Britton-Robinson Buffer Solution Research Articles

Development of an electroanalytical methodology for the identification and quantification of cocaine in samples seized using a carbon paste electrode modified with multi-walled carbon nanotubes

Among the drugs of abuse, cocaine (COC) is the second most commonly used worldwide due to its stimulating and psychoactive effects. Currently, this drug is classified, according to the World Drug Report (WDR), as an illicit substance and is frequently seized by law enforcement agencies. Additionally, it can cause social problems due to its abusive use. This study describes the development of an electroanalytical methodology using square wave voltammetry (SWV) associated with a single electrode of carbon paste modified with 10 % MWCNTs (multi-walled carbon nanotubes) to quantify COC in seized samples containing up to 20 % cocaine (low purity index) in the state of Espírito Santo (Brazil). SWV parameters, including Es = 10 mV, a = 30 mV, and f = 15 Hz, were optimized utilizing a Britton-Robinson buffer solution of 0.1 mol/L (pH 10) as a supporting electrolyte through the implementation of experimental design (CCD). COC showed an oxidation peak at approximately 1.0 V, with low limits of quantification and detection (1.90 × 10−6 mol/L and 5.75 × 10−7 mol/L, respectively), in the linear range from 2.36 × 10−6 mol/L to 1.38 × 10−5 mol/L, with the proposed methodology. Thus, this research develops a fast and low-cost technique in favor of the police, allowing the R2 = 99 %. The results obtained in the intraday calibration curves present a relatively low standard deviation (RSD < 8 %), indicating a good repetition of the value production of an electrode for less than US$ 1.42 per analysis.

Two green and sensitive spectrofluorimetric approaches for determination of Ambroxol and guaifenesin in their single and combined pharmaceutical formulations.

Ambroxol hydrochloride (AMX) and guaifenesin (GFN) are approved drugs utilized to treat coughs through their potent mucolytic and expectorant properties. Due to their massive, combined administration in many illnesses, there is a persistent need for their concurrent estimation in different pharmaceutical formulations. Two sensitive, environmentally friendly spectrofluorimetric methods were developed. AMX was determined using the first method (I) without interference from GFN. This method depends on the quenching of Erythrosine B (EB) native fluorescence at 552 nm after excitation at 527 nm due to the formation of a non-fluorescent AMX-EB ion-pair complex in Britton-Robinson buffer (BRB) solution pH (3.5). The concentration plot is linear over the 0.25-5.0μg/mL range, with a mean percent found value of 99.74%. Method (II) depends on measuring the native fluorescence of aqueous GFN solution at two analytical wavelengths, either 300 or 600 nm, after excitation at 274 nm. Relative fluorescence intensity (RFI)-concentration plots are linear over the ranges of 0.02-0.5 and 0.1-2.0μg/ml, with mean percent found at 99.96% and 99.91% at dual wavelengths, respectively. The proposed methods were successfully applied to assay both drugs in raw materials and different single and combined pharmaceutical formulations. These methods have been thoroughly validated following International Committee on Harmonisation (ICH) guidelines. National Environmental Methods Index, Analytical Eco-Scale, and Green Analytical Procedure Index were used to prove greenness, thereby enhancing their applicability. The proposed techniques provide straightforward, precise, and cost-effective solutions for routine formulation analysis in quality control laboratories.

Electrochemical determination of riboflavin in pharmaceuticals using unmodified screen printed carbon electrodes.

In this study, we have devised an efficient and rapid approach to detect riboflavin (also known as Vitamin B2 or VB2) utilizing an unaltered screen-printed carbon electrode (SPCE). The unmodified screen-printed electrodes are created within the laboratory, where carbon ink is applied to a ceramic substrate. All experiments pertaining to the investigation of electrochemical behavior and the fine-tuning of crucial experimental parameters were conducted through cyclic voltammetry (CV). For quantitative assessments, square wave voltammetry (SWV) was employed. The findings indicate that unaltered SPCEs exhibit robust current signals during the riboflavin redox reaction. Riboflavin displays a distinct oxidation peak at -0.136V (vs. Ag/AgCl, 3.0M KCl) in a Britton-Robinson buffer solution (BRBS) at pH 2, which was employed for quantification. The electrode demonstrates a broad linear range from 0.05 to 10µM, boasting a detection limit of 0.03µM. Repeatability stands at 1.45%, while reproducibility is 6.61%. Testing the influence of common interfering compounds yielded negligible results. The sensor effectively determines riboflavin content in pharmaceutical formulations without any prior treatment. This method presents an economical, modifier-free sensor with exceptional sensitivity and cost-effectiveness, making it suitable for rapid riboflavin quantification.

