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1.
A surface‐renewable tris(1, 10‐phenanthroline‐5, 6‐dione) iron (D) hexafluorophosphate (FePD) modified carbon ceramic electrode was constructed by dispersing FePD and graphite powder in methyltrimethoxysilane (MTMOS) based gels. The FePD‐modified electrode presented pH‐dependent voltammetric behavior, and its peak currents were diffusion‐controlled in 0.1 mol/L Na2SO4 + H2SO4 solution (pH = 0.4). In the presence of iodate, dear electrocatalytic reduction waves were observed and thus the chemically modified electrode was used as an amperometric sensor for iodate in common salt. The linear range, sensitivity, detection limit and response time of the iodate sensor were 5 × 10?6–1 × 10?2 mol/L, 7.448 μA·L/ mmol, 1.2 × 10?6 mol/L and 5 s, respectively. A distinct advantage of this sensor is its good reproducibility of surface‐renewal by simple mechanical polishing.  相似文献   

2.
《Electroanalysis》2005,17(4):343-347
The adsorptive voltammetric behavior of the gallium‐alizarin red S (ARS) complex in NH4OAc‐HCl buffer at a carbon paste electrode(CPE) was investigated. The results showed that the complex can be adsorbed on the surface of the CPE, yielding one reduction peak at ?0.52 V(vs. SCE), corresponding to the irreversible reduction of the ligand, ARS, bonded in the complex. The optimal experimental conditions include the use of 0.10 mol L?1 ammonium acetate buffer(pH 4.5), 1.0×10?5 mol L?1 ARS, an accumulation potential of ?0.05 V, an accumulation time of 180 s ,a rest time of 10 s, a scan rate of 200 mV s?1and a second‐order derivative linear scan mode. The peak current is proportional to the concentration of gallium(III) over the range 0.02–6.0 μg L?1, with the detection limit of 0.01 μg L?1 for an accumulation time of 180 s. The method was applied to the determination of gallium in food samples with satisfactory results.  相似文献   

3.
As an alternative selection of electrocatalytic surface modifier, the electrochemically generated copper oxides is re‐ investigated by using cyclic voltammetry (CV), scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). Interesting phenomena have been found, which indicate that the electrodeposition from the Cu2+ solution under cyclic voltammetric conditions can generate a transparent Cu(OH)2 crystalline on the surface of glassy carbon electrodes, and this crystalline can be further transferred to a novel cubic opaque CuO crystalline of about 300 nm in size by second step of cyclic voltammetry in pH 12 NaOH solution. The final electrode (denoted as nano‐CuO/GCE) can catalyze the oxidation (as well as the reduction) of H2O2 in basic solutions. It shows pH dependent three‐part catalytic mechanism in the range from pH 7 to pH 14. In 0.10 mol/L NaOH solution, the amperometric response at 0.15 V (vs. SCE) can give a current sensitivity as high as 139 mA/(mol·L?1) in the rage of 5.0×10?7?6.0×10?4 mol/L with a lower detection limit (s/n=3) of 2.5×10?8 mol/L, and a current sensitivity of 78.4 mA/(mol·L?1) in the rage of 6.0×10?4–2.0×10?3 mol/L. This electrode also has excellent reproducibility and stability. The mechanisms for the two steps of preparation and the catalytic reactions are proposed. The nano‐CuO crystalline modified electrode may have more applications in the field of electrochemical sensing.  相似文献   

4.
This work demonstrates gold nanoparticles (AuNPs)/functionalized multiwalled carbon nanotubes (f‐MWCNT) composite film modified gold electrode via covalent‐bonding interaction self‐assembly technique for simultaneous determination of salsolinol (Sal) and uric Acid (UA) in the presence of high concentration of ascorbic acid (AA). In pH 7.0 PBS, the composite film modified electrode exhibits excellent voltammetric response for Sal and UA, while AA shows no voltammetric response. The oxidation peak current is linearly increased with concentrations of Sal from 0.24–11.76 μmol L?1 and of UA from 3.36–96.36 μmol L?1, respectively. The detection limits of Sal and UA is 3.2×10?8 mol L?1 and 1.7×10?7 mol L?1 , respectively.  相似文献   

