Modified Carbon Paste Electrode Research Articles

Metal–Organic Framework-Derived CeO2/Gold Nanospheres in a Highly Sensitive Electrochemical Sensor for Uric Acid Quantification in Milk

In this work, CeBTC (a cerium(III) 1,3,5-benzene-tricarboxylate), was used as a precursor for obtaining CeO2 nanoparticles (nanoceria) with better sensor performances than CeO2 nanoparticles synthesized by the solvothermal method. Metal–organic framework-derived nanoceria (MOFdNC) were functionalized with spheric gold nanoparticles (AuNPs) to further improve non-enzymatic electrode material for highly sensitive detection of prominent biocompound uric acid (UA) at this modified carbon paste electrode (MOFdNC/AuNPs&CPE). X-ray powder diffraction (XRPD) and transmission electron microscopy (TEM) analysis were used for morphological structure characterization of the obtained nanostructures. Cyclic voltammetry and electrochemical impedance spectroscopy, both in an [Fe(CN)6]3−/4− redox system and uric acid standard solutions, were used for the characterization of material electrocatalytic performances, the selection of optimal electrode modifier, and the estimation of nature and kinetic parameters of the electrode process. Square-wave voltammetry (SWV) was chosen, and the optimal parameters of technique and experimental conditions were established for determining uric acid over MOFdNC/AuNPs&CPE. Together with the development of the sensor, the detection procedure was optimized with the following analytical parameters: linear operating ranges of 0.05 to 1 µM and 1 to 50 µM and a detection limit of 0.011 µM, with outstanding repeatability, reproducibility, and stability of the sensor surface. Anti-interference experiments yielded a stable and nearly unchanged current response with negligible or no change in peak potential. After minor sample pretreatment, the proposed electrode was successfully applied for the quantification of UA in milk.

A New Modified Carbon Paste Electrode for Selective Determination of Chromium(III) in Pharmaceutical Drugs and Food Samples

Background and Objective: This study presents a novel potentiometric method for the precise, accurate, selective, and rapid determination of Cr(III) ion concentration in different samples. Methods: A new ionophore, namely macrocyclic tetramide ionophore (MCTA), was synthesized through an inexpensive and straightforward approach, yielding a high-quality product. The (MCTA) ionophore was utilized as the active center in the preparation of modified carbon paste electrodes (MCPEs) to quantify the Cr(III) ion. The paste was made by adding graphite, MCTA, and plasticizer and mixing them in varying weight percent ratios. Results: The proposed electrodes, I and II, exhibited a trivalent Nernstian response of 20.029 ±0.57 and 20.3±0.56 mV decade-1 , respectively, with linearity of 1.0x10-7 – 1.0x10-2 and 1.0x10-5 – 1.0x10- 2 mol L-1 . Electrodes I and II were examined for their pH, response time, and thermal stability. In comparison to other mono-, bi-, and trivalent cations, starch, and sugars, the electrodes demonstrated a high degree of selectivity for Cr(III). The modified electrodes were used to determine the concentration of Cr(III) in various real samples, including drug tablets, juice extractions, and tap water, with acceptable recovery values. Conclusion: The results were compared with those obtained using the previously reported method, with no significant difference observed between them, as indicated by the F and t-test values. The data showed good accuracy and precision, as well as a high percentage of recovery. The adsorption capacity of the MCTA ionophore towards Cr(III) ions was also examined.

