mA Mol Research Articles

Efficient recycling of Co3O4 from spent lithium-ion batteries and its application as an electrochemical sensor and photocatalyst

Green recycling of spent lithium-ion batteries (LIBs) is a fundamental step toward environmental preservation and increased recovery of raw materials. In this study, lactic acid was used to leach the cathode active material of LIBs. The recycled material (Co3O4) was obtained by selective precipitation of the leachate with KOH, followed by calcination for 4.5 h at 450 °C. The composition and microstructure of the recycled material were confirmed by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy. Co3O4 was applied as a non-enzymatic electrochemical sensor for determination of ascorbic acid and as a photocatalyst in the degradation of methylene blue. The electrochemical sensor consisted of a printed electrode of carbon nanotubes modified with an 85:10:5 (w/w/w) mixture of recycled material, carbon black, and polyvinylidene fluoride (PVDF), respectively. Linear sweep voltammetry was used to measure the oxidation of ascorbic acid at 0.10 V. The analytical curve of the sensor had a coefficient of determination of 0.9915, sensitivity of 0.0498 ± 0.0023 μA mol L−1, and detection limit of 0.0245 mol L−1 in the concentration range of 0.166 to 1.0 mmol L−1. Co3O4 applied as a photocatalyst reached an efficiency of 61.47% in the decolorization of methylene blue after 120 min of reaction in the presence of H2O2 and UV light. Co3O4 recycled from spent LIBs is a promising source of raw materials for the development of non-enzymatic electrochemical sensors and photocatalysts via a sustainable and environmentally friendly route.

Electrochemical Sensor Based on a Composite of Reduced Graphene Oxide and Molecularly Imprinted Copolymer of Polyaniline-Poly(o-phenylenediamine) for Ciprofloxacin Determination: Fabrication, Characterization, and Performance Evaluation.

Contamination of antibiotics in water is a major cause of antibiotic resistance (ABR) in pathogens that endangers human health and food security worldwide. Ciprofloxacin (CIP) is a synthetic fluoroquinolone (FQ) antibiotic and is reportedly present in surface water at a concentration exceeding the ecotoxicological predicted no-effect concentration in some areas. This study fabricated a CIP sensor using an electropolymerized molecularly imprinted polymer (MIP) of polyaniline (PANI) and poly(o-phenylenediamine) (o-PDA) with CIP recognition sites. The MIP was coated on a reduced graphene oxide (rGO)-modified glassy carbon electrode (rGO/GCE) and operated under a differential pulse voltammetry (DPV) mode for CIP detection. The sensor exhibited an excellent response from 1.0 × 10-9 to 5.0 × 10-7 mol L-1 CIP, showing a sensor detection limit and sensitivity of 5.28 × 10-11 mol L-1 and 5.78 μA mol-1 L, respectively. The sensor's sensitivity for CIP was 1.5 times higher than that of the other tested antibiotics, including enrofloxacin (ENR), ofloxacin (OFX), sulfamethoxazole (SMZ), and piperacillin sodium salt (PIP). The reproducibility and reusability of the sensor devices were also studied.

Electrochemical Detection of H2O2 Using an Activated Glassy Carbon Electrode

Hydrogen peroxide (H2O2) is extensively used for sterilization purposes in the food industries and pharmaceuticals as an antimicrobial agent. According to the Food and Agriculture Organization (FAO), the permissible level of H2O2 in milk is in the range of 0.04 to 0.05% w/v, so it has been prohibited to use as a preservative agent. Herein, we reported the electrochemical sensing of H2O2 in milk samples using an activated glassy carbon electrode (AGCE). For this purpose, activation of GCE was carried out in 0.1 M H2SO4 by continuous potential sweeping between −0.7 to 1.8 V for 25 cycles. The AGCE showed a redox peak at -0.18 V in the neutral medium corresponding to the quinone functional groups present on the electrode surface. AGCE was studied in (pH 7.4) 0.1 M PBS for the electro-catalysis of H2O2. The surface of the activated electrode was analysed by Raman spectroscopy and contact angle measurements. In addition, for the activated surface, the contact angle was found to be 85° which indicated the hydrophilic nature of the surface. The different optimization parameters such as (1) effect of electrolyte ions, (2) electrooxidation cycles, and (3) oxidation potential windows were studied to improve the activation process. Finally, AGCE was used to detect H2O2 from 0.1 to 10 mM and the limit of detection (LOD) was found to be 0.053 mM with a linear correlation coefficient (R2) of 0.9633. The selectivity of the sensor towards H2O2 was carried out in the presence of other interferents. The sensitivity of the AGCE sensor was calculated as 17.16 μA mol cm−2. Finally, the commercial application of the sensor was verified by testing it in milk samples with H2O2 in the recovery range of 95%–98%.

