. The MSPE and electrochemical detection conditions were optimized as well. The present method exhibited good selectivity, high sensitivity, and good reproducibility towards the determination of Rhodamine B, making it a suitable method for the determination of Rhodamine B in food samples.     

Electrochemical study and flow injection analysis of paracetamol in pharmaceutical formulations based on screen-printed electrodes and carbon nanotubes

Acetaminophenol or paracetamol is one of the most commonly used analgesics in pharmaceutical formulations. Acetaminophen is electroactive and voltammetric mechanistic studies for the electrode processes of the acetaminophenol/N-acetyl-p-quinoneimine redox system are presented. Carbon nanotubes modified screen-printed electrodes with enhanced electron transfer properties are used for the study of the electrochemical-chemical oxidation mechanism of paracetamol at pH 2.0.Quantitative analysis of paracetamol by using its oxidation process (in a Britton-Robinson buffer solution pH 10.0) at +0.20 V (vs. an Ag pseudoreference electrode) on an untreated screen-printed carbon electrode (SPCE) was carried out. Thus, a cyclic voltammetric based reproducible determination of acetaminophen (R.S.D., 2.2%) in the range 2.5 × 10⁻⁶ M to 1 × 10⁻³ M, was obtained. However, when SPCEs are used as amperometric detectors coupled to a flow injection analysis (FIA) system, the detection limit achieved for paracetamol was 1 × 10⁻⁷ M, one order of magnitude lower than that obtained by voltammetric analysis. The repeatability of the amperometric detection with the same SPCE is 2% for 15 successive injections of 10⁻⁵ M acetaminophen and do not present any memory effect.Finally, the applicability of using screen-printed carbon electrodes for the electrochemical detection of paracetamol (i.e. for quality control analysis) was demonstrated by using two commercial pharmaceutical products.     

CuAg nanoparticles formed in situ on electrochemically pre‐anodized screen‐printed carbon electrodes for the detection of nitrate and nitrite anions

CuAg nanoparticles (CuAgNPs) were electrochemically formed in situ on pre‐anodized, screen‐printed carbon electrodes (SPCEs) that possessed many oxygen‐containing functional groups capable of adsorbing metal ions, namely Cu²⁺ and Ag⁺. Pre‐anodization was achieved using continuous cyclic voltammetry in the range of potential 0.3–2.0 V under a scan rate of 50 mV/s. Cu²⁺ and Ag⁺ ions were adsorbed on the pre‐anodized SPCE by immersing the electrode in solutions containing both metal ions, and then CuAgNPs were formed in situ via electrochemical reduction in a deaerated, neat NaClO₄ solution after the electrode was ultrasonicated to remove physically adsorbed metal ions. Although CuNPs showed higher activity than AgNPs toward both nitrate (NO₃⁻) and nitrite (NO₂⁻) ions, the instability of CuNPs hindered the application, so CuAgNPs were employed to achieve a compromise between sensitivity and stability. The SPCE/anodized/CuAgNP electrodes showed activity toward the electrochemical reduction of NO₃⁻ and NO₂⁻, respectively, with the limit of detection (LOD) of 15.6 μM (0.97 ppm) and 11.1 μM (0.51 ppm), which is sufficient to fit the allowed values (50 and 3 ppm, respectively) in drinking water as suggested by the World Health Organization (WHO).     

Amperometric Magnetoimmunosensors for Direct Determination of D‐Dimer in Human Serum

Two different D‐dimer disposable amperometric immunosensing designs based on indirect competitive or sandwich formats and the use of carboxylic acid‐modified magnetic beads (COOH‐MBs) and screen‐printed carbon electrodes (SPCEs) have been developed and compared. In both approaches, the resulting modified MBs were magnetically captured on the surface of a SPCE which was used as the transducer for the electrochemical detection at ?0.20 V upon addition of H₂O₂, and hydroquinone (HQ). Both configurations exhibited linear ranges of clinical usefulness and detection limits quite below the clinical threshold (0.5 µg mL^?1 D‐dimer). The sandwich configuration has been successfully tested with serum samples.     