Efficient electrochemical determination of Sudan I in food samples based on modified electrode by using Ni-Fe layered double hydroxide nanosheets and ionic liquid

Sudan I, is one of the commonly used azo dyes in food samples, which has shown adverse effects on human health. Therefore, determining the level of Sudan I in food samples can be very effective in ensuring food safety and protecting human health. In this study, an electrochemical sensing platform was designed using Ni-Fe layered double hydroxide nanosheets and ionic liquid modified carbon paste electrode (Ni-Fe LDH/ILCPE) which was utilized to determine Sudan I. Comparison of cyclic voltammograms of Sudan I on the unmodified CPE and Ni-Fe LDH/ILCPE showed that, the higher oxidation currents were obtained on the surface of the Ni-Fe LDH/ILCPE, indicating that the modified CPE owns significant surface improvement effects and good electrochemical performance in detecting Sudan I. Under optimized conditions, the developed Ni-Fe LDH/ILCPE sensor demonstrated a linear relationship between the voltammetric response and Sudan I concentrations from 0.03 µM to 510.0 µM with a low detection limit (LOD) of 0.01 µM based on S/N = 3.0. Additionally, the Ni-Fe LDH/ILCPE platform exhibits high accuracy, with a recovery of 96.4 % to 104.1 % for Sudan I determination in food samples including Ketchup and Chilli powder, which implies that it will be a potential detection method for Sudan I detection.

Producing Activated Biochar from the Reuse of Discarded Coffee Grounds with Enhanced Adsorptive Features Explored Towards the Stripping Voltammetric Sensing of Copper (II)

AbstractThis work aims to allocate coffee grounds waste to the production of biochar from pyrolysis under different temperatures (350 °C and 500 °C), to add value to it. The resulting materials were characterized by immediate, elemental, thermogravimetric analysis, SEM, FT‐IR, XRD and Raman spectroscopy. Additionally, the need to activate the biochar produced for the desired use was evaluated. The obtained biochars were applied in electroanalysis in the manufacture of modified carbon paste electrodes. This choice was made due to the possibility of reaching a high sensitivity towards the determination of Cu2+ ions. The differential pulse adsorptive anodic stripping voltammetry technique was applied to perform the Cu2+ determination and, in this case, several parameters were optimized, including biochar’ percentage, pH of pre‐accumulation step and reduction/stripping step, pre‐accumulation time, potential and time of reduction of adsorbed‐Cu2+. From this, the proposed modified electrode showed a linear voltammetric response towards Cu2+ in the range of 66.1 to 3997.3 ppb, with a limit of detection of 31.8 ppb, in addition to having been satisfactorily applied in the analysis of water samples (recoveries close to 100 %). Thus, demonstrating the potential for reuse of discarded coffee grounds for the preparation of activated biochar with outstanding electrochemical performance.

Nanohybrids of B- and N-codoped reduced graphene oxide/CeO2–Co3O4 nanocomposite for efficient water oxidation

Transition metal oxides are well known as highly active and durable catalysts for the oxygen evolution reaction (OER). In this work, to enhance the electrocatalytic activity of CeO2 nanostructure in the water oxidation reaction, CeO2/Co3O4 and boron-nitrogen co-doped reduced graphene oxide incorporated (B,N-rGO) into CeO2/Co3O4 with a weight ratio of 3:1 of nanoparticles to graphene oxide were synthesized using co-precipitation and hydrothermal methods, respectively. The prepared materials were studied in detail regarding their crystal structure and morphological properties. The as-prepared materials were used as modified carbon paste electrodes for electrochemical water oxidation in an alkaline solution. The results showed that incorporating graphene oxide network into the nanoparticles structure enhances their OER performance. The material based on CeO2/Co3O4@B,N-rGO hybrid nanocomposite showed excellent OER activity with an overpotential of 410@10 mA cm−2, which is 240 and 140 mV less than that of the single CeO2 and CeO2/Co3O4 samples. Also, CeO2/Co3O4@B,N-rGO displayed the lowest Tafel slope and charge transfer resistance among the other catalysts. Moreover, the proposed catalyst displayed high stability and durability during OER. The enhanced OER performance of the CeO2/Co3O4@B,N-rGO is attributed to several catalytically active sites created by B and N doped rGO in the nanocomposite structure. The high performance of this catalyst results from the synergy of combining CeO2/Co3O4 nanoparticles with a three-dimensional co-doped rGO network.