Monitoring the oxidative function of hydroxytyrosol and potential interactions with glutathione produced by human cells

Hydroxytyrosol (HT) has outstanding antioxidant properties, however, the lack of information regarding its potential interactions with biological systems prevents the direct application of HT in the field of medicine. In particular, the interaction of HT with antioxidant defense systems based on tripeptides containing thiols (glutathione, GSH) remains elusive and requires further investigation. This study investigated the electrochemical behavior of HT in Britton-Robinson buffer solution (B-R) with and without GSH using bulk electrolysis (BE) and cyclic voltammetry (CV). The reaction pathways of HT and oxidation products were identified by combining ultrahigh-performance liquid chromatography and mass spectrometry (UHPLC-MS). The findings of the study indicate that the phenolic ring of HT experiences a quasi-reversible oxidation process. This process is associated with the oxidation of the catechol moiety through the transfer of 2e−/2H+ in the presence of existing GSH. As a result of this oxidation, a quinone is produced. The quinone molecule can undergo reduction, leading to the regeneration of the HT molecule. Alternatively, it can undergo further modification by interacting with GSH, resulting in the formation of mono-GSH-HT, bi-GSH-HT, and bi-GSH-HT trimer conjugates. Using density functional theory (DFT), the ratio of disulfide, mono-GSH-HT, bi-GSH-HT, and bi-GSH-HT trimer formation energies (Ef) was determined to be 4.5:1.8:1.1:1.4 which are consistent with UHPLC-MS measurement. Accordingly, the formation of the disulfide form of GSH and parent HT is preferred over the formation of other conjugates. The higher values of electrophilicity index (ω) for the HT trimer and quinone suggest a remarkable ability to interact with cells in biological systems.

Development of environmentally friendly voltammetric methods for the individual and simultaneous determination of antihypertensives: Validation and application

In this study, voltammetric methods were developed and validated for the individual determination of lisinopril (LSNP) and its association with hydrochlorothiazide (HCTZ) employing a cathodically pretreated boron-doped diamond (CP-BDD) electrode. The studies of the experimental and instrumental parameters that affect the performance of both methods were carefully carried out by optimizing each parameter. The methods were validated by evaluating the figures of merits recommended by the validation guidelines. The method for the individual determination of LSNP presented a linear working range between 9.99 and 196.01 nmol L−1, with a limit of detection of 3.05 nmol L−1 by differential pulse voltammetry in BR buffer solution (pH 2.0). Simultaneous analytical curves over the concentration ranges of 0.40–3.99 and 0.050–1.045 μmol L−1 for HCTZ and LSNP, respectively, were obtained by square-wave voltammetry in Britton-Robinson buffer solution (pH 3.0). The limit of detection values calculated were 0.052 μmol L−1 and 0.020 μmol L−1, respectively for HCTZ and LSNP. The sensitivity observed for individual analytical curves of HCTZ and LSNP was statistically equal to that obtained for the simultaneous analytical curves at the 95 % confidence level. The developed methods were applied to determine these drugs in environmental, biological, and pharmaceutical samples, with satisfactory results. The method's greenness was assessed demonstrating that both validated methods constitute a greener alternative to conventional analytical methods reported in the literature.