Biobased PET from lignin using an engineered cis, cis-muconate-producing Pseudomonas putida strain with superior robustness, energy and redox properties

Polyethylene terephthalate (PET), the most common synthetic polyester today, is largely produced from fossil resources, contributing to global warming. Consequently, sustainable sources must be developed to meet the increasing demand for this useful polymer. Here, we demonstrate a cascaded value chain that provides green PET from lignin, the world's most underutilized renewable, via fermentative production of cis, cis-muconate (MA) from lignin-based aromatics as a central step. Catechol, industrially the most relevant but apparently also a highly toxic lignin-related aromatic, strongly inhibited MA-producing Pseudomonas putida MA-1. Assessed by 13C metabolic flux analysis, the microbe substantially redirected its carbon core fluxes, resulting in enhanced NADPH supply for stress defense but causing additional ATP costs. The reconstruction of MA production in a genome-reduced P. putida chassis yielded novel producers with superior pathway fluxes and enhanced robustness to catechol and a wide range of other aromatics. Using the advanced producer P. putida MA-10 catechol, MA could be produced in a fed-batch process from catechol (plus glucose as additional growth substrate) up to an attractive titer of 74 g L−1 and a space-time-yield of 1.4 g L−1 h−1. In terms of co-consumed sugar, the further streamlined strain MA-11 achieved the highest yield of 1.4 mol MA (mol glucose)−1, providing a striking economic advantage. Following fermentative production, bio-based MA was purified and used to chemically synthetize the PET monomer terephthalic acid and the comonomer diethylene glycol terephthalic acid through five steps, which finally enabled the first green PET from lignin.

Correction to "β 2-Adrenoceptor Agonists Promote Extracellular Signal-Regulated Kinase 1/2 Dephosphorylation in Human Airway Epithelial Cells by Canonical, cAMP-Driven Signaling Independently of β-Arrestin 2".

In the above article, [Hamed O, Joshi R, Michi AN, Kooi C, and Giembycz MA (2021) Mol Pharmacol , 100( 4 ) [388-405][1]; DOI: <https://doi.org/10.1124/molpharm.121.000294>], an equation was omitted from the Materials and Methods section due to a compositor error. The equation is provided below. ![

Development and characterization of enzymatic biosensor based on lipase from porcine pancreas for propylparaben detection

PurposeThe purpose of this paper is to study the immobilization of porcine pancreatic lipase (PPL), in an organic matrix by a covalent cross-linking method to sense propylparaben (PP) present in aqueous solution.Design/methodology/approachPPL immobilization was performed by the covalent cross-linking method, using bovine serum albumin (BSA) in the presence of saturated glutaraldehyde vapor (GA). The preparation of the enzymatic membrane involves the incorporation of porcine pancreatic lipase (PPL), bovine serum albumin (BSA) and glycerol into a phosphate buffer solution (PBS). Characterization of this sensor was performed by impedance spectroscopy (EIS) and scanning electron microscope (SEM). The effect of experimental conditions such as PPL activity, potential, scan rate, PP concentration, pH and presence of interfering elements were studied by cyclic voltammetry.FindingsUnder the optimal experimental conditions, a number of significant factors were optimized. The method exhibited good linearity in the range of 10–14to 10–9 mol/L with a good correlation coefficient of 0.957, detection limit (LOD) of 3.66 × 10–15 mol/L and high sensitivity of 1.086 mA mol−1L. The authors also obtained a very good coverage rate of the surface equal to 91.44%, and hydrolytic activity of lipase is evaluated to 26.64 mmol min−1. The stability and the interference were also evaluated. The equivalent circuit used to explain the electrochemical behavior of modified electrode is a Randle circuit.Practical implicationsThe main application of biosensors is the detection of biomolecules that are either indicators of a disease. For example, electrochemical biosensing techniques can be used as clinical tools to detect breast tumors, because these compounds (PP) were found in breast tumors.Originality/valueThe result registered in this paper indicates that the developed sensor is an efficient, fast, simple and inexpensive analytical tool that can be used for the analysis of water containing PP.

