Carbon Paste Research Articles

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.

Preparation and application of a new ion-imprinted polymer for nanomolar detection of mercury(II) in environmental waters

This study introduces a novel ion-imprinted polymer for the ultrasensitive detection of mercury(II) in water. The ion-imprinted polymer was synthesized via a simple bulk polymerization process using methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross-linker, morpholine-4-carbodithioic acid phenyl ester as the chelating agent, and ammonium persulfate as the initiator. The electrochemical mercury(II) sensing capability of the ion-imprinted polymer was studied via the modification of a cost-effective carbon paste electrode. A stripping voltammetric technique was utilized to quantify the analyte ions following open-circuit enrichment. Critical experimental parameters, including the nature and concentration of the eluent, solution pH, preconcentration duration, ion-imprinted polymer dosage, sample solution volume and reduction potential, were systematically studied and optimized. Under optimal conditions, the sensor exhibited a linear response in the range of 1.0 to 240.0 nM, with a low detection limit of 0.2 nM. The sensor demonstrated remarkable selectivity against potential interfering ions, including lead(II), cadmium(II), copper(II), zinc(II), manganese(II), iron(II), magnesium(II), calcium(II), sodium(I) and cobalt(II). The practical applicability of the developed method was successfully validated through the analysis of real water samples, suggesting its potential for environmental monitoring applications.

Electroanalysis with Carbon Paste Electrodes: A Look Behind the Scientific-Research Activities of the Electroanalytical Group in Pardubice

In this article, a retrospective view of the research activities of the electroanalytical group at the University in Pardubice (UPCE) is presented, offering a concise overview on the development, continuing work, and significant achievements in electrochemical measurements with carbon paste electrodes (CPEs). At the very beginning, a brief history of the field is provided and the state-of-the-art in a global view outlined. Second, research activities with CPEs and related configurations in the former Czechoslovakia and the succeeding Czech Republic are also summarised and the respective publications cited. The introductory section ends with a historical survey of the activities of the electroanalytical group at the UPCE, characterising the individual time periods with CPEs from the mid-1980s up until now and highlighting the most important achievements and the corresponding publications. The pivotal part of the text then gathers five various examples representing some of the truly key-themes that have made electroanalysis at UPCE well-known and, at the same, distinctive. Namely, overviewed, commented, and illustrated in selected figures are (i) carbon paste mixtures with atypical binders from liquid esters, (ii) extractive pre-concentration onto the carbon paste bulk and determination of iodine, (iii) method for determination of Ag(I) ions at a CPE with extraordinary analytical performance, (iv) carbon pastes as substrates for mercury, gold, bismuth, and antimony films, and (v) recent applications of CPEs prepared from carbonaceous materials of natural origin.

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.

Development of a 1D-WO3 and CuO nanocomposite modified electrode for enhanced detection of 2,4-dichlorophenol

A common chlorinated phenol known as 2,4-dichlorophenol (2,4-DCP) was investigated electrochemically using cyclic voltammetry (CV) and square wave voltammetry (SWV). The electrochemical investigation was carried out at 1D nanostructured tungsten dioxide (WO3) and copper (II) oxide (CuO) nanocomposite-modified carbon paste electrode (CPE). The electrode's sensitivity was improved by the WO3/CuO nanocomposite, enabling investigators to more precisely measure the 2,4-DCP's electrochemical characteristics. The hydrothermal method was utilized to synthesize the WO3 NPs. The XRD, AFM, SEM, and EDS techniques were used to characterize the nanocomposite and WO3 NPs. Numerous parameters have been studied, including pH, concentration variation, scan rate variation, and accumulation time. Samples of soil, fruits, and vegetables were examined using the fabricated WO3/CuO/CPE. In the concentration range of 7.0 × 10−8 M to 2.6 × 10−7 M, a linear relationship was established along with the lower limit of detection of 0.17 × 10−8 M and the limit of quantification of 0.57 × 10−7 M. The 0.2 M phosphate buffer (PB) of pH 10.4 increased the peak current, which contributed to the WO3/CuO/CPE sensor's sensing performance and was highly sensitive with respect to 2,4-DCP detection. Anodic peak current was observed for the WO3/CuO/CPE is at -7.45 µA whereas for unmodified CPE is at -1.31 µA. According to the findings, the nanostructured WO3 and CuO nanocomposite showed exceptional sensitivity in identifying the electrochemical characteristics and reactions of 2,4-DCP.

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.

