Graphite Screen-printed Electrodes Research Articles

Electrochemical Nanosensor for the Simultaneous Determination of Anticancer Drugs Epirubicin and Topotecan Using UiO-66-NH2/GO Nanocomposite Modified Electrode.

In this work, UiO-66-NH2/GO nanocomposite was prepared using a simple solvothermal technique, and its structure and morphology were characterized using field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). An enhanced electrochemical sensor for the detection of epirubicin (EP) was proposed, which utilized a UiO-66-NH2/GO nanocomposite-modified screen-printed graphite electrode (UiO-66-NH2/GO/SPGE). The prepared UiO-66-NH2/GO nanocomposite improved the electrochemical performance of the SPGE towards the redox reaction of EP. Under optimized experimental conditions, this sensor demonstrates a remarkable limit of detection (LOD) of 0.003 µM and a linear dynamic range from 0.008 to 200.0 µM, providing a highly capable platform for sensing EP. Furthermore, the simultaneous electro-catalytic oxidation of EP and topotecan (TP) was investigated at the UiO-66-NH2/GO/SPGE surface utilizing differential pulse voltammetry (DPV). DPV measurements revealed the presence of two distinct oxidation peaks of EP and TP, with a peak potential separation of 200 mV. Finally, the UiO-66-NH2/GO/SPGE sensor was successfully utilized for the quantitative analysis of EP and TP in pharmaceutical injection, yielding highly satisfactory results.

Spectroscopic investigations of a commercial graphite screen printed electrode modified by bismuth oxide drop deposition and electrochemical reduction, for cadmium and lead ions simultaneous determination

A single use graphite screen-printed electrode (GSPE) was easily modified, to take advantage of the proven affinity of the nontoxic post-transition metal bismuth (Bi), for metal ions to be detected by Square Wave Anodic Stripping Voltammetry (SWASV). A bismuth oxide (Bi2O3) or a chitosan coated (CS@Bi2O3) nanopowder suspension was drop-casted on the graphite working electrode (WE) surface, giving rise to the precursor of a Bi-modified GSPE. After that, an electrochemical reduction was performed to obtain the Bi– or the CS@Bi–GSPE.X-ray photoelectron spectroscopy and micro-X-ray fluorescence investigations were performed on the graphitic structure pre and post modification. The bismuth oxide deposition amount was considered as critical parameter to sensor performance, indicating a minimum and maximum threshold. Under improved measurement conditions, with a 300 s pre-concentration time, the attained sensors exhibited a linearity in the range (2.0–20.0) μg L−1 in the simultaneous analysis of Pb(II) and Cd(II). The Bi–GSPE showed LODs of 1.7 and 0.5 μg L−1 for Cd(II) and Pb(II) respectively, while 1.5 μg L−1 for Cd(II) and 0.2 μg L−1 for Pb(II) were recorded by the CS@Bi–GSPE. As an applicative proof in real sample, a spike test was carried out in a ground water sample, without any preliminary sample treatment.

Pharmacogenomic Studies of Antiviral Drug Favipiravir.

In this work, we conducted a study of the interaction between DNA and favipiravir (FAV). This chemotherapeutic compound is an antiviral drug for the treatment of COVID-19 and other infections caused by RNA viruses. This paper examines the electroanalytical characteristics of FAV. The determined concentrations correspond to therapeutically significant ones in the range of 50-500 µM (R2 = 0.943). We have shown that FAV can be electro-oxidized around the potential of +0.96 V ÷ +0.98 V (vs. Ag/AgCl). A mechanism for electrochemical oxidation of FAV was proposed. The effect of the drug on DNA was recorded as changes in the intensity of electrochemical oxidation of heterocyclic nucleobases (guanine, adenine and thymine) using screen-printed graphite electrodes modified with single-walled carbon nanotubes and titanium oxide nanoparticles. In this work, the binding constants (Kb) of FAV/dsDNA complexes for guanine, adenine and thymine were calculated. The values of the DNA-mediated electrochemical decline coefficient were calculated as the ratio of the intensity of signals for the electrochemical oxidation of guanine, adenine and thymine in the presence of FAV to the intensity of signals for the electro-oxidation of these bases without drug (S, %). Based on the analysis of electrochemical parameters, values of binding constants and spectral data, intercalation was proposed as the principal mechanism of the antiviral drug FAV interaction with DNA. The interaction with calf thymus DNA also confirmed the intercalation mechanism. However, an additional mode of interaction, such as a damage effect together with electrostatic interactions, was revealed in a prolonged exposure of DNA to FAV.