A glucose biosensor based on glucose oxidase fused to a carbohydrate binding module family 2 tag that specifically binds to the cellulose-modified electrode

The method of immobilization of glucose oxidase (GOD) on electrodes is especially important for the fabrication and performance of glucose biosensors. In this study, a carbohydrate binding module family 2 (CBM2) was successfully fused to the C terminal of GOD with a natural linker (NL) in endo-β-xylanase by genetic recombination, and a fusion GOD (GOD-NL-CBM2) was obtained. The CBM2 was used as an affinity adsorption tag for immobilization of the GOD-NL-CBM2 on a cellulose modified electrode. The specific activity of GOD-NL-CBM2 was comparable to that of the wild type GOD. In addition, the CBM2 tag of fusion GOD almost maintained its highest binding capacity under optimal catalytic conditions (pH 5.0, 50 °C). The morphology and composition analysis of the cellulose film reacted with and without GOD or GOD-NL-CBM2 confirmed the immobilization of GOD-NL-CBM2. The electrochemical properties of the GOD-NL-CBM2/cellulose film bioelectrode, with a characteristic peak of H2O2 at +0.6 V in the presence of glucose, revealed the capability of the immobilized GOD-NL-CBM2 to efficiently catalyze glucose and produce H2O2. Additionally, the current signal response of the biosensor to glucose was linear in the concentration range from 1.25 to 40 mM (r2 ≥ 0.99). The sensitivity and detection limit of the GOD-NL-CBM2/cellulose film bioelectrode were 466.7 μA mol−1 L cm-2 and 0.475 mM (S/N = 3), respectively. Moreover, the glucose biosensor exhibited a rapid current change (< 5 s), high reproducibility (Relative standard deviation, RSD < 5%), substrate selectivity and stability, and retained about 80 % of the original current response after 2 months. The affinity adsorption-based immobilization strategy for GOD provides a promising approach to develop a high performance glucose biosensor.

Development of new modified electrode based on β-cyclodextrin for methylene blue detection

PurposeThis paper aims to focus on the development and characterization of a new electrochemical sensor, designed for the detection of methylene blue present in aqueous medium.Design/methodology/approachThis sensor is obtained through the coupling of a polymeric membrane and an ion-sensitive electrode (platinum electrode). The preparation of the polymeric membrane involves the incorporation of a receptor: β-cyclodextrin (β-CD), a polymer (polyvinylchloride) and a plasticizer (dioctylphtalate). Cyclic voltammetry method (CV) was used to investigate the electrical properties of this electrochemical sensor. The effect of the experimental parameters such as dye initial concentration, scan rate, interfering elements presence and additional Nafion membrane presence was investigated in this paper.FindingsThe results are interesting because the developed sensor gives a linear response in concentrations range of 10−13 M–10−3 M with a good correlation coefficient of 0.979 and a detection limit of 10−13 M, which reflects the sensitivity of this sensor to the target element. The sensibility value is equal to 2. 40 µA mol−1 L.Originality/valueThe present study has shown that the modified electrode is a very good candidate in terms of price, sensibility and reproducibility for the construction of the sensitive sensor for the control of wastewater containing methylene blue.

Functionals Aspects and Simultaneous Detection of Dopamine, Ascorbic Acid and Uric Acid Using Chitosan-Catechol Graphene and Carbon Nanotube Modified Electrodes

Dopamine functions as a neurotransmitter in the brain. The dysfunction of the dopaminergic system is the leading cause of numerous diseases such as Parkinson’s disease. Hence, it is important to find selective and sensitive detection methods for the early diagnosis of diseases related to the abnormal levels of dopamine. In this study, we show a new electrochemical sensing platform based on carbon nanotube (SWCNT) and a sheet of graphene (GRA). The novelty of our sensor is the coating of the substrates with chitosan-catechol (CC) by electrodeposition, enhancing the dopamine response by 70%. The dose-response for each set of electrodes (bare CNT, bare GRA, and coated CNT as well as coated GRA) was measured. Finally, the electrodes were tested in cerebrospinal fluid (artificial and human), for the detection of millimolar to nanomolar levels of dopamine. The electrodes exhibited high sensitivity (2.03mA mol·L-1, 1.45 mA mol·L-1, 0.0298 mA mol·L-1, and 0.0559 mA mol·L-1 for the modified CNT, bare CNT, modified GRA and bare GRA, respectively, for the oxidation of DA. The oxidation peak current was proportional to the concentration of DA in the range from 50×10-6 to 50x10-9 M (n= 6, r2 =0.98). The dopamine recovery in human CSF were, 49-78% and 65-65% with coated graphene and CNT electrodes, respectively. Our results indicate that the CC modified CNT electrodes achieved the best recovery, sensitivity, limit of detection, and selectivity compared to the uncoated CNT as well as the coated and uncoated graphene electrodes.

