An Electrochemical Sensor Based on Ni(II) Complex and Multi Wall Carbon Nano Tubes Platform for Determination of Glucose in Real Samples

In the present paper, a stable and selective non‐enzymatic sensor is reported for determination of glucose (Glc) by using a carbon paste electrode modified with multiwall carbon nanotubes and Ni(II)‐SHP complex as modifier in an alkaline solution. This modified electrode showed impressive activity for oxidation of glucose in NaOH solution. Herein, Ni(II)‐SHP acts as a suitable platform for oxidation of glucose to glucolactone on the surface of the modified electrode by decreasing the overpotential and increasing in the current of analyte. Under the optimum conditions, the rate constant and electron transfer coefficient between electrode and modifier, were calculated to be 1.04 s⁻¹ and 0.64, respectively. The anodic peak currents indicated a linear dependency with the square root of scan rate and this behavior is the characteristic of a diffusion controlled process. So, the diffusion coefficient of glucose was found to be 3.12×10⁻⁶ cm² s⁻¹ due to the used number of transferred electron of 1. The obtained results revealed two linear ranges (5 to 190.0 μM (R²=0.997), 210.0 to 700.0 μM (R²=0.999)) and the detection limit of 1.3 μM for glucose was calculated by using differential pulse voltammetry (DPV) method. Also, the designed sensor was used for determination of glucose in the blood serum and urine samples. Some other advantages of Ni(II)‐SHP/CNT/CPE sensor are remarkable reproducibility, stability and selectivity which can be related to using nanomaterial of carbon nanotubes due to enhancement of electrode surface area.     

Voltammetric behavior and determination of bismuth on sodium humate modified carbon paste electrode

The preconcentration and voltammetric behavior of Bi^III on a sodium humate modified carbon paste electrode was studied by means of cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV). The proposed measurement involves an initial nonelectrolytic preconcentration step in which Bi^III is complexed by the surface modifier in a solution of 0.05 M KNO₃-0.0106 M HNO₃ (pH 2.0) and a subsequent electrochemical scan step in which the preconcentrated Bi^III was reduced and then oxidized promptly in supporting electrolyte of 0.5 M HNO₃. The resulting DPSV anodic current was proportional to the concentration of Bi^III ion over the range of 4.78 × 10⁻⁸–1.44 × 10⁻⁵ M. The detection limit was 4.78 × 10⁻⁸ M. The proposed method was used to determine bismuth in various samples. Various factors affecting the electrode behavior were also investigated at the same time.     

An Ionic Liquid Bulk-Modified Carbon Paste Electrode and Its Electrocatalytic Activity toward p-Aminophenol

An ionic liquid bulk-modified carbon paste electrode （M-CPE） has been fabricated by using 1-heptyl-3-methylimidazolium bromide as a modifier. Cyclic voltammetry （CV） and differential pulse voltammetry （DPV） were used to evaluate the electrocatalytic activity of the proposed electrode by choosing p-aminophenol （p-AP） as a model compound. Both at a bare carbon paste electrode （CPE） and the M-CPE, p-AP yielded a pair of redox peaks in 0.1 mol·L^-1 phosphate buffer solution （PBS, pH 7.0）. At the CPE, the peak-to-peak potential separation （AEp） was 0.233 V, while at the M-CPE the AEp was decreased to 0.105 V. Furthermore, the current response to p-AP at the M-CPE was 10.2 times of that at the CPE by DPV. The electron transfer rate constant （ks） ofp-AP at the M-CPE was 13.3 times of that at the CPE. Under the optimal condition, a linear dependence of the catalytic current versus p-AP concentration was obtained in the range of 2.0× 10^- 6 to 3.0× 10^- 4 mol·L^-1 with a detection limit of 6.0× 10^-7 mol·L^-1 by DPV. In addition, compared to other modified method the proposed electrode exhibited distinct advantages of simple prapartion, surface renewal, good reproducibility and good stability. It has been used to determine p-AP in simulated wastewater samples.     