Electroanalytical Application of Carbon Based Electrodes to the Pharmaceuticals

Abstract

Carbon and its derivatives, as the high performance material, occupy a special place in electrochemistry due to its ‐in many ways‐ extreme properties. Recent trends and advances in the electrochemistry of carbon‐based electrodes are reviewed. The varieties of carbon‐based electrodes, their basic physicochemical properties and some characteristics are surveyed. Special attention is paid to the possibilities of carbon‐based electrodes in electroanalytical investigation in pharmaceutical dosage forms and biological samples using modern electrochemical techniques. This review includes a summary of the rules that must be considered for drug analysis from its dosage forms and biological samples using carbon‐based electrodes. The present review is the first comprehensive report on the heterogeneous and homogeneous carbon electrodes, and an addition to many excellent reviews on carbon electrodes in the literature. This review summarizes some of the recent developments and applications of carbon‐based electrodes for drug compounds in their dosage forms and in biological samples in the period from 1996 till 2006. Also some further selected designs (screen‐printed; carbon nanotubes, etc.) and applications have been discussed.     

Detection of Allergenic Lysozyme during Winemaking with an Electrochemical Aptasensor

In this work we investigate the performance of a simple, disposable electrochemical aptasensor for lysozyme and its usefulness for monitoring the allergen risk along wine production. The sensor relies on screen‐printed gold electrodes modified with gold nanoparticles as the electrochemical transducer, with detection by cyclic voltammetry. This simple method is characterized by a detection limit of 0.32 μg.mL^?1 lysozyme and a linear range of 1–10 μg.mL^?1, being appropriate for the analysis of lysozyme‐treated wines. Several white wines where sulphur dioxide was partially replaced by lysozyme were produced and analyzed with the aptasensor at critical stages during wine production. The results obtained with the aptasensor were moreover compared with those recorded in parallel by a standard method, high performance liquid chromatography (HPLC). The specific advantages brought by the use of nanomaterial and the limitations of the sensor are discussed. The sensor allowed evaluating the effect of various technological steps along wine production on the content of lysozyme.     

Disposable Amperometric Biosensor Based on Poly‐L‐lysine and Fe3O4 NPs‐chitosan Composite for the Detection of Tyramine in Cheese

An amperometric tyramine biosensor based on poly‐L‐lysine (PLL) and Fe₃O₄ nanoparticles (Fe₃O₄NP) modified screen printed carbon electrode (SPCE) was developed. PLL was formed on the SPCE by the electropolymerization of L‐lysine. Subsequently, Fe₃O₄NP suspension prepared in chitosan (CH) solution was casted onto the PLL/SPCE. Tyrosinase (Ty) enzyme was immobilized onto the modified Fe₃O₄?CH/PLL/SPCE and the electrode was coated with Nafion to fabricate the Ty/Fe₃O₄?CH/PLL/SPCE. Different techniques including scanning electron microscopy, chronoamperometry (i–t curve), cyclic voltammetry and electrochemical impedance spectroscopy were utilized to study the fabrication processes, electrochemical characteristics and performance parameters of the biosensor. The analytical performance of the tyramine biosensor was evaluated with respect to linear range, sensitivity, limit of detection, repeatability and reproducibility. The response of the biosensor to tyramine was linear between 4.9×10^?7–6.3×10^?5 M with a detection limit of 7.5×10^?8 M and sensitivity of 71.36 μA mM^?1 (595 μA mM^?1 cm^?2). The application of the developed biosensor for the determination of tyramine was successfully tested in cheese sample and mean analytical recovery of added tyramine in cheese extract was calculated as 101.2±2.1 %. The presented tyramine biosensor is a promising approach for tyramine analysis in real samples due to its high sensitivity, rapid response and easy fabrication.     