A Novel Design and Fabrication of Ascorbic Acid Sensitive Biosensor Based on Combination of HAP/rGO/AuNPs Composite and Ascorbate Oxidase

In this study, a new HAP/rGO/AuNPs-AO modified carbon electrode (GCE) was fabricated for amperometric detection of ascorbic acid. The HAP/rGO/AuNPs composite was prepared by one-step hydrothermal method. The large specific surface area, strong adsorption and excellent biocompatibility of HAP nanowires enabled fast, stable and accurate detection of ascorbic acid. As array of quantum dot, AuNPs had strong electrocatalytic activity in addition to good adsorption to enzymes, which could provide high sensitivity and low limit of detection for biosensor. Then rGO ensured that current signal could be quickly transferred from the composite to electrode. Under the optimum conditions, the prepared biosensor demonstrated a wide linear range from 0.39 to 36 mM (R2 = 0.99845), a low limit of detection (3.39 μM, S/N = 3) and a high sensitivity (15.949 mA moL−1) with good selectivity, stability (10.8%) and repeatability (3.9%), which might providing a reasonable and reliable way for ascorbic acid detection.

Preparation and Voltammetric Application of a Zr(IV) Functionalized Spongolite for the Electrocatalytic Oxidation of Hydrazine

This study demonstrates an additional exploration of the possibilities of modifying the surface of spongolite spicules, a biogenic silica, in order to prepare natural inorganic composites for application in catalytic oxidation processes. In this context, a novel hybrid material was synthesized from the inorganofunctionalization of a spongolite with zirconium(IV) (EZr). This material was then reacted with potassium hexacyanoferrate(III) and applied in a subsequent reaction with copper ions. The obtained material (EZrCuH) was characterized by scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), and cyclic voltammetry (CV). The CV of the graphite paste modified with EZrCuH exhibited two redox couples with midpoint potentials (Eθ′) equal to 0.36 and 0.74 V, attributed to the CuI/CuII and FeII(CN)6/FeIII(CN)6 processes (1.0 mol L−1, KCl pH 7.0, v = 20 mV s−1), respectively. The EZrCuH-modified graphite paste electrode presented electrocatalytic activity in the oxidation of different hydrazine concentrations and an analytical curve with a linear response of 8.0 × 10−7 to 4.0 × 10−5 mol L−1 (R2 = 0.999, relative standard deviation = ± 2% (n = 3)), and limit of detection of 8.33 × 10−7 mol L−1 and an amperometric sensitivity of 8.21 mA mol−1 L−1. Therefore, this material can be considered as a potential candidate for the manufacturing of electrochemical sensors intended for the easy and rapid detection of hydrazine substances.

HPLC−EC Analysis of Estrogenic Compounds: A Comparison of Diamond and Tetrahedral Amorphous Carbon Electrode Performance

AbstractHigh pressure liquid chromatography (HPLC) with amperometric detection was used to quantify estrogenic compounds in water samples. The main goal was to compare the detection figures of merit for boron‐doped diamond thin‐film (BDD) and nitrogen‐incorporated tetrahedral amorphous carbon (ta‐C : N) thin‐film electrodes. The target analytes were estrone, estradiol, and estriol. The BDD and ta‐C : N electrodes were investigated because of their excellent properties, which include a wide potential window, low background current, microstructural stability at high potentials, low limits of detection, weak molecular adsorption, fouling resistance and response reproducibility. ta‐C : N electrodes have not yet been investigated extensively in electroanalysis and are receiving increasing interest because they exhibit many of the excellent electrochemical properties of BDD electrodes and they can be deposited at room temperature by physical vapor deposition. The results reveal as low or lower background current and noise for the ta‐C : N electrode, as compared to the BDD electrode, and comparable or superior analytical detection figures of merit for all three emerging pollutants. The linear dynamic range for both electrodes was from 0.2 to 100 μmol L−1 for estriol, and 0.4 to 100 μmol L−1 for estradiol and estrone, and the sensitivity ranged from 9.1 to 11.2 mA mol L−1. For all three analytes, the limit of detection (S/N=3) ranged from 0.16–0.35 μmol L−1 (45‐95 ppb) for BDD and 0.20–0.34 μmol L−1 (58‐95 ppb) for ta‐C : N.