Enhanced Electrocatalytic Reduction of Oxadiargyl and Its Determination on 2‐(4‐((4‐Acetylphenyl)diazenyl)phenylamino)‐ethanol Modified Graphene‐Paste Electrode

The electrochemical behavior of oxadiargyl at a graphene‐paste electrode modified with an azo dye, 2‐(4‐((4‐acetylphenyl)diazenyl)phenylamino)ethanol (ADPE), ADPE/MGRPE was investigated. The modified electrode showed high electrocatalytic activity toward oxadiargyl. The apparent electron transfer rate constant (k_s) and charge transfer coefficient (α) between electrode and ADPE were 1.16 s^?1 and 0.41, respectively. The differential pulse voltammetry response of the modified graphene‐paste electrode was linear against the concentration of oxadiargyl in the range from 0.03 to 1.4 mg L^?1. The limit of detection was found to be 1.3 µg L^?1 (S/N=3). The practical analytical utility of this electrode was demonstrated by measurement of oxadiargyl in river water, soil and rice samples.     

Application of NiMoO4 Nanorods for the Direct Electrochemistry and Electrocatalysis of Hemoglobin with Carbon Ionic Liquid Electrode

In this paper NiMoO₄ nanorods were synthesized and used to accelerate the direct electron transfer of hemoglobin (Hb). By using an ionic liquid (IL) 1‐butylpyridinium hexafluorophosphate (BPPF₆) modified carbon paste electrode (CILE) as the basic electrode, NiMoO₄ nanorods and Hb composite biomaterial was further cast on the surface of CILE and fixed by chitosan (CTS) to establish a modified electrode denoted as CTS/NiMoO₄‐Hb/CILE. UV‐vis and FT‐IR spectroscopic results showed that Hb in the film retained its native structures without any conformational changes. Electrochemical behaviors of Hb entrapped in the film were carefully investigated by cyclic voltammetry with a pair of well‐defined and quasi‐reversible redox voltammetric peaks appearing in phosphate buffer solution (PBS, pH 3.0), which was attributed to the direct electrochemistry of the electroactive center of Hb heme Fe(III)/Fe(II). The results were ascribed to the specific characteristic of NiMoO₄ nanorods, which accelerated the direct electron transfer rate of Hb with the underlying CILE. The electrochemical parameters of Hb in the composite film were further carefully calculated with the results of the electron transfer number (n) as 1.08, the charge transfer coefficient (α) as 0.39 and the electron‐transfer rate constant (k_s) as 0.82 s^?1. The Hb modified electrode showed good electrocatalytic ability toward the reduction of trichloroacetic acid (TCA) in the concentration range from 0.2 to 26.0 mmol/L with a detection limit of 0.072 mmol/L (3σ), and H₂O₂ in the concentration range from 0.1 to 426.0 µmol/L with a detection limit of 3.16×10^?8 mol/L (3σ).     

Application of a Nanosensor Based on MWCNT‐Sodium Dodecyl Sulphate Modified Electrode for the Analysis of a Novel Drug,Alpha‐Hydrazinonitroalkene in Human Blood Serum