Glassy carbon and boron doped glassy carbon electrodes for voltammetric determination of linuron herbicide in the selected samples

In this study the application of home-made unmodified (GC) and bulk modified boron doped glassy carbon (GCB) electrodes for the voltammetric determination of the linuron was investigated. The electrodes were synthesized with a moderate temperature treatment (1000°C). Obtained results were compared with the electrochemical determination of the linuron using a commercial glassy carbon electrode (GC-Metrohm). The peak potential (E _p ) of linuron oxidation in 0.1 mol dm⁻³ H₂SO₄ as electrolyte was similar for all applied electrodes: 1.31, 1.34 and 1.28 V for GCB, GC and GC-Metrohm electrodes, respectively. Potential of linuron oxidation and current density depend on the pH of supporting electrolyte. Applying GCB and GC-Metrohm electrodes the most intensive electrochemical response for linuron was obtained in strongly acidic solution (0.1 mol dm⁻³ H₂SO₄). Applying the boron doped glassy carbon electrode the broadest linear range (0.005–0.1 μmol cm⁻³) for the linuron determination was obtained. The results of voltammetric determination of the linuron in spiked water samples showed good correlation between added and found amounts of linuron and also are in good agreement with the results obtained by HPLC-UV method. This appears to be the first application of a boron doped glassy carbon electrode for voltammetric determination of the environmental important compounds.      

Effect of pre-treatment on the surface and electrochemical properties of screen-printed carbon paste electrodes

The effect of various electrochemical pre-treatment methods on the surface and electrochemical properties of screen-printed carbon paste electrodes (SPCE) prepared with three different commercial products was examined. It was observed that a positively charged redox couple, e.g., hexaammineruthenium(III), exhibited quasi-reversible behavior at the untreated SPCE. However, the cyclic voltammograms (CVs) of the SPCE prepared with general-purpose carbon inks did not exhibit clear redox peaks to other representative redox couples [e.g., hexacyanoferrate(III), hexachloroiridate(IV), dopamine, and hydroquinone] without activation. Electrochemical pre-treatment methods were sought in four different aqueous solutions, i.e., sulfuric acid, potassium chloride, sodium hydrogencarbonate, and sodium carbonate, applying various activation potentials. It was found that the pre-treatment procedure in saturated Na2CO3 solution at 1.2 V provides a mild and effective condition for activating the SPCE. By measuring the water contact angles at the SPCE surfaces and recording their SEM images, it was confirmed that the electrochemical pre-treatment effectively removes the organic binders from the surface carbon particles. A prolonged period of activation (> 5 min) or the use of high potentials (> 1.2 V) increased the capacitance of the electrode over 20 microF cm(-2). The pre-treated SPCE behaved like a random array microelectrode, exhibiting a sigmoidal-shaped CV at a slow scan rate. The short pre-anodization method in Na2CO3 solution was generally applicable to most SPCE prepared with general-purpose carbon inks.     

Electrochemical determination of nitrite based on poly(amidoamine) dendrimer-modified carbon nanotubes for nitrite oxidation

This study describes a simple and reliable method for the electrochemical determination of nitrite based on poly(amidoamine)-modified carbon nanotubes. Amine-terminated poly(amidoamine) (generation 4.0, G4-NH₄) were covalently attached onto multi-walled carbon nanotube (MWNT)-modified glass carbon (GC) electrodes (written as G4-NH₄/MWNT-modified GC) and which were used for the electrochemical determination of nitrite. The studies show that the G4-NH₄/MWNT-modified electrodes demonstrated significantly enhanced electrochemical activity towards nitrite oxidation. Chronoamperometry studies reveal that the amperometric response is rapid, stable, and offers a linear dependence over a wide range of nitrite concentrations from 5 μM to 1.5 mM. The proposed method can be used for the continuous monitoring of nitrite in real samples. The electrochemical properties of the G4-NH₄/MWNT nanocomposites are reasonably envisaged to be promising for providing a nanostructured platform in the development of electrochemical sensors or biosensors.     