Effect of carbon black functionalization on the analytical performance of a tyrosinase biosensor based on glassy carbon electrode modified with dihexadecylphosphate film

Carbon Black (CB) has acquired a prominent position as a carbon nanomaterial for the development of electrochemical sensors and biosensors due to its low price and extraordinary electrochemical and physical properties. These properties are highly dependent on the surface chemistry and thus, the effect of functionalization has been widely studied for different applications. Meanwhile, the influence of CB functionalization over its properties for electroanalytical applications is still being poorly explored. In this study, we describe the use of chemically functionalized CB Vulcan XC 72R for the development of sensitive electrochemical biosensors. The chemical pre-treatment increased the material wettability by raising the concentration of surface oxygenated functional groups verified from elemental analysis and FTIR measurements. In addition, it was observed an enhancement of almost 100-fold on the electron transfer rate constant (k0) related to unfunctionalized CB, confirming a remarkable improvement of the electrocatalytic properties. Finally, we constructed a Tyrosinase (Tyr) biosensor based on functionalized CB and dihexadecylphosphate (DHP) for the determination of catechol in water samples. The resulting device displayed an excellent stability with a limit of detection of 8.7 × 10−8 mol L−1 and a sensitivity of 539 mA mol−1 L. Our results demonstrate that functionalized CB provides an excellent platform for biosensors development.

Dawson-type polyoxometalate nanoclusters confined in a carbon nanotube matrix as efficient redox mediators for enzymatic glucose biofuel cell anodes and glucose biosensors

Two new inorganic-organic hybrid materials based on heteropolyoxometalates (POMs): (C4H10N)6[P2Mo18O62]·4H2O (P2Mo18) and (C6H8NO)4[H2P2W18O62]·6H2O (P2W18) are reported as mediators for electron transfer between FAD-dependent glucose dehydrogenase (FAD-GDH) and a multiwalled carbon nanotube (MWCNT) matrix for glucose biofuel cell and biosensor applications. These polyoxometalates were chosen due to their promising redox behavior in a potential range for mediated electron transfer with the glucose oxidizing enzyme, FAD-GDH. P2Mo18 and P2W18 were immobilized on 1-pyrenemethylamine (PMA) functionalized MWCNT deposits. After immobilization of FAD-GDH, the P2W18-modified MWCNT electrode demonstrated mediated electron transfer and provided a catalytic current density of 0.34 mA cm−2 at 0.2 V vs SCE with an open circuit potential (OCP) of −0.08 V vs SCE. A 10-fold increase in catalytic current to 4.7 mA cm−2 at 0.2 V vs SCE and a slightly lower OCP of −0.10 V vs SCE was observed for an equivalent electrode modified with P2Mo18.The apparent superiority of P2Mo18 is related, at least in part, to its improved incorporation in the MWCNT matrix compared to P2W18. Both POM-modified bioanodes showed exceptional stabilities with 45% of their initial performances remaining after 15 days. The mediated electron transfer capacities of the POMs were also evaluated in a glucose sensor setup and showed very satisfying performances for glucose detection, including a sensitivity of 0.198 mA mol L−1 cm−2, a satisfying linear range between 1 mmol L−1 and 20 mmol L−1, and good reproducibility for the P2Mo18 electrode.

Voltammetric determination of ibuprofen using a carbon paste – multiwalled carbon nanotube composite electrode

ABSTRACTAn optimized voltammetric method is reported for the quantification of ibuprofen in aqueous solution using a carbon paste–multiwalled carbon nanotube composite as the working electrode. The electrode preparation and the experimental conditions were optimized; a sensitivity of 228.08 mA mol−1 L was obtained. The limits of detection and quantification were 9.1 µM and 25.5 µM, respectively, and the linear dynamic range extended from 2.36–242 µM. The repeatability was 5.35% expressed as the relative standard deviation. Using statistical analysis for the lower concentrations, the detection limit was reduced to 4.13 µM. The method was employed for the analysis of ibuprofen tablets.