Simultaneous Electrochemical Quantification of Favipiravir and Molnupiravir as Antiviral Drugs for the Treatment of COVID-19 by Using a Glassy Carbon Electrode Modified by Pd/Co-Mn-MOF-74

An electrochemical monitoring of Favipiravir (Favi) and Molnupiravir (Moln) as effective drugs for the treatment of COVID-19 was conducted for the first time in the presented research. A modification of the glassy carbon electrode (GCE) with Metal–organic frameworks (MOFs) was applied for the determination process by using the Square Wave Voltammetry (SWV) technique. Transmission electron microscopy (TEM), Fourier Transform Infrared (FTIR), the Energy Dispersive X-ray (EDX) and, X-ray Diffraction (XRD) techniques applied to check the characterization of synthesized Modified-MOFs. In Britton–Robinson buffer solutions (BR) with pH = 7, two well-defined peaks appeared on the Pd/Co-Mn-MOF-74/GCE for 10 μM Moln and Favi were 423 and 1143 mV while the oxidation currents were 32.6 and 18.4 μA, respectively. The detection limit for Moln and Favi were calculated based on 3 Signal/Noise as 0.002 and 0.003 μM, respectively. The ability of the Pd/Co-Mn-MOF-74/GCE was checked by monitoring the Moln and Favi in urine and blood and comparing the obtained data with HPLC data. The obtained data were in good agreement with each other which demonstrates that the presented method was one of the best analytical methods for the monitoring of Moln and Favi in the laboratory.

Synthesis and voltammetric studies of azo dye compounds derived from 3-hydroxyquinolin-2-one in aqueous media

Azo dye derived from 3-hydroxyquinolin-2-one were synthesized and characterized by IR and 1HNMR. DC-polarography and cyclic voltammetry behavior of these compounds is considered in Britton-Robinson buffer solutions in the range of pH 2–12. The investigated azo compounds gave an irreversible dc-polarographic wave owing to the reduction of azo center with the consumption of four electrons controlled by diffusion, through the splitting of the N = N center to the amine group. For nitro derivative a single 8-elctron wave is observed. In cyclic voltammetry a cathodic peak was obtained for all compounds in the entire pH range. The kinetic data of the reduction process was determined and examined in view of the influence of medium and substitutes and the reduction mechanism was found to be H+, e, e, H+. The free energy of activation ∆G* was observed to increase whereas the rate constant kf,h diminishes with rise of the pH of the electrolysis medium. The effect of substituents was studied based on Hammett constants and showed that the electron withdrawing group facilitate the electrode reaction whereas the electron donating ones hinder it.

Voltammetric Determination of 7-Ethylthio-3-Nitro-1,2,4-Triazolo[5,1-c]-1,2,4-Triazin-4-One Dihydrate Sodium Salt as a Potential Antiviral Drug

The sodium salt of 7-ethylthio-3-nitro-1,2,4-triazolo[5,1-c]-1,2,4-triazin-4-one dihydrate (1) is one of promising antiviral compounds that have shown a pronounced biological activity against influenza virus subtype H5N1, West Nile, and SARS (severe acute respiratory syndrome). Using cyclic voltammetry, it was shown that the electrochemical activity of compound 1 in a Britton–Robinson buffer solution (BRB) of pH 2.0 on a glassy carbon electrode is due to the electrochemical reduction of the nitro group conjugated with the heterocyclic system. A method was developed for the determination of compound 1 by direct cathodic square-wave voltammetry. The linearity region of the calibration curve in a BRB solution of pH 7.0 is 10–300 mg/L (R2 = 0.999), the limit of detection is 1.5 mg/L, and the limit of quantification is 4.5 mg/L. The accuracy of the developed procedure is close to 100%, the relative standard deviation is 3.6%.

Ultra-sensitive determination of serotonergic antidepressant vortioxetine in pharmaceutical and blood samples at the boron-doped diamond electrode

In this work, an ultra-sensitive voltammetric method for the determination of serotonergic antidepressant vortioxetine (VTX) was developed using an anodically pretreated boron-doped diamond electrode and square-wave voltammetry (SWV). In this modification-free platform, VTX was irreversibly oxidized at 1.09 V (vs. Ag/AgCl (3.0 mol/L KCl)) in Britton–Robinson buffer solution (pH 4.0). Under optimized instrumental parameters of SWV, the oxidation current of VTX increased linearly in the concentration range of 9.99 – 148 nmol/L, obtaining a limit of detection of 2.35 nmol/L. The method was successfully applied to commercially available Brintellix® tablets, and the results obtained were statistically similar to those obtained by a spectrophotometric method. Additionally, the simultaneous determination of VTX and amiloride was demonstrated and applied in blood rat serum. The method proved not to suffer from matrix interference providing excellent recoveries.