Flow-Through Amperometric Biosensor System Based on Functionalized Aryl Derivative of Phenothiazine and PAMAM-Calix-Dendrimers for the Determination of Uric Acid.

A flow-through biosensor system for the determination of uric acid was developed on the platform of flow-through electrochemical cell manufactured by 3D printing from poly(lactic acid) and equipped with a modified screen-printed graphite electrode (SPE). Uricase was immobilized to the inner surface of a replaceable reactor chamber. Its working volume was reduced to 10 μL against a previously reported similar cell. SPE was modified independently of the enzyme reactor with carbon black, pillar[5]arene, poly(amidoamine) dendrimers based on the p-tert-butylthiacalix[4]arene (PAMAM-calix-dendrimers) platform and electropolymerized 3,7-bis(4-aminophenylamino) phenothiazin-5-ium chloride. Introduction of the PAMAM-calix-dendrimers into the electrode coating led to a fivefold increase in the redox currents of the electroactive polymer. It was found that higher generations of the PAMAM-calix-dendrimers led to a greater increase in the currents measured. Coatings consisted of products of the electropolymerization of the phenothiazine with implemented pillar[5]arene and PAMAM-calix-dendrimers showing high efficiency in the electrochemical reduction of hydrogen peroxide that was formed in the enzymatic oxidation of uric acid. The presence of PAMAM-calix-dendrimer G2 in the coating increased the redox signal related to the uric acid assay by more than 1.5 times. The biosensor system was successfully applied for the enzymatic determination of uric acid in chronoamperometric mode. The following optimal parameters for the chronoamperometric determination of uric acid in flow-through conditions were established: pH 8.0, flow rate 0.2 mL·min-1, 5 U of uricase per reactor. Under these conditions, the biosensor system made it possible to determine from 10 nM to 20 μM of uric acid with the limit of detection (LOD) of 4 nM. Glucose (up to 1 mM), dopamine (up to 0.5 mM), and ascorbic acid (up to 50 μM) did not affect the signal of the biosensor toward uric acid. The biosensor was tested on spiked artificial urine samples, and showed 101% recovery for tenfold diluted samples. The ease of assembly of the flow cell and the low cost of the replacement parts make for a promising future application of the biosensor system in routine clinical analyses.

Eco-friendly spark-generated CoxOy nanoparticle-modified graphite screen-printed sensing surfaces for the determination of H2O2 in energy drinks

The modification of graphite screen-printed electrodes (SPEs) is reported using an eco-friendly and extremely fast method based on the direct cobalt pin electrode-to-SPE spark discharge at ambient conditions. This approach does not utilize any liquids or chemical templates, does not produce any waste, and allows the in-situ generation of CoxOy nanoparticles onto the electrode surface and the development of efficient electrocatalytic sensing surfaces for the determination of H2O2. Co-spark SPEs were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy and x-ray photoelectron spectroscopy (XPS), revealing the formation of surface confined CoxOy nanoparticles and the diverse oxidation states of cobalt species. Co-spark SPEs were also characterized with cyclic voltammetry and electrochemical impedance spectroscopy. Redox transitions of the surface confined electrocatalysts are demonstrated by electrochemical polarization studies, showing the formation of different oxides (CoxOy), varying the XPS results. Amperometric measurements at 0.3 V vs. Ag/AgCl revealed a linear relationship between the current response and the concentration of H2O2 over the range 1 − 102 μM, achieving a limit of detection (3σ/m) of 0.6 μM. The interference effect of various electroactive species was effectively addressed by employing dual measurements in the absence and presence of the enzyme catalase. The analytical utility of the method was evaluated in antioxidant rich real-world samples, such as energy drinks, demonstrating sufficient recovery.Graphical

Simple and sensitive voltammetric sensor for in‐situ clinical and environmental 17‐β‐estradiol monitoring

AbstractThe direct electrochemical oxidation of 17‐β‐estradiol (E2) at conventional electrodes gives weak current signals making detection at trace levels difficult, as required for clinical and environmental applications. In order to strengthen the electrochemical behavior of E2, a simple and sensitive sensor has been realized based on a graphite screen printed electrode (GSPE) functionalized according to a two‐step procedure: i) drop‐casting deposition of gold nanoparticles (AuNPs); ii) electropolymerization of methylene blue (MB). The final PMB‐AuNPs‐GSPE platform was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The pH value was optimized in order to obtain the best detection efficiency and the highest peak current response was obtained at pH 7.0. The synergistic contributions of both AuNPs and PMB allowed the proposed sensor to show a wide linear range from 0.5 to 125.0 μmol L−1 with a LOD of 41 nmol L−1, long‐term stability and good reproducibility (RSD=2.9 % for n=10). Moreover, the sensor was able to distinguish E2 from several interfering compounds commonly present in urine and river water as well as from other endocrine‐ disrupting chemicals (EDCs), denoting its high specificity to E2 molecule. Finally, the developed electrode platform was successfully applied to the determination of E2 in both human urine and river water samples without any purification step under the standard addition method.