5.
A new method for the determination of trace copper was described. A multiwalled carbon nanotube modified carbon paste electrode was prepared and the adsorptive voltammetric behavior of copper‐alizarin red S (ARS) complex at the modified electrode was investigated. By use of the second‐order derivative linear sweep voltammetry, it was found that in 0.04 mol/L acetate buffer solution (pH 4.2) containing 4×10?6 mol/L ARS, when accumulation potential is 0 mV, accumulation time is 60 s and scan rate is 100 mV/s, the complex can be adsorbed on the surface of the electrode, yielding one sensitive reduction peak at ?172 mV (vs. SCE). The peak current of the complex is proportional to the concentration of Cu(II) in the range of 2.0×10?11–4.0×10?7 mol L?1 with a detection limit (S/N=3) of 8.0×10?12 mol/L (4 min accumulation). The proposed method was successfully applied to the determination of copper in biological samples with satisfactory results, the recoveries were found to be 96%–102%.  相似文献   

6.
In this paper a graphene (GR) modified carbon ionic liquid electrode (CILE) was fabricated and used as the voltammetric sensor for the sensitive detection of catechol. Due to the specific physicochemical characteristics of GR such as high surface area, excellent conductivity and good electrochemical properties, the modified electrode exhibits rapid response and strong catalytic activity with high stability toward the electrochemical oxidation of catechol. A pair of well‐defined redox peaks appeared with the anodic and the cathodic peak potential located at 225 mV and 133 mV (vs.SCE) in pH 6.5 phosphate buffer solution, respectively. Electrochemical behaviors of catechol on the GR modified CILE were carefully investigated and the electrochemical parameters were calculated with the results of the electrode reaction standard rate constant (ks) as 1.24 s?1, the charge transfer coefficient (α) as 0.4 and the electron transfer number (n) as 2. Under the selected conditions the differential pulse voltammetric peak current increased linearly with the catechol concentrations in the range from 1.0 × 10‐7 to 7.0 × 10?4mol L‐1 with the detection limit as 3.0 × 10?8mol L‐1 (3σ). The proposed method was further applied to the synthetic waste water samples determination with satisfactory results  相似文献   

7.
The electrochemical oxidation of promethazine hydrochloride was made on highly boron‐doped diamond electrodes. Cyclic voltammetry experiments showed that the oxidation mechanisms involved the formation of an adsorbed product that is more readily oxidized, producing a new peak with lower potential values whose intensity can be increased by applying the accumulation potential for given times. The parameters were optimized and the highest current intensities were obtained by applying +0.78 V for 30 seconds. The square‐wave adsorptive voltammetry results obtained in BR buffer showed two well‐defined peaks, dependent on the pH and on the voltammetric parameters. The best responses were obtained at pH 4.0, frequency of 50 s?1, step of 2 mV, and amplitude of 50 mV. Under these conditions, linear responses were obtained for concentrations from 5.96×10?7 to 4.76×10?6 mol L?1, and calculated detection limits of 2.66×10?8 mol L?1 (8.51 μg L?1) for peak 1 and of 4.61×10?8 mol L?1 (14.77 μg L?1) for peak 2. The precision and accuracy were evaluated by repeatability and reproducibility experiments, which yielded values of less than 5.00% for both voltammetric peaks. The applicability of this procedure was tested on commercial formulations of promethazine hydrochloride by observing the stability, specificity, recovery and precision of the procedure in complex samples. All results obtained were compared to recommended procedure by British Pharmacopeia. The voltammetric results indicate that the proposed procedure is stable and sensitive, with good reproducibility even when the accumulation steps involve short times. It is therefore very suitable for the development of the electroanalytical procedure, providing adequate sensitivity and a reliable method.  相似文献   