The sensitivity enhancing properties of sodium dodecyl sulphate (SDS) and multi‐walled carbon nanotubes (MWCNTs) were associated to construct a nanosensor based on carbon paste electrode (CPE) by adopting drop cast method. The drop cast method makes use of minimum modifier and the entire modified surface of the sensor is available for the analyte. Surface characterization of the electrodes was carried out using FE‐SEM and EDX. EIS was used for the electrochemical characterization. We report for the first time the electrochemical analysis based on the oxidation of the ‐OH group of a novel drug, alpha‐hydrazinonitroalkene ( I ) which was found to have antibacterial and antimicrobial properties. The electron transfer kinetic parameters such as the charge transfer coefficient α and heterogeneous rate constant k′ were calculated and they have been found to be 0.64 and 9.62 × 10⁻² cm s⁻¹ respectively. The linear response ranges for ( I ) obtained at this sensor are 1.0 × 10⁻⁷ M − 7.0 × 10⁻⁷ M and 1.0 × 10⁻⁶ M – 4.5 × 10⁻⁵ M with a detection limit of (7.03 ± 0.41) × 10⁻⁸ M (S/N=3). The interference study suggested that the sensor was free from 1000‐fold excess of UA in the determination of ( I ). It was important to note that the sensor completely eliminated Ascorbic acid (AA) signal which offered a significant analytical advantage for the determination of the drug at this sensor. The practical usefulness of the modified sensor was demonstrated by the analysis of ( I ) in blood serum.     

An Electrochemical Sensor for Determination of Ultratrace Cd,Cu and Hg in Water Samples by Modified Carbon Paste Electrode Base on a New Schiff Base Ligand

This paper describes the preparation and electrochemical application of a new chemically modified electrode for simple and highly sensitive simultaneous determination of copper, mercury and cadmium using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Firstly, a new bis‐Schiff base ligand, 2,2′‐((pyridine‐2,6‐diylbis (azanylylidene)) bis (methanylylidene))bis(4‐bromophenol) (ligand L ) has been synthesized by reaction of the 2,6‐diamino pyridine with 5‐bromo salicylaldehyde or salicylaldehyde at ethanol under refluxing. The structure of the synthesized compound resulted from the IR, ¹HNMR, MS, UV spectroscopy and elemental analysis data. Afterwards, a novel, simple and effective chemically modified carbon paste electrode with ligand L was prepared. The electrochemical properties and applications of the modified electrode, including the pH, percentage of modifier, the electron transfer, optimized conditions, linear response and detection limit were investigated. High sensitivity and reproducibility, together with the ease of preparation and regeneration of the electrode surface by simple polishing, make the electrode very suitable for the voltammetric determination of copper, mercury and cadmium in several Merck samples and water samples.     

Application of Novel Zn‐Ferrite Modified Glassy Carbon Paste Electrode as a Sensor for Determination of Cd(II) in Waste Water

This paper describes the preparation of a new sensor based on Zn‐ferrite modified glassy carbon paste electrode and its electrochemical application for the determination of trace Cd(II) ions in waste waters using differential pulse anodic stripping voltammetry (DPASV). Different Zn/Ni ferrite nanoparticles were synthesized and characterized using scanning electron microscopy (SEM) and X‐ray powder diffraction (XRPD). The prepared ferrite nanoparticles were used for the preparation of Zn‐ferrite‐modified glassy carbon paste electrode (ZnMGCPE) for determination of Cd(II) at nanomolar levels in waste water at pH 5. The different parameters such as conditions of preparation, Zn²⁺/Ni²⁺/Fe²⁺ ratio and electrochemical parameters, percentage of modifier, accumulation time, pH and accumulation potential were investigated. Besides, interference measurements were also evaluated under optimized parameters. The best voltammetric response was observed for ZnFe₂O₄ modifier, when the percentage of modifier was 3 %, accumulation time 9 min, pH of supporting electrolyte 5 and accumulation potential ?1.05 V. Thus prepared electrode displays excellent response to Cd(II) with a detection limit of 0.38 ppb, and selective detection toward Cd(II) was achieved.     