Synthesis of ZnO@TiO2 nanoparticles and its application to construct an electrochemical sensor for determination of hydrazine

In the present research, ZnO@TiO2 nanoparticles (ZnO@TiO2 NPs) was synthesized by using a simple method and the results of infrared (IR), X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and energy-dispersive X-ray spectroscopy (EDX) confirmed their synthesis. Then, an electrochemical sensor based on screen printed graphite electrode (SPGE) modified with ZnO@TiO2 NPs was developed for voltammetric detection of hydrazine in water samples. The ZnO@TiO2 NPs modified SPGE demonstrates significant performance toward the hydrazine detection due to the synergistic effect between ZnO NPs and TiO2 NPs and it proved by the results from cyclic voltammetry (CV). Also, the observation of an oxidation peak without a reduction peak in the opposite scan direction indicated the irreversibility of the electrochemical oxidation of hydrazine on both the bare SPGE and the ZnO@TiO2/SPGE. Under optimized conditions (pH and differential pulse parameters), the voltammetric current response of hydrazine at the ZnO@TiO2/SPGE showed linear dependence on the concentration, ranging from 0.01 µM to 585.0 µM with a limit of detection (LOD) of 0.005 µM. In addition, the pertinency of the ZnO@TiO2/SPGE sensor for practical applications was investigated by quantification detection of hydrazine in water samples. The findings showed recovery values between 97.3 % and 104.2 % and relative standard deviations (RSDs) ≤ 3.5 % for river and tap water samples.

Stereoselective Voltammetric Biosensor for Myo-Inositol and D-Chiro-Inositol Recognition.

This paper describes the development of a simple voltammetric biosensor for the stereoselective discrimination of myo-inositol (myo-Ins) and D-chiro-inositol (D-chiro-Ins) by means of bovine serum albumin (BSA) adsorption onto a multi-walled carbon nanotube (MWCNT) graphite screen-printed electrode (MWCNT-GSPE), previously functionalized by the electropolymerization of methylene blue (MB). After a morphological characterization, the enantioselective biosensor platform was electrochemically characterized after each modification step by differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The results show that the binding affinity between myo-Ins and BSA was higher than that between D-chiro-Ins and BSA, confirming the different interactions exhibited by the novel BSA/MB/MWCNT/GSPE platform towards the two diastereoisomers. The biosensor showed a linear response towards both stereoisomers in the range of 2-100 μM, with LODs of 0.5 and 1 μM for myo-Ins and D-chiro-Ins, respectively. Moreover, a stereoselectivity coefficient α of 1.6 was found, with association constants of 0.90 and 0.79, for the two stereoisomers, respectively. Lastly, the proposed biosensor allowed for the determination of the stereoisomeric composition of myo-/D-chiro-Ins mixtures in commercial pharmaceutical preparations, and thus, it is expected to be successfully applied in the chiral analysis of pharmaceuticals and illicit drugs of forensic interest.

IMMUNOSENSOR BASED ON SCREEN-PRINTED GRAPHITE ELECTRODES MODIFIED WITH GOLD NANOPARTICLES AND SYNTHETIC MEMBRANE-LIKE SUBSTANCE FOR THE DETERMINATION OF CHLORAMPHENICOL

An electrochemical immunosensor based on screen-printed graphite electrodes has been developed for the determination of the antibiotic chloramphenicol in water and milk samples. It has been shown that the immobilization of chloramphenicol-specific antibodies in a liquid crystal layer of a membrane-like didodecyldimethylammonium bromide preserves the mobility and accessibility of active centers of antibodies, and the addition of gold nanoparticles improves electron transfer from the electrode surface to the redox centers of horseradish peroxidase used as a label. The limit of detection of chloramphenicol in water was 0.02 μg/L, in milk - 0.04 μg/L. The method can be used to determine residual amounts of chloramphenicol in animal products.