8.
A method for the voltammetric determination of vanadium using a carbon paste electrode (CPE) was described. The new procedure is based on the adsorptive accumulation of the V(V)‐alizarin red S(ARS) complex onto the surface of the CPE, followed by the electrochemical reduction of adsorbed species. The optimal experimental conditions include the use of 0.10 mol/L acetate buffer (pH 5.1), 1.0×10?5 mol/L ARS, an accumulation potential of ?0.10 V (versus SCE), an accumulation time of 2 min, a scan rate of 200 mV/s and a second‐order derivative linear scan mode. The reduction peak for the complex appears at ?0.52 V. The peak current is proportional to the concentration of V(V) over the range of 0.10–15.0 μg/L, and the detection limit is 0.04 μg/L for a 2 min adsorption time. The relative standard deviations(n=8) for 2.0 and 0.50 μg/L V(V) are 3.1 and 4.7%, respectively. The proposed method was applied to the determination of vanadium in water samples.  相似文献   

9.
A sensitive square‐wave voltammetry method was developed to determine cholecalciferol (vitamin D3) in pharmaceutical products at boron‐doped diamond electrode as a working electrode. Vitamin D3 provided a well‐defined voltammetric peak at around +1.00 V (vs. Ag/AgCl, 3.5 mol dm?3) in 0.02 mol dm?3 Britton‐Robinson buffer pH 5.0 prepared in 50 % ethanol. The influence of various factors such as type and pH of the supporting electrolyte, scan rate and square‐wave parameters were studied and optimized. Under optimum conditions, the oxidation peak current increased linearly with the concentration of vitamin D3 over the range of 2 to 200 μmol dm?3. The calculated limit of detection and limit of quantitation were 0.17 μmol dm?3 and 0.51 μmol dm?3, respectively. The boron‐doped diamond electrode exhibited specific recognition capability for cholecalciferol amongst possible interferences, and the determination of vitamin D3 was possible in samples such as commercial pharmaceutical products without complicated sample pretreatments.  相似文献   

10.
《Electroanalysis》2006,18(3):253-258
The anodic voltammetric behavior of carbaryl on a boron‐doped diamond electrode in aqueous solution is reported. The results, obtained by square‐wave voltammetry at 0.1 mol L?1 Na2SO4 and pH 6.0, allow the development of a method to determine carbaryl, without any previous step of extraction, clean‐up, preconcentration or derivatization, in the range 2.5–30.0×10?6 mol L?1, with a detection limit of 8.2±0.2 μg L?1 in pure water. The analytical sensitivity of this electrochemical method diminished slightly, from 3.07 mA mmol?1 L to 2.90 mA mmol?1L, when the electrolyte was prepared with water samples collected from two polluted points in an urban creek. In these conditions, the recovery efficiencies obtained were around 104%. The effect of other pesticides (fenthion and 4‐nitrophenol) was evaluated and found to exert a negligible influence on carbaryl determination. The square‐wave voltammetric data obtained for carbaryl were typical of an irreversible electrode process with mass transport control. The combination of square‐wave voltammetry and diamond electrodes is an interesting and desirable alternative for analytical determinations.  相似文献   