Application of Titanium Dioxide Nanowires for the Direct Electrochemistry of Hemoglobin and Electrocatalysis

Titanium dioxide (TiO₂) nanowires were synthesized and used for the realization of direct electrochemistry of hemoglobin (Hb) with carbon ionic liquid electrode (CILE) as the substrate electrode. TiO₂‐Hb composite was casted on the surface of CILE with a chitosan film and spectroscopic results confirmed that Hb retained its native structure in the composite. Direct electron transfer of Hb on the modified electrode was realized with a pair of quasi‐reversible redox waves appeared, indicating that the presence of TiO₂ nanowires could accelerate the electron transfer rate between the electroactive center of Hb and the substrate electrode. Electrochemical behaviors of Hb on the modified electrode were carefully investigated with the values of the electron transfer coefficient (α), the electron transfer number and the heterogeneous electron transfer rate constant (k_s) as 0.58, 0.98 and 1.62 s^‐1. The Hb modified electrode showed excellent electrocatalytic activity to the reduction of trichloroacetic acid and NaNO₂ with wider linear range and lower detection limit, indicating the successful fabrication of a new third‐generation biosensor.     

Electrochemical Oxidative Detection of Guanosine‐5′‐triphosphate Based on a New Ionic Liquid Modified Carbon Paste Electrode

An ionic liquid (IL) 1‐(3‐chloro‐2‐hydroxy‐propyl)‐3‐methylimidazolium trifluoroacetate was used as the modifier for the preparation of the modified carbon paste electrode (CPE). The IL‐CPE showed excellent electrocatalytic activity towards the oxidation of guanosine‐5′‐triphosphate (5′‐GTP) in a pH 5.0 Britton‐Robinson buffer solution. Due to the presence of high conductive IL on the electrode surface, the electrooxidation of 5′‐GTP was greatly promoted with a single well‐defined irreversible oxidation peak appeared. The electrode reaction was an adsorption‐controlled process and the electrochemical parameters of 5′‐GTP on IL‐CPE were calculated with the electron transfer coefficient (α) as 0.44, the electron transfer number (n) as 1.99, the apparent heterogeneous electron transfer rate constant (k_s) as 2.21 × 10^?9 s^?1 and the surface coverage (Γ_T) as 1.53 × 10^?10 mol cm^?2. Under the selected conditions a linear calibration curve between the oxidation peak currents and 5′‐GTP concentration was obtained in the range from 2.0 to 1000.0 μmol L^?1 with the detection limit as 0.049 μmol L^?1 (3σ) by differential pulse voltammetry. The proposed method showed good selectivity to the 5‘‐GTP detection without the interferences of coexisting substances and the practical application was checked by measurements of the artificial samples.     

Sensitive voltammetric determination of rutin at an ionic liquid modified carbon paste electrode

An ionic liquid modified carbon paste electrode (IL/CPE) had been fabricated by using hydrophilic ionic liquid 1-amyl-3-methylimidazolium bromide ([AMIM]Br) as a modifier. The IL/CPE was characterized by scanning electron microscope and voltammetry. Electrochemical behavior of rutin at the IL/CPE had been investigated in pH 3.29 Britton-Robinson (B-R) buffer solution by cyclic voltammetry (CV) and square wave voltammetry (SWV). The experimental results suggested that the modified electrode exhibited an electrocatalytic activity toward the redox of rutin. The electron transfer coefficient (α) and the standard rate constant (k_s) of rutin at the modified electrode were calculated. Under the selected conditions, the reduction peak current was linearly dependent on the concentration of rutin in the range of 4.0 × 10⁻⁸ to 1.0 × 10⁻⁵ mol L⁻¹ (r = 0.9998), with a detection limit of 1.0 × 10⁻⁸ mol L⁻¹ (S/N = 3). The relative standard deviation (R.S.D.) for six times successful determination of 8.0 × 10⁻⁷ mol L⁻¹ rutin was 1.2%. The proposed method was applied to determine rutin in tablet and urine sample. In addition, the IL/CPE exhibited a distinct advantage of simple preparation, surface renewal, good reproducibility and good stability.     