Immunosensor Based on Screen-Printed Graphite Electrodes Modified with Gold Nanoparticles and a Synthetic Membrane-Like Substance for the Determination of Chloramphenicol

Immunosensor Based on Screen-Printed Graphite Electrodes Modified with Gold Nanoparticles and a Synthetic Membrane-Like Substance for the Determination of Chloramphenicol

A novel dsDNA decamer-based electrochemical biosensor for selective determination of irinotecan active metabolite - SN38

This paper presents a novel biosensor for detecting the active metabolite of irinotecan, SN38, with high selectivity and sensitivity. The biosensor utilizes a dsDNA decamer (5′-GCGTTGTCGC-3′) that selectively interacts with SN38. The biosensor, consisting of a screen-printed graphite electrode with the dsDNA decamer as the recognition layer, demonstrates stability, sensitivity, and selectivity towards SN38 through electrochemical studies. It offers a wide linear range of 1–200 nM, comparable to the high-performance liquid chromatography (HPLC) method, with a sensitivity of 57 nA/nM and a detection limit of 1.06 nM. Compared to a bare graphite electrode, the biosensor exhibits a significant 31-fold increase in sensitivity and a detection limit three orders of magnitude lower. Selectivity studies were conducted using electrochemically active and inactive interferents, including biologically active compounds. Bioreceptor interactions with chosen interferents were examined using HPLC and nuclear magnetic resonance (NMR). Tests of the biosensor was performed using laboratory samples and artificial urine samples spiked with SN38. This disposable biosensor, based on dsDNA, provides an innovative approach for accurately determining SN38 levels in the therapeutic drug concentration range. It holds promise as an alternative method for clinical diagnosis and monitoring of SN38 levels in cancer patients undergoing irinotecan treatment.

ZnO Hollow Quasi-Spheres Modified Screen-Printed Graphite Electrode for Determination of Carmoisine.

Food colorants are important in food selection because they improve the gastronomic appeal of foods by improving their aesthetic appeal. However, after prolonged use, many colorants turn toxic and cause medical problems. A synthetic azo-class dye called carmoisine gives meals a red color. Therefore, the carmoisine determination in food samples is of great importance from the human health control. The current work was developed to synthesis ZnO hollow quasi-spheres (ZnO HQSs) to prepare a new electrochemical carmoisine sensor that is sensitive. Field emission-scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) have been used to analyze the properties of prepared ZnO HQSs. A screen-printed graphite electrode (SPGE) surface was modified with ZnO HQSs to prepare the ZnO HQSs-SPGE sensor. For carmoisine detection, the ZnO HQSs-SPGE demonstrated an appropriate response and notable electrocatalytic activities. The carmoisine electro-oxidation signal was significantly stronger on the ZnO HQSs-SPGE surface compared to the bare SPGE. Cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CHA), and differential pulse voltammetry (DPV) have been utilized to investigate the suggested protocol. The DPV results revealed an extensive linear association between variable carmoisine concentrations and peak current that ranged from 0.08 to 190.0 µM, with a limit of detection (LOD) as narrow as 0.02 µM. The ZnO HQSs-SPGE's ability to detect carmoisine in real samples proved the sensor's practical application.

Electrochemistry of the synthetic tryptamine 5-MeO-MiPT at glassy carbon and screen-printed electrodes: A rapid and simple screening method for application in forensic analysis

5-Methoxy-N-methyl-N-isopropyltryptamine (5-MeO-MiPT), also known as moxy, is a synthetic tryptamine analogue used recreationally as a hallucinogenic drug. This work investigates the electrochemical behaviour of 5-MeO-MiPT using carbon electrodes for the first time. Although 5-MeO-MiPT showed only one irreversible oxidation process at a glassy carbon electrode, many electrochemical processes were exhibited on a graphite screen-printed electrode (SPE-Gr). The oxidation reaction of 5-MeO-MiPT on both carbon electrode surfaces involves an adsorption-controlled process with the loss of one electron and one proton. A voltammetric screening method for 5-MeO-MiPT was performed in 0.1 mol L−1 phosphate buffer solution at pH 7.0 on the SPE-Gr using differential pulse adsorptive stripping voltammetry (DPAdSV). The proposed method showed a wide linear range (0.05–30.0 µmol L−1) and a sufficiently low limit of detection (0.015 µmol L−1) for application to seized forensic samples containing 5-MeO-MiPT. Good stability of the electrochemical responses for 5-MeO-MiPT detection on SPE-Gr was obtained, using the same or different electrodes (N = 3) with a relative standard deviation of less than 4.0%. Interference studies with other drugs demonstrated that the proposed sensor is selective for electrochemical screening of 5-MeO-MiPT. In addition, 5-MeO-MiPT was identified in a biological sample of synthetic urine and in real seized samples by the proposed method and confirmed by GC-MS. The analytical performance of SPE-Gr with DPAdSV for 5-MeO-MiPT detection shows great potential as a simple, fast, and selective screening method in forensic scenarios.