11.
The present work describes the individual, selective and simultaneous quantification of acetaminophen (ACP) and tramadol hydrochloride (TRA) using a modification‐free boron‐doped diamond (BDD) electrode. Cyclic voltammetric measurements revealed that the profile of the binary mixtures of ACP and TRA were manifested by two irreversible oxidation peaks at about +1.04 V (for ACP) and +1.61 V (for TRA) in Britton‐Robinson (BR) buffer pH 3.0. TRA oxidation peak was significantly improved in the presence of anionic surfactant, sodium dodecyl sulfate (SDS), while ACP signal did not change. By employing square‐wave stripping mode in BR buffer pH 3.0 containing 8×10?4 mol L?1 SDS after 30 s accumulation under open‐circuit voltage, the BDD electrode could be used for quantification of ACP and TRA simultaneously in the ranges 1.0–70 μg mL?1 (6.6×10?6–4.6×10?4 mol L?1) and 1.0–70 μg mL?1 (3.3×10?6–2.3×10?4 mol L?1), with detection limits of 0.11 μg mL?1 (7.3×10?7 mol L?1) and 0.13 μg mL?1 (4.3×10?7 mol L?1), respectively. The practical applicability of the proposed approach was tested for the individual and simultaneous quantification of ACP and/or TRA in the pharmaceutical dosage forms.  相似文献   

12.
Chuanyin Liu  Jiming Hu 《Electroanalysis》2008,20(10):1067-1072
Hemoglobin was entrapped in composite electrodeposited chitosan‐multiwall carbon nanotubes (MCNTs) film by assembling gold nanoparticles and hemoglobin step by step. In phosphate buffer solution (pH 7), a pair of well‐defined and quasireversible redox peaks appeared with formal potential at ?0.289 V and peak separation of 100 mV. The redox peaks respected for the direct electrochemistry of hemoglobin at the surface of chitosan‐MCNTs‐gold nanoparticles modified electrode. The parameters of experiments have also been optimized. The composite electrode showed excellent electrocatalysis to peroxide hydrogen and oxygen, the peak current was linearly proportional to H2O2 concentration in the range from 1×10?6 mol/L to 4.7×10?4 mol/L with a detection limit of 5.0×10?7 mol/L, and this biosensor exhibited high stability, good reproducibility and better selectivity. The biosensor showed a Michaelis–Menten kinetic response as H2O2 concentration is larger than 5.0×10?4 mol/L, the apparent Michaelis–Menten constant for hydrogen peroxide was calculated to be 1.61 μmol/L.  相似文献   

13.
An ionic liquid N‐hexylpyridinium hexafluorophosphate (HPPF6) modified carbon paste electrode was fabricated for the sensitive voltammetric determination of adenosine in this paper. Carbon ionic liquid electrode (CILE) was prepared by mixing graphite powder and HPPF6 together and the CILE was characterized by scanning electron microscopy (SEM) and electrochemical methods. The electrochemical behaviors of adenosine on the CILE were studied carefully. Compared with the traditional carbon paste electrode (CPE), a small negative shift of the oxidation peak potential appeared with greatly increase of the oxidation peak current, which indicated the presence of ionic liquid in the carbon paste not only as the binder but also as the modifier and promoter. Under the optimal conditions the oxidation peak current increased with the adenosine concentration in the range from 1.0×10?6 mol/L to 1.4×10?4 mol/L with the detection limit of 9.1×10?7 mol/L (S/N=3) by differential pulse voltammetry. The proposed method was applied to the human urine samples detection with satisfactory results.  相似文献   

14.
An adsorptive differential pulse stripping method for the simultaneous determination of lead and tin is proposed. The procedure involves an adsorptive accumulation of lead and tin on a hanging mercury drop electrode (HMDE), followed by oxidation of adsorbed lead and tin by voltammetric scan using differential pulse modulation. The optimum experimental conditions are: 0.2 mol L?1 HNO3, accumulation potential of ?900 mV versus Ag/AgCl, accumulation time of 200 s, scan rate of 20 mV s?1 and pulse height of 80 mV. Lead and tin peak currents were observed in the same potential region at about ?400 mV. The simultaneous determination of lead and tin by using voltammetry is a difficult problem in analytical chemistry, due to voltammogram interferences. The resolution of a mixture of lead and tin by the application of orthogonal signal correction‐partial least squares (OSC‐PLS) was performed. The linear dynamic ranges were 0.003‐0.35 and 0.008‐0.50 μg mL?1 and detection limits were land 3 ng mL?1 for lead and tin, respectively. The RMSEP for lead and tin with OSC and without OSC were 2.8737, 6.0557 and 8.0941, 9.5151, respectively. The capability of the method for the analysis of real samples was evaluated by the determination of lead and tin in water samples with satisfactory results.  相似文献   