Flow injection analysis of hydroquinone using amperometric sensor modified with nanomaterials

Modified carbon paste electrodes (CPE) have been widely used in diverse applications, such as environmental, food, and pharmaceutical analysis, among other applications. In this work, the development of an amperometric sensor modified with functionalized multi-walled carbon nanotubes (CNT) and HY-type zeolite (ZEO) is reported for the analysis of hydroquinone (HQ) in pharmaceuticals. Practical and theoretical studies were carried out regarding the modifiers used. No chemical bond was observed between the modifiers and the analyte, such as HQ and CNT. It is likely that dynamic interactions governed by surface adsorption phenomena, rather than covalent bonding, are occurring. Furthermore, the contribution of modifiers to the improvement of the analytical peak current was elucidated through characterization studies, such as electrochemical impedance spectroscopy. These experiments revealed a 147-fold decrease in charge transfer resistance when CPE was modified with ZEO and CNT, which is likely due to an enhancement in electron transfer. A sample rate of 100 injections per hour, and the limit of quantification (LQ) of 8.99 x 10-7 mol/L were achieved during the oxidation of HQ using amperometry in association with flow injection analysis (FIA). The sensitivity of the proposed sensor was of 0.0186 mol/L cm−2. Determinations of pharmaceutical samples were in good agreement with results obtained by High Performance Liquid Chromatography.

TiO2 intercalated MWCNTs nanocomposite sensor for the detection and quantification of 5-Fluorouracil

The present analysis deals with the fabrication of novel electrochemical sensing platforms for the determination of the anti-cancer drug 5-Fluorouracil (5-FLU). Multiwalled carbon nanotubes/titanium dioxide nanoparticles (TiO2·MWCNTs) modified carbon paste electrodes were constructed and used to quantify 5-FLU in pH 7.0. TiO2·MWCNTs nanocomposite reveals a non-uniform distribution of agglomerated TiO2 nanoparticles over the smooth surface of MWCNTs At the TiO2∙MWCNTs/CPE, the 5-FLU molecule underwent an irreversible electro-oxidation process. The proposed electrode platform exhibited a high catalytic effect for the 5-FLU. The TiO2∙MWCNTs/CPE sensor shows the detection limits of 2.7nM for 5-FLU with sensitivity of 82.15µA·µM−1·cm−2. The sensor was employed to detect the desired drug moiety in the urine samples of pharmaceutical drugs along with spiked water and soil samples; the good recovery values demonstrating the applicability and selectivity of the sensor were supported by excipient interference investigation. Thus, the developed sensors and method makes them a promising alternative for future research to determine other bio-active molecules in pharmaceutical and clinical samples.

Electrochemical Determination of Cysteine Using a 2-(2,5-Dihydroxy-Phenyl)-Naphtho[1,2-d] Oxazole-5-Sulfonic Acid (DHPNOS) and Cerium Oxide Nanoparticle (CeO2NP) Composite Carbon Paste Electrode (CPE)

An electrochemical sensor for the electrocatalytic oxidation of cysteine was designed based upon a 2-(2,5-dihydroxy-phenyl)-naphtho[1,2-d] oxazole-5-sulfonic acid (DHPNOS) and cerium oxide nanoparticle (CN) modified carbon paste electrode (CPE). An investigation of the redox properties of this modified electrode indicates a reduction in oxidative overvoltage and an intense increase in the analytical current. The pH, modifier, and nanoparticles were optimized to 7, 4% weight percent, and 5% weight percent, respectively. The apparent charge transfer rate constant (ks) and transfer coefficient for electron transfer between modifier and electrode were 2.776 s−1 and 0.47, respectively. Using differential pulse voltammetry, a linear range from 1 to40 µM with a detection limit of 0.33 µM was observed in phosphate buffer (pH 7.0). This work introduces a simple approach for selective determination of L-cysteine in the presence of uric acid. Also, based on chronoamperometry, the diffusion coefficient was determined to be 2.61 × 10−5 cm2 s−1. The effect of interferences on L-cysteine peak current were studied. The repeatability and reproducibility of the designed sensor were also measured with relative standard deviation values of 1.00% and 4.45%, respectively. The constructed sensor was employed for the determination of L-cysteine in acetylcysteine tablets.