Efficient nonenzymatic hydrogen peroxide sensor in acidic media based on Prussian blue nanoparticles-modified poly(o-phenylenediamine)/glassy carbon electrode

Abstract The Prussian blue nanoparticles (PBNPs) were prepared by a self-assembly process, on a glassy carbon (GC) electrode modified with a poly( o -phenylenediamine) (PoPD) film. The stepwise fabrication process of PBNPs-modified PoPD/GCE was characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy. The prepared PBNPs showed an average size of 70 nm and a homogeneous distribution on the surface of modified electrodes. The PBNPs/PoPD/GCE showed adequate mechanical, electrochemical stability and good sensitivity in comparison with other PB based H 2 O 2 sensors. The present modified electrode exhibited a linear response for H 2 O 2 reduction over the concentration range of 1–58.22 μmol L −1 with a detection limit of ca. 0.8 μmol L −1 (S/N = 3), and sensitivity of 3187.89 mA (mol L −1 ) −1 cm −2 using the amperometric method. This sensor was employed for the H 2 O 2 determination in real sample and also exhibited good interference resistance and selectivity.

Use of the oxidizing effect of copper (II) to determine 2,4-dinitrophenylhydrazine at glassy electrode by chronoamperometry

Abstract A glassy carbon electrode was used and challenged for the determination of 2,4-dinitrophenylhydrazine (DNPH). This probe showed a significantly enhanced electrochemical activity when it tested with copper (II). When challenged in amperometric batch mode, the response was stable and showed a linear dependence up to 1 × 10− 5 mol L− 1 of DNPH. The very high sensitivity toward copper (96.3 mA mol− 1 L cm− 2) was then used as the basis for developing an analytical method for DNPH detection since a non electroactive compound is formed in the presence of the copper. By selecting an appropriate concentration of copper, a concentration of DNPH as low 1.0 × 10− 8 mol L− 1 was detected. Satisfactory recovery was obtained when the system was tested in industrial water samples.

Improved D-glucose electro-oxidation at a binary catalyst of nickel and cobalt oxide modified glassy carbon electrode

The catalytic activity of a glassy carbon electrode was significantly improved by in situ oxidation of cobalt oxide by Ni2O3, with respect to glucose oxidation. The electrochemical oxidation of glucose on a glassy carbon electrode modified (GCE) by cobalt oxide (CoO x /GCE) or nickel oxide (NiO x /GCE) was examined by cyclic voltammetry, in aqueous alkaline solutions. These results were compared with those obtained on a cobalt oxide deposited on GCE previously covered by a film of nickel (CoO x /NiO x /GCE). It was found that the modified electrode by two oxides has a superior catalytic activity in the oxidation of glucose. This electrode has good linear behaviour in the concentration range of 10.0 µmol/L to 3.0 mmol/L for the quantitative analysis of glucose with a sensitivity of 79.7 mA mol–1 L. The electrode has a satisfactory stability and a long life under ambient conditions.

Mesoporous silica thin films for molecular sieving and electrode surface protection against biofouling

Electrode fouling is a major challenge for the long term use of sensors in real samples as it leads to the decay of the electroanalytical signal and is often caused by the formation of an inhibiting layer formed by biomolecules. We demonstrate here that ordered and vertically aligned mesoporous silica generated at the surface of an indium tin oxide electrode by electrochemically assisted self-assembly act as a molecular sieve and a protective layer for the electrode surface. They indeed prevent the adsorption of size excluded large undesired molecules (e.g. haemoglobin) while allowing the detection of small redox active molecules likely to reach the electrode surface through the film (e.g. propranolol) with almost no loss of sensitivity. At a bare electrode, the oxidation of propranolol is completely inhibited in the presence of 5 μM haemoglobin. At a modified electrode, the sensitivity for propranolol in the absence of haemoglobin is (72.8 ± 2.9) mA mol− 1 (R2 = 0.992, N = 7) and it remains similar in the presence of 5 μM haemoglobin with a value of (67.4 ± 7.2) mA mol− 1 (R2 = 0.992, N = 7).

Simultaneous Determination of Iron and Copper in Ethanol Fuel Using Nafion/Carbon Nanotubes Electrode

AbstractThis work presents the analytical method development for iron and copper determination in ethanol fuel. This method was developed using stripping voltammetry with a glassy carbon electrode modified with Nafion/Carbon‐nanotubes. With linear sweep stripping voltammetry was achieved a limit of detection of 7.1×10−7 mol L−1 for Fe3+ and 5.1×10−8 mol L−1 for Cu2+. The amperometric sensitivities were 2.0×106 µA mol−1 L for Fe3+ and 2.8×107 µA mol−1 L for Cu2+. The recovery study showed that the method has good accuracy and repeatability, with recovery of 108 and 103 % for Fe3+ and Cu2+ respectively.