15.
The SAM nanoSe0/Vc/SeCys‐film modified Au electrode has been prepared to determine selenocystine and selenomethionine. The AFM and SEM showed the special three‐dimensional (3D) network structure of the sol‐gel films. The affinity between nanoparticles and biomolecules created special chemical characters analyzed by the XRD and fluorescence. The modified electrode was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The modified films partly had resistance in the charge transduction of Fe(CN) , but the less electron‐transfer resistance. Differential pulse voltammetric (DPV) determination of selenoamino acids using SAM nanoSe0/Vc/SeCys‐film modified Au electrode was presented. In PBS (pH 7.0)+0.1 mol L?1 NaClO4 solution, selenoamino acids yielded a sensitive reduction peak at about +400±50 mV. The peak current had a linear relationship with the concentration of selenoamino acids in the range of 5.0×10?8–1.0×10?5 mol L?1, and a 3σ detection limit of selenoamino acids was 1.2×10?8 mol L?1. The relative standard deviation of DPV signals of 0.50×10?6 mol L?1 selenoamino acids was 3.8% (n=8) using the same electrode and was 4.4% (n=5) when using three modified electrodes prepared at different times. The content of selenoamino acids in the organo‐selenium powder were determined by DPV. The results showed 71.5 μg g?1 of SeCys and 65.1 μg g?1 of SeMet in the organo‐selenium powder.  相似文献   

16.
A new hemoglobin (Hb) and room temperature ionic liquid modified carbon paste electrode was constructed by mixing Hb with 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF6) and graphite powder together. The Hb modified carbon ionic liquid electrode (Hb‐CILE) was further characterized by FT‐IR spectra, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Hb in the carbon ionic liquid electrode remained its natural structure and showed good direct electrochemical behaviors. A pair of well‐defined quasireversible redox peaks appeared with the apparent standard potential (E′) as ?0.334 (vs. SCE) in pH 7.0 phosphate buffer solution (PBS). The electrochemical parameters such as the electron transfer number (n), the electron transfer coefficient (α) and the heterogeneous electron transfer kinetic constant (ks) of the electrode reaction were calculated with the results as 1.2, 0.465 and 0.434 s?1, respectively. The fabricated Hb‐CILE exhibited excellent electrocatalytic activity to the reduction of H2O2. The calibration range for H2O2 quantitation was between 8.0×10?6 mol/L and 2.8×10?4 mol/L with the linear regression equation as Iss (μA)=0.12 C (μmol/L)+0.73 (n=18, γ=0.997) and the detection limit as 1.0×10?6 mol/L (3σ). The apparent Michaelis–Menten constant (KMapp) of Hb in the modified electrode was estimated to be 1.103 mmol/L. The surface of this electrochemical sensor can be renewed by a simple polishing step and showed good reproducibility.  相似文献   

17.
In this paper a room temperature ionic liquid 1‐butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF6) was used as binder for the construction of carbon ionic liquid electrode (CILE) and a new electrochemical biosensor was developed for determination of H2O2 by immobilization of hemoglobin (Hb) in the composite film of Nafion/nano‐CaCO3 on the surface of CILE. The Hb modified electrode showed a pair of well‐defined, quasi‐reversible redox peaks with Epa and Epc as ?0.265 V and ?0.470 V (vs. SCE). The formal potential (E°′) was got by the midpoint of Epa and Epc as ?0.368 V, which was the characteristic of Hb Fe(III)/Fe(II) redox couples. The peak to peak separation was 205 mV in pH 7.0 Britton–Robinson (B–R) buffer solution at the scan rate of 100 mV/s. The direct electrochemistry of Hb in the film was carefully investigated and the electrochemical parameters of Hb on the modified electrode were calculated as α=0.487 and ks=0.128 s?1. The Nafion/nano‐CaCO3/Hb film electrode showed good electrocatalysis to the reduction of H2O2 in the linear range from 8.0 to 240.0 μmol/L and the detection limit as 5.0 μmol/L (3σ). The apparent Michaelis–Menten constant (KMapp) was estimated to be 65.7 μmol/L. UV‐vis absorption spectroscopy and FT‐IR spectroscopy showed that Hb in the Nafion/nano‐CaCO3 composite film could retain its native structure.  相似文献   