Electrochemical Oxidation of Glutathione in the Presence of Tryptophan at Carbon Paste Electrode Modified with Ni-Zn-Metal-Organic Frameworks/Graphene Oxide and Ferrocene Derivative

Glutathione (GSH) plays a vital physiological role as it is implicated in the progression and pathogenesis of a wide range of medical conditions, including diabetes, various types of cancer, and Parkinson’s disease. Due to the fundamental physiological importance of GSHand its relevance to numerous medical conditions, there is a clear need to develop simple, rapid, and cost-effective analytical methods. These methods could significantly aid in clinical diagnostics and guide the optimization of treatment approaches. This work reports the synthesis and characterization of a Ni-Zn-metal-organic framework/graphene oxide (Ni-Zn-MOF/GO) composite material, and its application as a modifier for a carbon paste electrode (CPE) in the electrochemical detection of GSH. The Ni-Zn-MOF/GO/ferrocene (FC)-modified CPE (Ni-Zn-MOF/GO/FC/CPE) was developed for this purpose. The Ni-Zn-MOF/GO/FC/CPE electrochemical sensor exhibited two linear response ranges for GSH: from 0.01–90.0 μM, and from 90.0–800.0 μM, with a detection limit estimated to be 0.003 μM. Importantly, Ni-Zn-MOF/GO/FC/CPE was shown to be suitable for the determination of GSH in the presence of tryptophan in real samples, such as human blood, GSH tablet and urine samples. The results highlight the potential of the Ni-Zn-MOF/GO/FC/CPE electrochemical sensor as a reliable and sensitive platform for the detection of GSH.

Development of ZnO-Pd/Bi2O3 nanocomposite modified carbon paste electrode as a sensor for the simultaneous determination of piroxicam and naproxen

For the first time, an electrochemical sensor was introduced by synthesizing a ZnO-Pd/Bi2O3 nanocomposite into a carbon paste electrode (CPE). The sensor was utilized to simultaneously measure both piroxicam (PIR) and naproxen (NAP). The synthesized nanocomposite’s characteristics were scrutinized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). Chronoamperometry, cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry (DPV) techniques were applied to study the electrochemical behavior of the modified electrode in aqueous solutions. A significant increase in the peak current response of PIR and NAP was observed with the ZnO-Pd/Bi2O3 nanocomposite modified carbon paste electrode (ZnO-Pd/Bi2O3/CPE) compared to the bare CPE. Through the DPV technique, ZnO-Pd/Bi2O3/CPE achieved the linear range of 0.3 to 1200 μM with the limit of detection (LOD) of 0.092 μM for PIR and the linear range of 0.5 to 900 μM with the LOD of 0.155 μM for NAP. Also, the limit of quantification (LOQ) for PIR and NAP has been calculated as 0.305 and 0.514 μM, respectively. The comprehensive analysis of real samples demonstrated the precise detection of PIR and NAP in wastewater, tablets, urine, and tap water, highlighting the broad applicability and reliability of the developed sensor in diverse real-world scenarios.

Sustainable Synthesis of Novel Calcium Magnesium Nanoferrites for Biomolecules Sensing and its Antimicrobial Properties

AbstractSustainable synthesis of novel Calcium magnesium ferrite nanomaterial was carried out in this work using aloe vera plant extract as a fuel for the combustion method. Structural characterizations of the synthesized material shows the crystallite size∼ 14 nm with cubic structure and chemical bonds between Ca−O and Fe−O. Porous nature and agglomerated particles were observed in morphological analysis. Modified carbon paste, glassy carbon and screen printed electrodes were prepared using the synthesized nanomaterial for biomolecules sensing using cyclic voltammetry technique. Therefore, the present green synthesized CMF nanoparticles modified carbon paste electrode shows significantly high sensitivity and hence it can be used as a sensor for biomedical application. Employing the agar disc diffusion technique, the antimicrobial activity of the synthesized nanoparticles was ascertained. C against the pathogens like Pseudomonas spp., E coli, and Staphylococcus spp.