Book reviews

Inorganic mercury ions (Hg²⁺) in laboratory prepared solutions were determined with a screen-printed carbon electrode (SPCE) coated with a polyaniline-methylene blue (PANI-MB) polymer layer. The structure and properties of the PANI-MB polymer layer were compared to that of normal polyaniline (PANI) in order to elucidate the structure of the PANI-MB layer. The electrically-conducting polymers were prepared by electrochemical polymerisation of monomer solutions of aniline, and mixed solutions of aniline with methylene blue onto respective screen-printed carbon electrodes (SPCEs). Scanning Electron Microscopy (SEM) analyses of the SPCE polymer coated electrodes have shown that nanostructured materials have formed with the diameters of the PANI nanoclusters and PANI-MB nanorods at approximately 200 nm. Anodic stripping voltammetry (ASV) was used to evaluate a solution composed of 1 × 10^?6 M Hg²⁺, in the presence of the SPCE/PANI-MB polymer sensor electrode. The Hg²⁺ ions were determined as follows: (i) pre-concentration and reduction on the modified electrode surface and (ii) subsequent stripping from the electrode surface during the positive potential sweep. The experimental conditions optimised for Hg²⁺ determination included the supporting electrolyte concentration and the accumulation time. The results obtained have shown that the SPCE/PANI-MB polymer sensor electrode operates optimally at a pH 2, with the supporting electrolyte concentration at 0.5 M HCl. A linear calibration curve was found to be in the range of 1 × 10^?8 M to 1 × 10^?5 M Hg²⁺ after 120 s of pre-concentration. The detection limit was calculated and found to be 54.27 ± 3.28 µg L^?1 of Hg²⁺. The results have also shown that a conducting polymer modified SPCE sensor electrode can be used as an alternative transducer for the voltammetric stripping and analysis of inorganic Hg²⁺ ions.     

Direct Determination of Paracetamol in Environmental Samples Using Screen‐printed Carbon/Carbon Nanofibers Sensor – Experimental and Theoretical Studies

The paper describes the first electrochemical method (differential pulse adsorptive stripping voltammetry, DPAdSV) using a screen‐printed sensor with a carbon/carbon nanofibers working electrode (SPCE/CNFs) for the direct determination of low (real) concentrations of paracetamol (PA) in environmental water samples. By applying this sensor together with DPAdSV, two linear PA concentration ranges from 2.0×10^?9 to 5.0×10^?8 mol L^?1 (r=0.9991) and 1.0×10^?7–2.0×10^?6 mol L^?1 ( r=0.9994) were obtained. For the accumulation time of 90 s, the limit of detection was 5.4×10^?10 mol L^?1. Moreover, the SPCE/CNFs sensor and the DPADSV procedure for PA determination are potentially applicable in field analysis. The process of PA adsorption at the SPCE/CNFs surface was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and theoretical studies. In the theoretical study of the interaction of CNF and PA, the first species was modelled by graphene‐like clusters containing up to 37 rings. It was found that the preferable orientation of PA is parallel to the carbon surface with the binding energy of about ?68 kJ/mol calculated by symmetry‐adapted perturbation theory (SAPT). Both the selectivity and the accuracy of the developed sensor for real sample analysis were also investigated using Polish river and sea samples.     

Electrochemical Oxidation and Sensitive Determination of Pyrogallol at Preanodized Screen‐Printed Carbon Electrodes

In this study, we report a simple, low‐cost and rapid electrochemical sensor based on the anodically pretreated screen‐printed carbon electrodes (SPCE*) for the determination of pyrogallol in pH 7.0 buffer solutions. Cyclic voltammetric studies show that SPCE* lowers overpotentials and improve electrochemical behaviour of pyrogallol, compared to untreated SPCE. All experimental parameters were optimized to improve voltammetric responses; excellent analytical features were achieved by flow‐injection amperometric methods. A linear calibration plot was obtained for 10‐1000 μM pyrogallol with a slope of 0.0562 μA/μM. The detection limit (S/N = 3) was 0.33 μM. Interferences from some inorganic salts and organic compounds were studied. The assay was applied to the determination of pyrogallol in tap water and lake water, respectively.