Simple and selective screening method for the synthetic cathinone MDPT in forensic samples using carbon nanofiber screen-printed electrodes

3′,4′-Methylenedioxy-N-tert-butylcathinone (MDPT), also known as tBuONE or D-Tertylone, is a synthetic cathinone (SC) frequently abused for recreational purposes due to its potent stimulant effects and similarity to illegal substances like methamphetamine and ecstasy. The structural diversity and rapid introduction of new SC analogs to the market poses significant challenges for law enforcement and analytical methods for preliminary screening of illicit drugs. In this work, we present, for the first time, the electrochemical detection of MDPT using screen-printed electrodes modified with carbon nanofibers (SPE-CNF). MDPT exhibited three electrochemical processes (two oxidations and one reduction) on SPE-CNF. The proposed method for MDPT detection was optimized in 0.2 mol L−1 Britton-Robinson buffer solution at pH 10.0 using differential pulse voltammetry (DPV). The SPE-CNF showed a high stability for electrochemical responses of all redox processes of MDPT using the same or different electrodes, with relative standard deviations less than 4.7% and 1.5% (N = 3) for peak currents and peak potentials, respectively. Moreover, the proposed method provided a wide linear range for MDPT determination (0.90–112 μmol L−1) with low LOD (0.26 μmol L−1). Interference studies for two common adulterants, caffeine and paracetamol, and ten other illicit drugs, including amphetamine-like compounds and different SCs, showed that the proposed sensor is highly selective for the preliminarily identification of MDPT in seized forensic samples. Therefore, SPE-CNF with DPV can be successfully applied as a fast and simple screening method for MDPT identification in forensic analysis, addressing the significant challenges posed by the structural diversity of SCs.

Synthesis of pH-Sensitive Nitrogen-Doped Carbon Dots with Biological Imaging Function and Their Application in Cu2+ and Fe2+ Determination by Ratiometric Fluorescent Probes.

pH-sensitive nitrogen-doped carbon dots (N-CDs) were synthesized using immature seeds of elm trees as a carbon source and ethylenediamine as a coreactant through a facile one-step hydrothermal method. The N-CDs were characterized using fluorescence spectroscopy, fluorescence lifetime, ultraviolet-visible absorption, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy, as well as transmission electron microscopy. The N-CDs displayed excellent fluorescence properties and responded to pH changes. The N-CDs exhibited low toxicity and good biocompatibility and had the potential to be used for the biological imaging of HeLa cells and mung bean sprouts. Utilizing the mechanism of fluorescence resonance energy transfer, ratiometric fluorescent probes were prepared by simple mixing of N-CDs and fluorexon in a Britton-Robinson buffer solution. The ratiometric fluorescent probe was used to detect Cu2+ and Fe2+. The linear equations were RCu = -0.0591[Q] + 3.505 (R2 = 0.992) and RFe = -0.0874[Q] + 3.61 (R2 = 0.999). The corresponding limits of detection were 0.5 and 0.31 μM, respectively. The good results had been obtained in the actual samples detection.

The Effect of Rare-Earth Elements on the Morphological Aspect of Borate and Electrocatalytic Sensing of Biological Compounds.