Green electrochemical sensor based on ZnO@α-Fe2O3 NPs modified carbon paste electrode for sensitive voltammetric determination of the FDA-approved Anti-COVID-19 medication baricitinib

In this study, we developed an electrochemical sensor for the sensitive voltammetric determination of Baricitinib (BCT), a recently FDA-approved medication for curing COVID-19. Voltammetric measurements were employed using a carbon paste electrode modified with zinc oxide and iron oxide nanoparticles (ZnO/α-Fe2O3-NPs/CPE). The composition of the fabricated electrode was optimized, and the best sensitivity was achieved by utilizing 5% of ZnO/α-Fe2O3-NPs, which maximized the electroactive surface area. The final optimized electrode was electrochemically and physicochemically characterized by exploiting the following techniques: X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). All experimental parameters, including the pH and scan rate, have been studied and optimized. The proposed sensor was successfully employed for BCT analysis by square wave voltammetry (SWV), and the attained linear dynamic range was (8.0 × 10−8 – 1.0 × 10−6 mol L−1), and the estimated limit of detection (LOD) and limit of quantitation (LOQ) were 1.799 × 10−8 mol L−1 and 5.453 × 10−8 mol L−1, respectively. The suggested electrochemical methodology was effectively utilized to determine BCT with satisfactory percentage recoveries in pharmaceutical preparation (99.69% ± 0.73) and human plasma samples. The developed approach underwent validation and was determined to be reproducible (RSD = 0.75%) and accurate (99.68% ± 0.76) following the ICH recommendations. The greenness of the established electrochemical protocol was assessed utilizing the Analytical Eco-Scale and Analytical GREEnness Metric Approach (AGREE).

A cutting edge potentiometric determination of baricitinib in synthetic wastewater and in tablet dosage form using modified carbon paste ion-selective membrane

After the recent hit of COVID-19, many drugs were successively administered to save patients’ lives and those drugs reached aquatic sources, one of those drugs was Baricitinib. Driven by the current situation, a potentiometric technique using an ion-selective membrane (ISM) recipe drop cast on a modified carbon paste electrode was optimized for the superior determination of Baricitinib (BAR). The molecular docking was customized to optimize the proper ionophores incorporated in the ISM, revealing that beta-cyclodextrin (β-CD) is the most compatible ionophore with the studied drug. A multivariate optimization experimental design was employed to optimize the best experimental condition for the analytical method. To this end; dual nanoparticles (multi-walled carbon nanotubes and copper oxide nanoparticles) were incorporated in the carbon paste electrode, and the ISM recipe was enriched with β-CD and cation-exchanger (phosphotungstic acid) in a polyvinylchloride matrix plasticized with dibutyl phthalate. A Nernstian slope equal to 19.97 mV/decade with a linearity range of 7.99 × 10−7–1.00 × 10−3 M was obtained. The validated sensor exhibited good recovery when used to determine the studied drug in synthetic wastewater and tablet dosage form. The greenness of the method was evaluated using the Complementary Green Analytical Procedure Index and Blue Applicability Grade Index.

Green Synthesis of Clay/rGO Composite for Sensitive Detection of Para Nitrophenol in the Environment