Nanoclay composites in electrochemical sensors

Nanoclays are layered structures in the nanoscale range with widespread application due to their unique properties such as swelling, cation exchange capacity, and ease of functionalisation using metals, metal oxides, and organic compounds such as carbon paste, polymers, and other biomolecules that form nanoclay composites. Nanoclay functionalisation with silver (Ag), zinc oxide (ZnO), and bimetallic silver–gold (Ag–Au) using hydrophilic and hydrophobic clays is here evaluated and discussed. The composites’ synthesis and morphological, crystallinity, and electroactive properties in comparison with pure nanoclay are also assessed. The layered structure and crystallinity of all these nanoclay composites were slightly changed. The clumped layered structures on the surface of the nanocomposites had dispersed white spots that indicated possible surface modification. The nano-films of the composites’ electroactivity were comparatively high, as seen from the increase in current in the cyclic voltammetry characterisation voltammograms and the differential pulse voltammograms of the pharmaceutical detection. Efavirenz, nevirapine, and zidovudine detection was improved by modification of the nanocomposite with human serum albumin (HSA), as shown by the higher current, thus indicating improved conductivity of the composites compared to the pure nanoclays. Applying HAS-modified nanocomposites in the analysis of efavirenz, nevirapine, and zidovudine on a glassy carbon electrode (GCE) showed good linearity and acceptable detection limits comparable to those of previous studies. Therefore, it has potential for application in pharmaceutical quality control and environmental monitoring.

Attachment of ρ-aminobenzene sulphonic acid into magnetic Fe3O4 reduced graphene oxide and its application for sensitive determination of L-tryptophan in milk and banana samples

This paper reports the attachment of p-aminobenzene sulfonic acid on the surface of magnetic Fe3O4-reduced graphene oxide. Different techniques including FTIR, UV, EIS, XRD, and SEM imaging were employed for characterization. The finding indicates the successful attachment of the p-aminobenzene sulfonic acid to the surface. The synthesized material was used to make a carbon paste electrode for the determination of the essential amino acid L-tryptophan (L-Try). EIS and CV characterization of the electrode further confirms the attachment of the acid. Of the different electrode materials used, the p-aminobenzene sulfonic acid attached magnetic Fe3O4 reduced graphene oxide showed very good electrocatalytic activity. The scan rate study showed that the electrode process is an adsorption-controlled one. The prepared electrode material gave a linear curve for 0.001 μM to 10 μM L-Try concentrations, and the limit of detection and limit of quantification were 0.26 nM and 0.78 nM, respectively. Furthermore, the electrode material was employed for the determination of L-Try in a milk and banana sample.

Water oxidation through electrocatalytic process using cobalt and nickel complexes of thiazole Schiff-base ligands

Ni(OAc)2.4H2O and CoCl2.6H2O reacted with thiazole ligands, HL and HL' (where HL= (E)-2-(((4-phenylthiazol-2-yl)imino)methyl)phenol and HL'= (Z)-2-(2-benzylidenehydrazinyl)-4-phenylthiazole, in ethanol to create new mononuclear Co(II) and Ni(II) complexes, CoL2, NiL2, CoL'2, and NiL'2 (1-4). X-ray diffraction analysis, spectroscopic, and electrochemical methods were used to study the complexes. A carbon paste electrode that had been modified by complexes 1-4 was used as the working electrode in a three-electrode setup to test the complexes' ability in water oxidation reaction at pH 13. The linear sweep voltammetry (LSV) curves showed that complexes 3 and 2 have much greater activity and only require the overpotential of 570 and 690 mV ʋs. RHE at a current density of 10 mA/cm2 with Tafel slopes of 86.92 and 94.19 mVdec−1 respectively in an alkaline solution. In addition, the amperometry tests exhibited brilliant stability for water oxidation by CPE-complex 3 and CPE-complex 2 under electrochemical conditions at pH 13. Although X-ray diffraction patterns did not display a crystalline structure, the scanning electron microscopy images displayed that cobalt oxide and nickel oxide in an alkaline condition are proper catalysts for water oxidation reaction on the surface of the modified electrode.

A highly sensitive and selective molecularly imprinted sensor for the determination of atorvastatin

In this study, we developed a highly sensitive carbon paste sensor that combines a molecularly imprinted polymer (MIP) with specific recognition capabilities to monitor atorvastatin (ATV). In the MIP synthesis, designed especially for ATV, ethylene glycol dimethacrylate (EGDMA) was utilized as a cross-linking monomer and methacrylic acid (MAA) as a functional monomer. This non-covalent method made use of polymerization by free radicals. After that, this MIP was added to a carbon paste electrode (CPE), which served as both a selective detection element and a preconcentration agent for ATV analysis. The improved CPE was characterized using scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). To investigate ATV, the anodic peak signal was assessed using square wave stripping voltammetry (SWSV).The calibration curve exhibited two linear regions encompassing dosages from 0.005 to 1 µM and 1 to 20 µM, with a 1.5 nM calculated detection limit. The designed MIP electrode was successfully utilized to assess ATV in tablet and human blood serum samples, demonstrating its usefulness in practical analysis.

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.

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.

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.

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.