Graphdiyne and Ionic Liquid Composite Modified Gold Electrode for Sensitive Voltammetric Analysis of Rutin

It is significant to develop a point-of-care testing (POCT) method for rapid detection of medicinal molecules. In this paper, a graphdiyne (GDY)-ionic liquid (IL) composite was prepared via one-step facile ultrasound preparation process and then modified on gold (Au) electrode surface by simple casting method. Scanning electron microscopy and transmission electron microscopy were used to characterize the morphology of GDY-IL composite. Cyclic voltammetric results proved that GDY-IL composite on the electrode surface could effectively improve electron transfer rate, which meant that GDY-IL composite had high conductivity with big surface area. Finally, the modified electrode exhibited excellent performances for rutin detection with wider linear range (8.0×10⁻⁹ mol L⁻¹–2.0×10⁻⁶ mol L⁻¹ and 2.0×10⁻⁶ mol L⁻¹–1.5×10⁻⁴ mol L⁻¹) and lower detection limit (2.7 nmol L⁻¹, 3S₀/S). The Nafion/GDY-IL/Au electrode showed good sensitivity and high selectivity, which was satisfactory in analytical application to real samples. Therefore, the GDY-IL composite modified electrode has the potential applications in the POCT for electrochemical analysis of various medicinal molecules.     

Development of a Carbon Paste Electrode Modified with Reduced Graphene Oxide and an Imidazole Derivative for Simultaneous Determination of Biological Species of N‐acetyl‐L‐cysteine,Uric Acid and Dopamine

In this work, the modified carbon paste electrode (CPE) with an imidazole derivative 2‐(2,3 dihydroxy phenyl) 4‐methyl benzimidazole (DHPMB) and reduced graphene oxide (RGO) was used as an electrochemical sensor for electrocatalytic oxidation of N‐acetyl‐L‐cysteine (NAC). The electrocatalytic oxidation of N‐acetyl‐L‐cysteine on the modified electrode surface was then investigated, indicating a reduction in oxidative over voltage and an intensive increase in the current of analyte. The scan rate potential, the percentages of DHPMB and RGO, and the pH solution were optimized. Under the optimum conditions, some parameters such as the electron transfer coefficient (α) between electrode and modifier, and the electron transfer rate constant) k_s) in a 0.1 M phosphate buffer solution (pH=7.0) were obtained by cyclic voltammetry method. The diffusion coefficient of species (D) 3.96×10^?5 cm² s^?1 was calculated by chronoamperometeric technique and the Tafel plot was used to calculate α (0.46) for N‐ acetyl‐L‐cysteine. Also, by using differential pulse voltammetric (DPV) technique, two linear dynamic ranges of 2–18 µM and 18–1000 µM with the detection limit of 61.0 nM for N‐acetyl‐L‐cysteine (NAC) were achieved. In the co‐existence system of N‐acetyl‐L‐cysteine (NAC), uric acid (UA) and dopamine (DA), the linear response ranges for NAC, UA, and DA are 6.0–400.0 µM, 5.0–50.0 µM and 2.0–20.0 µM, respectively and the detection limits based on (C=3s_b/m) are 0.067 µM, 0.246 µM and 0.136 µM, respectively. The obtained results indicated that DHPMB/RGO/CPE is applicable to separate NAC, uric acid (UA) and dopamine (DA) oxidative peaks, simultaneously. For analytic performance, the mentioned modified electrode was used for determination of NAC in the drug samples with acceptable results, and the simultaneous determination of NAC, UA and DA oxidative peaks was investigated in the serum solutions, too.     