AbstractNitrophenols (e. g., para nitrophenol), although they have beneficial properties, their residuals are injurious to the environment owing to their high lethal potential for many categories of nature (e. g. animals, humans, plants, etc.), which require their monitoring. In this paper, a new Clay/green reduced graphene oxide composite (Clay/rGO) was efficaciously synthesized and utilized as an excellent modifier for carbon paste electrode (CPE) for the electro‐analytical determination of paranitrophenol (PNØ). The electrochemical futures and reduction of PNØ at the surface of the as‐prepared Clay/rGO˧CPE have been executed using DPV differential pulse voltammetry (DPV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The use of the EIS provided that the Clay/rGO˧CPE facilitate the electron exchange process. By using the DPV technique in phosphate buffer (PB) under biological pH (7) (PB_7) the prepared monitor exhibited an excellent linearity relationship in the concentration ranges from 1.0 to 1000.0 μM with a detection limit (DL=3×σ/P) of 0.16 μM and a quantification limit of (QL=10×σ/P) of 0.54 μM. The Clay/rGO˧CPE offered high selectivity and a satisfactory concert in the electroanalytical sensing of PNØ in wastewater sample.

Fe-doped WO3-Modified sensor for the improved electrochemical detection of curcumin

In this study, an iron-doped tungsten oxide (Fe-WO3) nanomaterialwas synthesizedand utilized to modify carbon paste electrodes for the identification of the bioactive ingredient curcumin (CUM). Turmeric contains a bioactive compound called curcumin, which is yellow and has various potential biological applications, such as being an anti-carcinogenic, anti-inflammatory, and antioxidant agent. The Fe-WO3 nanomaterial underwent characterization through SEM, XRD, and EDS techniques. The electrochemical performance of CUM was inquired using square wave and cyclic voltammetry methods. During catalytic oxidation, the Fe-WO3 working electrode assembly showed faster electron transport than the bare CPE. Investigations havebeen conductedinto the kinetics of oxidation, and the developed sensor demonstrated an excellent linear detection range (5 μM to 60 μM), a decreased limit of detection (6.2 × 10−8 M), and a limit of quantification under optimal conditions (20.7 × 10−8 M).The numbers of electrons transmitted, the heterogeneous rate constant, the electron transfer coefficient, and the electrochemical oxidation were all measured. The results from the examination of CUM in actual samples using the devised Fe-doped WO3 modified electrode were good. Additionally, it showed a considerable increase in the curcumin peak current concerning responsively, specificity, and reliability for curcumin analysis.

Exploring the diverse applications of sol–gel synthesized CaO:MgAl2O4 nanocomposite: morphological, photocatalytic, and electrochemical perspectives

A nanocomposite of CaO:MgAl2O4 was synthesized through a straightforward and cost-effective sol–gel method. The investigation of the novel CaO:MgAl2O4 nanocomposite encompassed an examination of its morphological and structural alterations, as well as an exploration of its photocatalytic activities and electrochemical characteristics. XRD analysis revealed a nanocomposite size of 24.15 nm. The band gap, determined through UV studies, was found to be 3.83 eV, and scanning electron microscopy (SEM) illustrated flake-like morphological changes in the CaO:MgAl2O4 samples. TEM, HRTEM, and SAED studies of a CaO:MgAl2O4 nanocomposite would reveal important details about its morphology, crystallography, and nanostructure. Photocatalytic activity was quantified by studying the degradation of Acid Red-88 (AR-88) dye in a deionized solution, achieving a 70% dye degradation under UV irradiation in 120 min. Plant growth examinations were carried out using dye degraded water to test its suitability for agriculture. The electrochemical energy storage and sensing applications of the prepared nanocomposite were examined using CaO:MgAl2O4 modified carbon paste electrode through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). In conclusion, the synthesized CaO:MgAl2O4 nanocomposite demonstrated promising morphological and structural characteristics, efficient photocatalytic activity, and potential applications in electrochemical energy storage, highlighting its versatility for various technological and environmental applications.Graphical abstract

Eco-friendly Synthesis of Silver-Doped Reduced Graphene Oxide Nanocomposite, The Characterization, and Evaluation of Electrochemical Activity