Electrostatically self-assembled magnetized MXene/copper ferrite nanospheres hybrids: Evaluation of molecularly imprinted electrochemical sensor for the quercetin antioxidant supplement

Quercetin, a bioflavonoid with significant biological activities, is beneficial for health. Herein, a pioneering molecularly imprinted electrochemical sensor utilizing an MXene/CuFe2O4 magnetic nanosphere hybrid was developed for the first time to detect quercetin ultra-sensitively. CuFe2O4 nanospheres (average 189 nm) were synthesized and combined with MXene sheets, then electrostatically deposited onto a magnetic carbon paste electrode. A functional monomer was then electropolymerized onto this hybrid-modified electrode to form an imprinted polymeric layer, tailored for quercetin binding. Characterizations confirmed the morphological and magnetic properties of the materials. The sensor’s response factors were optimized, achieving a low detection limit of 1.6 nM and two linear ranges (0.005–0.7 μM and 0.7–10 μM). The sensor showed excellent stability, repeatability, reproducibility, and selectivity, and was successfully used to quantify quercetin in dietary supplements.

Utilization of azamacrocyclic ionophores as recognition elements for the potentiometric determination of gallic acid in various matrices

Gallic acid is a naturally occurring low molecular weight triphenolic molecule identified as a potent antioxidant, protecting against various types of reactive species and non-radicals. Three novel carbon paste electrodes were developed for the potentiometric determination of gallic acid. Azamacrocyclic ionophors; cyclen, hexacyclen, and kryptofix-22 were utilized as recognition ionophores separately. A multi-walled carbon nanotubes/titanium oxide nanocomposite was employed as the ion-to-electron transducer in the designed sensors. The prepared transducer was characterized by FT-IR and TEM. Molecular docking was implemented to study the recognition mechanism between these ionophores and the gallic acid molecule. It revealed promising binding interactions between gallic acid and the three recognition ionophores, especially hexacyclen and Kryptofix-22. In studying the potentiometric response of the proposed sensors, they exhibited high stability, sensitivity, accuracy, and precision in the quantitation of gallic acid. Gallic acid can be accurately quantified over the linearity range of 1 × 10−1–1 × 10−3 M, 1 × 10−2–1 × 10−6 M, and 1 × 10−2–1 × 10−6 M with a Limit of detection (LOD) 4 × 10−4 M, 3 × 10−7 M, and 7 × 10−7 M, for CPE1, CPE 2 and CPE 3, respectively. The electrodes showed high efficiency in determining gallic acid in Krameria lappacea root alcoholic extract, black tea, green tea, and human plasma without sophisticated pretreatment steps.

A voltammetric sensor based on CuCo2O4 nanorods and ionic liquid for determination of sunset yellow

In this study, we report the electrochemical detection of sunset yellow (SY) at the surface of a carbon paste electrode (CPE) modified with CuCo2O4 nanorods (NRs) and an ionic liquid (IL). The electrochemical behavior of sunset yellow at the modified electrode was investigated using linear sweep voltammetry, differential pulse voltammetry and chrono­amperometry techniques. The CuCo2O4 NRs/IL/CPE sensor exhibited good performance and favorable electrochemical response for the electrochemical reaction of SY in a 0.1 M phosphate buffer solution at pH 7.0. The results showed a linear electrochemical response to SY within the concentration range of 0.2 to 160.0 μM, with a detection limit of 0.06 μM. In addition, The CuCo2O4 NRs/IL/CPE sensor demonstrated good ability for SY determination in real samples.

Design of high-performance electrochemical sensor based on SnS2 nanoplates and ionic liquid-modified carbon paste electrode for determination of hydrazine in water samples

Designing effective and accurate analytical techniques to determine hydrazine is essential for preserving the environment. Herein, an electrochemical sensor based on a carbon paste electrode (CPE) modified with SnS2 nanoplates (SnS2NPs) and ionic liquid (IL) was presented for determination of hydrazine in water samples. The SnS2NPs were synthesized using the hydrothermal method and characterized through field emission scanning electron microscope, Fourier transform infrared spectrometer and energy dispersive spectroscopy. The use of cyclic voltammetry in electrochemical investigations has shown that incorporating IL and SnS2NPs in an electrochemical sensor significantly improves its efficiency. These results in a considerable increase in the oxidation peak current and a decrease in the oxidation peak potential of hydrazine compared to an unmodified CPE. The method of differential pulse voltammetry was utilized to accurately measure the quantity of hydrazine. The SnS2NPs/ILCPE showed improved sensing capabilities, resulting in a noticeable sensitivity of 0.0747 µA/µM and a low limit of detection of 0.05 µM for a broad linear range of hydrazine concentration from 0.08 µM to 450.0 µM. In addition, the SnS2NPs/ILCPE sensor was successfully utilized to measure the amount of hydrazine present in water samples, with a recovery range of 96.0 to 104.4 %. The relative standard deviation was found to be lower than 3.6 % (n = 5), indicating that the developed sensor is suitable for accurately determining hydrazine in water samples with high sensitivity.

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).