Electroless preparation and electrochemical behavior of a platinum-doped nickel hexacyanoferrate film–zinc modified electrode: catalytic ability of the electrode for electrooxidation of methanol

The use of a zinc substrate as an electrode and the modification of its surface by means of a thin film of platinum-doped nickel hexacyanoferrate (Pt-NiHCF) were developed. The modification conditions of the zinc surface including the electroless deposition of metallic nickel on the electrode surface from NiCl₂ solution, chemical derivatization of the deposited nickel to the NiHCF film in 0.5 M K₃[Fe(CN)₆] solution, and electrochemical penetration of metallic platinum into the modified film are described. The modified zinc electrodes prepared under optimum conditions show a well-defined redox couple due to the [Ni^IIFe^III/II(CN)₆]^1–/2– system. The effects of pH, the alkali metal cation, and the anion of the supporting electrolyte on the electrochemical characteristics of the modified electrode were studied in detail. The diffusion coefficients of hydrated alkali metal cations in the film (D), the transfer coefficient (), and the transfer rate constant for the electron (k_s) were calculated in the presence of some alkali metal cations. The electrocatalytic activity of the modified electrode for methanol oxidation was demonstrated. The stability of the modified electrode under various experimental conditions was investigated.     

Preparation and characterization of a new carbon paste electrode based on ketotifen–hexacyanoferrate

A new type of carbon paste electrode (CPE) was made using ketotifen fumarate (C₂₃H₂₃NO₅S; an antiasthmatic/antianaphylactic drug) and hexacyanoferrate. This electrode was constructed using an acidic solution of ketotifen fumarate and potassium hexacyanoferrate. For this purpose, ketotifen fumarate was dissolved in acidic solution (pH 1) and hexacyanoferrate was added by agitation, resulting in ketotifen–hexacyanoferrate (Ket–HCF) precipitate. The obtained precipitate was separated and introduced into carbon paste. The electrochemical behavior of Ket–HCF CPE was studied by cyclic voltammetry. A modified electrode shows one pair of peaks with surface-confined characteristics, with a 0.1-M phosphate buffer as supporting electrolyte. The effects of pH, alkali metal cations, and anions of supporting electrolytes on the electrochemical characteristics of modified electrodes were studied. The diffusion coefficients of hydrated K⁺ in film (D), the transfer coefficient (α), and the transfer rate constant for electrons (k _s) were determined.     

Preparation of Close‐Packed Silver Nanoparticles on Graphene to Improve the Enzyme Immobilization and Electron Transfer at Electrode in Glucose/O2 Biofuel Cell

In this study, chemical reduced graphene‐silver nanoparticles hybrid (AgNPs @CR‐GO ) with close‐packed AgNPs structure was used as a conductive matrix to adsorb enzyme and facilitate the electron transfer between immobilized enzyme and electrode. A facile route to prepare AgNPs @CR‐GO was designed involving in β ‐cyclodextrin (β ‐CD ) as reducing and stabilizing agent. The morphologies of AgNPs were regulated and controlled by various experimental factors. To fabricate the bioelectrode, AgNPs @CR‐GO was modified on glassy carbon electrode followed by immobilization of glucose oxidase (GOx ) or laccase. It was demonstrated by electrochemical testing that the electrode with close‐packed AgNPs provided high GOx loading (Γ =4.80 × 10⁻¹⁰ mol•cm⁻²) and fast electron transfer rate (k _s=5.76 s⁻¹). By employing GOx based‐electrode as anode and laccase based‐electrode as cathode, the assembled enzymatic biofuel cell exhibited a maximum power density of 77.437 μW •cm⁻² and an open‐circuit voltage of 0.705 V.     

Direct electron transfer reaction of glucose oxidase at bare silver electrodes and its application in analysis

The direct electron transfer reaction of glucose oxidase (GOx) at a bare silver electrode is verified. The electron transfer number n = 2, electron transfer coefficient α = 0.45 and rate constant of the electrochemical reaction K_s = 0.1 s⁻¹ are obtained. This communication presents a multimolecular adsorption model to explain the properties of the direct electron reaction between GOx and bare silver electrodes. The residual valence force may be an important factor to ensure a direct electron transfer reaction on the bare electrode. On the basis of the experimental fact that only biologically active GOx exhibits electrochemical activity in solution, a facile analytical method for analyzing the active GOx concentration is developed. The results determined correspond very well to that of a spectrometric method.     