Adjusting the morphological characteristics of a material can result in improved electrocatalytic capabilities of the material itself. An example of this is the introduction of rare-earth elements into the borate structure, which gives a new perspective on the possibilities of this type of material in the field of (bio)sensing. In this paper, we present the preparation of borates including La, Nd and Dy and their application for the modification of a glassy carbon electrode, which is used for the non-enzymatic detection of a biologically relevant molecule, vitamin B6 (pyridoxine). Compared with the others, dysprosium borate has the best electrocatalytic performance, showing the highest current and the lowest impedance, respectively, as determined using cyclic voltammetry and impedance tests. Quantitative testing of B6 was performed in DPV mode in a Britton-Robinson buffer solution with a pH of 6 and an oxidation potential of about +0.8 V. The calibration graph for the evaluation of B6 has a linear range from 1 to 100 μM, with a correlation coefficient of 0.9985 and a detection limit of 0.051 μM. The DyBO3-modified electrode can be used repeatedly, retaining more than 90% of the initial signal level after six cycles. The satisfactory selectivity offered a potential practical application of the chosen method for the monitoring of pyridoxine in artificially prepared biological fluids with acceptable recovery. In light of all the obtained results, this paper shows an important approach for the successful design of electrocatalysts with tuned architecture and opens new strategies for the development of materials for the needs of electrochemical (bio)sensing.

Ultrasensitive and highly selective electrochemical determination of mesalazine in pharmaceutical, biological and environmental samples with the use of Co-Mordenite/Mesoporous Carbon modified Glassy Carbon Electrode

In this paper, an ultrasensitive and highly selective analytical method for the voltammetric determination of the anti-inflammatory drug mesalazine (MES) at the Co-exchanged mordenite/mesoporous carbon modified glassy carbon electrode (Co-MOR/MC-GCE) is presented. The combination of unique properties of zeolite and mesoporous carbon, affirmed by conducting morphology and textural parameters studies, resulted in the fabrication of the unique platform sensing, which exhibited a significant enhancement effect of MES oxidation peak current. In the voltammetric determination of mesalazine by the means of differential pulse voltammetry (DPV), univariate optimization stage of the instrumental parameters and the pH value of the supporting electrolyte was performed. In 0.04 mol L−1 Britton-Robinson buffer solution (pH 2.0), the oxidation peak of MES at 0.41 V vs. Ag | AgCl | 3 M KCl reference electrode revealed a linear response in the range of 0.99 – 99.01 µg L−1 (6.47·10−9 – 6.47·10−7 mol L−1) with the limit of detection (LOD) equal to 0.27 µg L−1 (1.76·10−9 mol L−1). The developed protocol was successfully applied for the direct determination of mesalazine in pharmaceuticals, environmental waters, and biological fluids (human urine and serum) with recovery of 103.4 – 119.3%.

Valence-Engineered Oxidase-Mimicking Nanozyme with Specificity for Aromatic Amine Oxidation and Identification.

Oxidase-mimicking nanozymes with specificity for catalyzing oxidation of aromatic amines are of great significance for recognition of aromatic amines but rarely reported. Herein, Cu-A nanozyme (synthesized with Cu2+ as a node and adenine as a linker) could specifically catalyze oxidation of o-phenylenediamine (OPD) in Britton-Robinson buffer solution. Such a specific catalytic performance was also corroborated with other aromatic amines, such as p-phenylenediamine (PPD), 1,5-naphthalene diamine (1,5-NDA), 1,8-naphthalene diamine (1,8-NDA), and 2-aminoanthracene (2-AA). Moreover, the presence of salts (1 mM NaNO2, NaHCO3, NH4Cl, KCl, NaCl, NaBr, and NaI) greatly mediated the catalytic activity with the order of NaNO2 < blank ≈ NaHCO3 < NH4Cl ≈ KCl ≈ NaCl < NaBr < NaI, which was due to anions sequentially increasing interfacial Cu+ content via anionic redox reaction, while the effect of cations was negligible. With the increased Cu+ content, Km decreased and Vmax increased, indicating valence-engineered catalytic activity. Based on high specificity and satisfactory activity, a colorimetric sensor array with NaCl, NaBr, and NaI as sensing channels was constructed to identify five representative aromatic amines (OPD, PPD, 1,5-NDA, 1,8-NDA, and 2-AA) as low as 50 μM, quantitatively analyze single aromatic amine (with OPD and PPD as model analysts), and even identify 20 unknown samples with an accuracy of 100%. In addition, the performance was further validated through accurately recognizing various concentration ratios of binary, ternary, quaternary, and quinary mixtures. Finally, the practical applications were demonstrated by successfully discriminating five aromatic amines in tap, river, sewage, and sea water, providing a simple and feasible assay for large-scale scanning aromatic amine levels in environmental water samples.