Shedding light on the calculation of electrode electroactive area and heterogeneous electron transfer rate constants at graphite screen-printed electrodes

We present in detail the most known and commonly used methods for the calculation of electrode electroactive area (A) and heterogeneous electron transfer rate constants ({k}^{0}). The correct procedure for the calculation of these parameters is often disregarded due to either lack of a minimum theoretical background or oversimplification of each method’s limitations and prerequisites. The aim of this work is to provide the theoretical background as well as a detailed guide for the implementation of these measurements by impressing upon the electrochemists the parameters that need to be considered so that the obtained results are safe and useful. Using graphite screen-printed electrodes, A, and {k}^{0} were calculated with different methods and techniques. Data are compared and discussed.Graphical

Sensitive riboflavin sensing using silver nanoparticles deposited onto screen-printed electrodes via controlled-energy spark discharges

In this work, we elaborated the graphite screen-printed electrodes (SPEs) modification with metal nanoparticles formed as a result of spark discharges produced between a metal wire electrode and SPE that are connected to an Arduino board-based DC high voltage power supply. This sparking device allows, on the one hand, the toposelective formation of NPs of controlled dimensions through a direct and liquid-free approach, and on the other hand, controls the number and energy of the discharges delivered to the electrode surface during a single spark event. This way, the potential damage to the SPE surface by the action of heat evolved during the sparking process is considerably minimized compared with the standard setup in which each spark event consists of multiple electrical discharges. Data demonstrated that the sensing properties of the resulting electrodes are significantly improved compared with those achieved when conventional spark generators are employed, as demonstrated for silver-sparked SPEs that exhibit enhanced sensitivity to riboflavin. Sparked AgNp-SPEs were characterized using scanning electron microscopy and voltammetric measurements in alkaline conditions. The analytical performance of sparked AgNP-SPEs was evaluated by various electrochemical techniques. Under optimum conditions, the detection range for DPV was from 1.9 (LOQ) to 100nM riboflavin (R2=0.997), while a limit of detection (LOD, S/N 3) of 0.56nM was achieved. The analytical utility is demonstrated for the determination of riboflavin in the real matrices of B-complex pharmaceutical preparation and an energy drink.

Molybdenum Disulfide/Nickel-Metal Organic Framework Hybrid Nanosheets Based Disposable Electrochemical Sensor for Determination of 4-Aminophenol in Presence of Acetaminophen.

The toxicity of commonly used drugs, such as acetaminophen (ACAP) and its degradation-derived metabolite of 4-aminophenol (4-AP), underscores the need to achieve an effective approach in their simultaneous electrochemical determination. Hence, the present study attempts to introduce an ultra-sensitive disposable electrochemical 4-AP and ACAP sensor based on surface modification of a screen-printed graphite electrode (SPGE) with a combination of MoS2 nanosheets and a nickel-based metal organic framework (MoS2/Ni-MOF/SPGE sensor). A simple hydrothermal protocol was implemented to fabricate MoS2/Ni-MOF hybrid nanosheets, which was subsequently tested for properties using valid techniques including X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), Fourier transformed infrared spectroscopy (FTIR), and N2 adsorption-desorption isotherm. The 4-AP detection behavior on MoS2/Ni-MOF/SPGE sensor was followed by cyclic voltammetry (CV), chronoamperometry and differential pulse voltammetry (DPV). Our experimental findings on the generated sensor confirmed a broad linear dynamic range (LDR) for 4-AP from 0.1 to 600 μM with a high sensitivity of 0.0666 μA/μM and a low limit of detection (LOD) of 0.04 μM. In addition, an analysis of real specimens such as tap water sample as well as a commercial sample (acetaminophen tablets) illuminated the successful applicability of as-developed sensor in determining ACAP and 4-AP, with an impressive recovery rate.

Voltammetric determination of vitamin B6 in the presence of vitamin C based on zinc ferrite nano-particles modified screen-printed graphite electrode.