Electrocatalysis via Direct Electrochemistry of Myoglobin Immobilized on Colloidal Gold Nanoparticles

The direct electron transfer between immobilized myoglobin (Mb) and colloidal gold modified carbon paste electrode was studied. The Mb immobilized on the colloidal gold nanoparticles displayed a pair of redox peaks in 0.1 M pH 7.0 PBS with a formal potential of –(0.108 ± 0.002) V (vs. NHE). The response showed a surface‐controlled electrode process with an electron transfer rate constant of (26.7 ± 3.7) s ^?1 at scan rates from 10 to 100 mV s^?1 and a diffusion‐controlled process involving the diffusion of proton at scan rates more than 100 mV s^?1. The immobilized Mb maintained its activity and could electrocatalyze the reduction of both hydrogen peroxide and nitrite. Thus, the novel renewable reagentless sensors for hydrogen peroxide and nitrite were developed, respectively. The activity of Mb with respect to the pseudo peroxidase with a K_M^app value of 0.65 mM could respond linearly to hydrogen peroxide concentration from 4.6 to 28 μM. The sensor exhibited a fast amperometric response to NO₂^? reduction and reached 93% of steady‐state current within 5 s. The linear range for NO₂^? determination was from 8.0 to 112 μM with a detection limit of 0.7 μM at 3σ.     

Chemically Modified Carbon Paste Electrode for Determination of Sulfate Ion by Potentiometric Method

Four Schiff base complexes of different metal ions, M=Cr(III), Mn(III), Fe(III), and Co(III), were studied to characterize their ability as sulfate ion carriers in carbon paste electrode (CPE). The modified CPE electrode with Schiff base complex of Cr(III), N,N′‐ethylenebis(5‐hydroxysalicylideneiminato) chromium(III) Chloride, showed good response characteristics to SO₄^2? ion. The proposed electrode exhibits a Nernstian slope of 28.9±0.4 mV per decade for SO₄^2? ion over a wide concentration range from 1.5×10^?6?4.8×10^?2 M, with a detection limit of 9.0×10^?7 M. The CPE electrode manifested advantages of relatively fast response time, suitable reproducibility and life time and, most important, good potentiometric selectivity relative to a wide variety of other common inorganic anions. The potentiometric response of the electrode is independent of the pH of the test solution in the pH range 4.0–9.0. The proposed electrode was used as an indicator electrode in potentiometric titration of sulfate with Ba²⁺ ion, the determination of zinc in zinc sulfate tablet and also determination of sulfate content of a mineral water sample.     

Electrochemical Behaviors of Adenosine‐5′‐triphosphate on Molecular Wire Modified Carbon Paste Electrode and Its Sensitive Detection

A new electrochemical method was proposed for the determination of adenosine‐5′‐triphosphate (ATP) based on the electrooxidation at a molecular wire (MW) modified carbon paste electrode (CPE), which was fabricated with diphenylacetylene (DPA) as the binder. A single well‐defined irreversible oxidation peak of ATP appeared on MW‐CPE with adsorption‐controlled process and enhanced electrochemical response in a pH 3.0 Britton‐Robinson buffer solution, which was due to the presence of high conductive DPA in the electrode. The electrochemical parameters of ATP were calculated with the electron transfer coefficient (α) as 0.54, the electron transfer number (n) as 1.9, the apparent heterogeneous electron transfer rate constant (k_s) as 2.67 × 10^?5 s^?1 and the surface coverage (Γ_T) as 4.15 × 10^?10 mol cm^?2. Under the selected conditions the oxidation peak current was proportional to ATP concentration in the range from 1.0 × 10^?7 mol L^?1 to 2.0 × 10^?3 mol L^?1 with the detection limit as 1.28 × 10^?8 mol L^?1 (3σ) by sensitive differential pulse voltammetry. The proposed method showed good selectivity without the interferences of coexisting substances and was successful applied to the ATP injection samples detection.