The influence of bismuth participation on the morphological and electrochemical characteristics of gallium oxide for the detection of adrenaline.

In this work, we investigated the morphological and electrochemical properties of gallium/bismuth mixed oxide. The bismuth concentration was varied from 0 to 100%. The correct ratio was determined with inductively coupled plasma-optical emission spectroscopy (ICP-OES), while surface characteristics were determined using scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurement. Electrochemical characteristics were studied using electrochemical impedance spectroscopy (EIS) in the Fe2+/3+ couple. The obtained materials were tested for adrenaline detection. After square wave voltammetry (SWV) optimization, the best electrode showed a wide linear working range from 7 to 100µM at pH 6 of the Britton-Robinson buffer solution (BRBS) supporting electrolyte. The limit of detection (LOD) for the proposed method was calculated as 1.9µM, with a limit of quantification (LOQ) of 5.8µM. The excellent selectivity of the proposed method, with good repeatability and reproducibility, strongly suggests the possible application of the procedure for the determination of adrenaline in artificially prepared real samples. The practical applicability with good recovery values indicates that the morphology of the materials is closely connected with other parameters, which further suggests that the developed approach can offer a low-cost, rapid, selective, and sensitive method for adrenaline monitoring.

Development of stripping voltammetry using glassy carbon electrode modified with electrochemical reduced graphene oxide for the determination of amaranth in soft drink and candy samples

In this study, the manufacturing conditions of glassy carbon electrode modified with electrochemical reduced graphene oxide (ErGO/GCE) were elucidated to determine amaranth in soft drink and candy samples by adsorptive stripping voltammatry. The ErGO/GCE was fabricated through an electrochemical reduction process of graphene oxide in the potential range from 0 V to −1.5 V using cyclic voltammetry method. Characteristics of graphene oxide and reduced graphene oxide were studied by FT-IR, XRD, TEM, SEM. Amaranth is adsorbed on the ErGO/GCE working electrode surface through an irreversible oxidation process. The optimal conditions used to determine amaranth are Britton-Robinson buffer solution of pH 3.0, an adsorption potential at 0 V, an adsorption time of 30 s, at a scan rate of 20 mV/s, a linearity range from 1.0 × 10−7 mol. L−1 to 1.0 × 10−6 mol. L−1, a (LOD) detection limit of 2.8 × 10−8 mol. L−1 and a (LOQ) qualification limit of 9.3 × 10−8 mol. L−1. The proposed method can be applied to determine amaranth dye in food.

Determination of Coumarin in Mikania glomerata Infusions by Square-Wave Voltammetry Using a Boron-Doped Diamond Electrode

Infusions of Mikania glomerata Sprengel (guaco) leaves are used in Brazil for the treatment of respiratory diseases. Coumarin is the chemical marker of guaco for quality control purposes. This work proposes a voltammetric methodology to determine coumarin by using a borondoped diamond electrode. At pH 10 (0.1 mol L-1 Britton-Robinson buffer solution), coumarin is irreversibly oxidized around +1.77 V in a process predominantly controlled by diffusion. The methodology described here presented a linear range from 1.54 to 15.3 μg mL-1 with limits of detection and quantification of 0.20 and 0.62 μg mL-1, respectively. Analysis of variance confirmed the significance of the regression and the absence of lack-of-fit at the confidence level of 95%. Infusion of commercial guaco leaves was directly analyzed, and results were in agreement with high-performance liquid chromatography after applying the paired t-test at a confidence level of 95%.