The zinc ferrite nano-particles (ZnFe2O4) modified screen-printed graphite electrode (ZnFe2O4/SPGE) was used for the voltammetric determination of vitamin B6 in real samples, using differential pulse voltammetry (DPV). It has been found that the oxidation of vitamin B6 at the surface of such an electrode occurs at a potential about 150 mV less positive compared to an unmodified screen-printed graphite electrode. After optimization, a vitamin B6 sensor with a linear range from 0.8 to 585.0 μM and a detection limit of 0.17 μM. The ZnFe2O4/SPGE sensor exhibits good resolution between the voltammetric peaks of vitamin B6 and vitamin C, making it suitable for detecting vitamin B6 in the presence of vitamin C in real samples.

Determination of the standard rate constant for soluble-soluble quasi-reversible electrochemical systems by linear sweep voltammetry: Application to the electrochemical oxidation on screen-printed graphite electrodes

Semi-analytical approach was used for modeling and establishing Linear Sweep Voltammetry (LSV) profiles in the case of quasi-reversible electrochemical reactions involving soluble species. The effects of charge transfer coefficient (α) and dimensionless kinetic rate constant (Λ) on the shape and position of voltammograms were investigated. The combined effect on the LSV responses, peak current, half peak width and peak potential was also analyzed qualitatively and quantitatively. Kinetic curves were constructed in the form of the change in the LSV characteristics as a function of (α, Λ) and then modeled by the interpolation functions. The obtained equations are an easy-to-use tool in order to calculate the heterogeneous kinetic rate constant for quasi-reversible charge transfer. Experimental-theory validation has been performed on ferrocyanide oxidation on screen-printed graphite electrodes.

A Novel Electrochemical Immunosensor Based on Anti-IgY and PLA/PEG Nanofibrous Mats Used for Allergens Detection in Farinaceous Products

The present study focuses on the first electrochemical immunosensor built with polymeric mats enriched with nanomaterials, targeting the dust mite protein, for the detection of allergens in flour sources with important implications in allergic reactions. As a proof-of-concept, we have used the Blo t 5 allergen from Blomia tropicalis (target) and established electrochemical parameters to recognize and detect the specific allergen using a polyclonal immunoglobulin (Ig) Y (probe). Detection was performed in a portable potentiostat (EmStat) using a graphite screen-printed electrode. For that, the nanofibrous mats of poly(lactic acid)/poly(ethylene glycol) (PLA/PEG), and carbon nanotubes (CNTs) were placed in contact with the surface of the electrodes. The functionalization that occurs through the deposition of the polymer was induced through the passage of current. Subsequently, the modification was validated by cyclic voltammetry (CV) readings and ferri/ferrocyanide was used as a redox indicator in CV analyses. The novel immunosensor was able to discriminate between allergen-contaminated and uncontaminated farinaceous samples. The immunosensor displays high sensitivity detecting up to 50 μg ml−1 in the calibration curve with a linear response between 5 and 500 μg ml−1. The new biosensor shows great potential in the detection of farinaceous contaminants in laboratories, food factories and in the field.

Differential Pulse Voltammetric Analysis of Hydrazine in Water Samples by Using Screen-Printed Graphite Electrode Modified with Nitrogen-Doped Hollow Carbon Spheres

The present study introduces a facile and efficient voltammetric hydrazine sensor via the modification of screen-printed graphite electrode (SPGE) with nitrogen-doped hollow carbon spheres (N-HCSs). This work is the first report of the new method of electroanalytical determination of hydrazine through N-HCSs modified SPGE. The N-HCSs fabricated through the templating approach (hard template) were characterized by Fourier transform infrared (FT-IR) spectroscopy, field emission-scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS). Cyclic voltammetry (CV), chronoamperometry (CA), and differential pulse voltammetry (DPV) were employed for electrochemical determinations. The produced N-HCSs/SPGE had an appreciable electrocatalytic capacity for the hydrazine oxidation, with the least oxidation overpotential and elevated voltammetric peak currents. The peak current of hydrazine oxidation on N-HCSs/SPGE possessed a distinct linear association with its levels (0.02–380.0 μM) under the optimized experimental circumstances, with the limit of detection (LOD) as narrow as 0.007 μM. Good stability and acceptable reproducibility were also attained on the N-HCSs/SPGE. In addition, the developed technique exhibited good selectivity toward the detection of hydrazine in the presence of some interfering species. The practical applicability of proposed sensor was successful by sensing hydrazine in water samples.