In this study, Orobanche aegyptiaca Pers., which is an important holoparasite plant, was used for green synthesis of reduced graphene oxide silver nanocomposites (rGO-AgNCs). The obtained rGO-AgNCs were characterizated using UV–Vis spectroscopy, Fourier transformation infrared spectroscopy (FT-IR), X-Ray diffractiometer (XRD), Scanning electron microscope (SEM), Transmission electron microscope (TEM), and X-Ray photoelectron spectroscopy (XPS). The synthesized rGO-AgNCs structure were used to modify carbon paste electrode (rGO-AgNCs@CPE) for electrochemical determination of metronidazole (MNZ). It was observed that the obtained rGO-AgNCs@CPE showed higher sensitivity in MNZ determination than the unmodified CPE, and DPV measurements showed a low detection limit of 0.039 μM over a linear concentration range of 5–300 μM. Real sample analysis of the proposed sensor shows that it responds well in MNZ analysis of human urine.

Determination of methotrexate using carbon paste electrode modified with ionic liquid/Ni-Co layered double hydroxide nanosheets as a voltammetric sensor.

Methotrexate (MTX) is a widely used anti-cancer drug, but its overuse can lead to significant side effects. Therefore, it is very vital to design simple and sensitive analytical methods for its determination. In this work, an electrochemical sensor was prepared based on an ionic liquid (IL)/Ni-Co layered double hydroxide nanosheets (Ni-Co-LDH)-modified carbon paste electrode IL/Ni-Co-LDH/CPE. Cyclic voltammetry, differential pulse voltammetry, and chronoamperometry methods were applied to evaluate the performance of the designed sensor for MTX determination. The IL/Ni-Co-LDH/CPE sensor exhibits a linear relationship between the peak current of the differential pulse voltammetry and MTX concentrations in the linear dynamic range of 0.02 to 140.0 μM, with a detection limit of 0.006 μM. The IL/Ni-Co-LDH/CPE sensor exhibited relative standard deviation values between 1.7 to 3.7 % for recovery tests on real samples, indicating the precision of the method. The designed sensor with cost-effective and good performance could be valuable for therapeutic drug monitoring and clinical diagnostics.

Amperometric Determination of Dopamine and Ascorbic Acid with a Carbon Paste‐Yttrium Oxide Electrode

AbstractThis report presents a new application for yttrium oxide (YOX) in the modification of carbon paste electrodes with excellent electroactivity for the independent detection of dopamine (DA) and ascorbic acid (AA). The surface of the YOX‐modified electrode was characterized with SEM and EDS. The electroactive properties of DP and AA were studied with cyclic voltammetry (CV), square wave voltammetry (SWV) and amperometry (Am). The activity of DA and AA increased by more than 100 % when YOX/CPE was used, which allowed us to obtain detection limits of 0.04 and 0.06 μmol/L for DA and AA, respectively. The usefulness of YOX/CPE was tested with real human urine, fresh orange juice and vitamin C tablets, and the results were acceptable.

Effect of cytosine and adenine on graphene oxide for the sensing of dopamine: Electrochemical and theoretical studies

In this work, the electrochemical interaction between dopamine and cytosine/adenine on the graphene oxide (GO) is elucidated by quantum chemical simulation methods. Initially, GO, cytosine-functionalized GO (CGO), and adenine-functionalized GO (AGO) were prepared, and then utilized for the carbon paste electrode (CPE) modification. The as-prepared CGO-modified CPE (CGCPE) and AGO-modified CPE (AGCPE) were applied for the electrochemical sensing of dopamine (DA), and the obtained consequences illustrate the improved sensitivity of modified CPEs (MCPEs) compared to bare CPE (BCPE). Here, applied theoretical concepts based on analytical Fukui functions and frontier molecular orbitals (FMO) for cytosine and adenine functional groups in order to find active sites, and explained with evidence for the detection of DA by enhancing sensitivity. Moreover, the AGCPE has been shown higher electrochemical response compared to CGCPE for the detection of DA, and this result also agreed with theoretically from Global electron transfer results. The MCPEs were also utilized to examine the different electrochemical parameters and determine the DA concentration in the nanomolar range. The detection limit for CGCPE and AGCPE was found to be 9 nm and 7 nm, respectively.