Voltammetric determination of Molnupiravir used in treatment of the COVID-19 at magnetite nanoparticle modified carbon paste electrode

To reduce the progression of the viral process in patients infected with COVID-19, new treatments and drug active substances are needed. One of these drugs is Molnupiravir (MNP) which has a direct antiviral effect and has also proven to be highly effective in reducing the azopharyngeal SARS-CoV-2 infectious virus and viral RNA. Due to the importance and frequent use of this drug in the treatment of COVID-19, its accurate, quick, and cheap detection in pharmaceutical or biological samples is crucial. In this work, electrochemical behavior and sensitive voltammetric determination of MNP are described using a magnetite nanoparticle modified carbon paste electrode (Fe3O4@CPE) for the first time. Fe3O4 nanoparticles (NPs) were characterized by recording their transmission electron microscopy (TEM) images, energy dispersive X-ray (EDX), and X-ray diffraction (XRD) spectra. Cyclic voltammetric measurements showed that MNP was irreversibly oxidized at Fe3O4@CPE at 760 mV in pH 2.0 Britton Robinson buffer solution (BRBS). The peak current of MNP was increased approximately threefold at Fe3O4@CPE compared to bare CPE due to a good electrocatalytic efficiency of Fe3O4 NPs. According to differential pulse voltammetric studies, the fabricated electrode exhibited a linear range (LR) between 0.25 and 750 µM with sensitivity and limit of detection (LOD) of 4591.0 µA mM−1 cm−2 and 0.05 µM, respectively. On the other hand, although lower sensitivity (327.3 µA mM−1 cm−2) was obtained from CV compared to DPV, a wider linear calibration curve between 0.25 and 1500 µM was obtained in CV. Studies performed in tablet samples confirmed that the Fe3O4@CPE exhibits high applicability for selective and accurate voltammetric determination of MNP in real samples.

Electrochemical Determination of Morphine in Urine Samples by Tailoring FeWO4/CPE Sensor.

Morphine (MORPH) is natural alkaloid and mainly used as a pain reliever. Its monitoring in human body fluids is crucial for modern medicine. In this paper, we have developed an electrochemical sensor for submicromolar detection of MORPH. The sensor is based on modified carbon paste electrode (CPE) by investigating the FexW1-xO4 ratio in iron tungstate (FeWO4), as well as the ratio of this material in CPE. For the first time, the effect of the iron-tungsten ratio in terms of achieving the best possible electrochemical characteristics for the detection of an important molecule for humans was examined. Morphological and electrochemical characteristics of materials were studied. The best results were obtained using Fe1W3 and 7.5% of modifier in CPE. For MORPH detection, square wave voltammetry (SWV) was optimized. Under the optimized conditions, Fe1W3@CPE resulted in limit of detection (LOD) of the method of 0.58 µM and limit of quantification (LOQ) of 1.94 µM. The linear operating range between 5 and 85 µM of MORPH in the Britton-Robinson buffer solution (BRBS) at pH 8 as supporting electrolyte was obtained. The Fe1W3@CPE sensor resulted in good selectivity and excellent repeatability with relative standard deviation (RSD) and was applied in real-world samples of human urine. Application for direct MORPH detection, without tedious sample pretreatment procedures, suggests that developed electrochemical sensor has appeared to be a suitable competitor for efficient, precise, and accurate monitoring of the MORPH in biological fluids.

Development of modified pyrophyllite carbon paste electrode for carbendazim detection

ABSTRACT This study aims to design the pyrophyllite-adapted carbon paste electrode (pCPE) and test it for potential use in wastewater purification systems. Structural characterization of pure pyrophyllite ore and mechanically modified pyrophyllite in mortar and pestle has been followed by XRD, SEM, PSA, and FTIR. Electrochemical characteristics were studied by cyclic voltammetry of pyrophyllite CPE in sulfuric acid and potassium ferrocyanide, as redox model compounds. Delamination, gliding, and folding of the layers and a decrease in particle and crystallite size have been observed, leading to the excellent electrocatalytic activity of pCPE. The developed pCPE has numerous benefits such as a simple preparation method, rapid response, and good sensitivity. The oxidation peak of carbendazim appears in Britton-Robinson buffer solutions (pH 4) at +0.9 V vs. Ag/AgCl. The developed method is linear in the concentration range of 3.2–29.2 ng cm−3, with r = 0.999 and the limit of detection of 1.9 ng cm−3.