18.
The electrochemical oxidation of ibuprofen at a boron‐doped diamond electrode (BDDE) and its voltammetric determination is reported for the first time. A well‐defined oxidation peak was observed at around 1.6 V in 0.1 mol L?1 H2SO4 solution with 10 % (v/v) ethanol at the BDDE surface activated by either cathodic or anodic pretreatments. A differential‐pulse voltammetric method for the determination of ibuprofen in pharmaceutical formulations was optimized with a detection limit of 5 µmol L?1 and compared with the British Pharmacopeia method.  相似文献   

19.
In this paper a carbon ionic liquid electrode (CILE) was fabricated by using ionic liquid 1‐ethyl‐3‐methylimidazolium ethylsulphate ([EMIM]EtOSO3) as the modifier and further used as the working electrode for the sensitive anodic stripping voltammetric detection of Pb2+. The characteristics of the CILE were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). In pH 4.5 NaAc‐HAc buffer Pb2+ was accumulated on the surface of CILE due to the extraction effect of IL and reduced at a negative potential (‐1.20 V). Then the reduced Pb was oxidized by differential pulse anodic stripping voltammetry with an obvious stripping peak appeared at ?0.67 V. Under the optimal conditions Pb2+ could be detected in the concentration range from 1.0 × 10?8 mol/L to 1.0 × 10?6 mol/L with the linear regression equation as Ip(μA) = ?0.103 C (μmol/L) + 0.0376 (γ = 0.999) and the detection limit as 3.0 × l0?9 mol/L (3σ). Interferences from other metal ions were investigated and Cd2+ could be simultaneously detected in the mixture solution. The proposed method was further applied to the trace levels of Pb2+ detection in water samples with satisfactory results.  相似文献   

20.
《Electroanalysis》2006,18(11):1075-1080
The voltammetric behavior of uric acid (UA) has been studied at a multiwalled carbon nanotube‐ionic liquid (i.e., 1‐butyl‐3‐methylimidazolium hexafluorophosphate, BMIMPF6) paste coated glassy carbon electrode (MWNTs‐BMIMPF6/GC). It is found that UA can effectively accumulate at this electrode and cause a sensitive anodic peak at about 0.49 V (vs. SCE) in pH 4.0 phosphate buffer solutions. Experimental parameters influencing the response of the electrode, such as solution pH and accumulation time, are optimized for uric acid determination. Under the optimum conditions, the anodic peak current is linear to UA concentration in the range of 1.0×10?8 M to 1.0×10?6 M and 2.0×10?6 M to 2.0×10?5 M. The detection limit is 5.0×10?9 M for 180 s accumulation on open circuit. The electrode can be regenerated by successively cycling in a blank solution for about 3 min and exhibits good reproducibility. A 1.0×10?6 M UA solution is measured for eight times using the same electrode regenerated after every determination, and the relative standard deviation (RSD) of the peak current is 3.2%. As for different electrodes fabricated by the same way the RSD (i.e., the electrode to electrode deviation) is 4.2%(n=9). This method has been applied to the determination of UA in human urine samples, and the recoveries are 99%–100.6%. In addition, comparison is made between MWNTs‐BMIMPF6/GC and MWNTs/GC. Results show that the MWNTs‐BMIMPF6/GC exhibits higher sensitivity, selectivity and ratio of peak current to background current.  相似文献   

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