PCA/GC电极同时测定尿酸(UA)和抗坏血酸(AA)

制备聚肉桂酸(PCA)修饰电极(PCA/GC),研究尿酸(UA)和抗坏血酸(AA)在该电极上的电化学行为.结果表明,在UA和AA共存体系中,UA、AA在PCA/GC电极上氧化峰电流增大且峰电位分别负移至50mV、330mV,二者相差280mV,据此可同时检测UA和AA.在pH6.0磷酸盐缓冲液中,UA、AA的氧化峰电流与其浓度分别在2.0×10-6～1.0×10-4mol·L-1、2.0×10-5～6.0×10-4mol·L-1范围内呈线性关系.该电极重现性好,适用于尿样中UA的检测.     

柠檬酸修饰电极对抗坏血酸、多巴胺和尿酸的同时检测

研究柠檬酸(CA)修饰玻碳电极(CA/GC)在抗坏血酸(AA)、多巴胺(DA)和尿酸(UA)混合体系中的循环伏安(CV)行为.结果表明,AA、DA和UA在CA/GC电极上氧化峰电流增大,且三者氧化峰电位明显分离(ΔEp(DA,AA)=170 mV,ΔEp(DA,UA)=130 mV,ΔEp(AA,UA)=300 mV).据此,可同时检测AA、DA和UA.在优化的实验条件下,AA、DA和UA的氧化峰电流与其浓度分别在2.0×10-6～1.5×10-3mol.L-1,6.0×10-7～1.0×10-3mol.L-1和6.0×10-7～1.0×10-3mol.L-1范围内呈线性关系.该电极重现性好,可用于盐酸多巴胺针剂DA、VC片剂AA及人体尿液UA的测定.     

抗坏血酸在聚对羟基苯甲酸修饰玻碳电极上的催化电氧化行为

通过循环伏安(CV)制备了聚对羟基苯甲酸(poly-PHB)修饰的玻碳电极. 考察了电极对抗坏血酸(AA)电氧化的催化性能. 结果显示,聚对羟基苯甲酸修饰玻碳电极对AA氧化有很好的电催化作用. 在修饰电极上产生的峰电流比在未修饰电极上产生的氧化峰电流大4倍,氧化峰电位负移205 mV. 氧化峰电流与AA浓度在2.6×10-5～3.68 ×10-4 mol/L范围内呈线性关系,相关系数为0.998 4,检测限为5×10-6 mol/L(S/N=3). 在AA与多巴胺(DA)共存的体系中,能排除DA对抗坏血酸测定的干扰.     

芦丁修饰电极研究多巴胺的电化学响应

通过循环伏安法(CV)制备了芦丁修饰电极,研究多巴胺(DA)在修饰电极上的电化学行为.结果表明,芦丁修饰膜对DA的氧化有明显的催化作用,并且可以消除抗坏血酸(AA)对DA测定的干扰.DA的浓度在1.0×10-7～9.5×10-6 mol/L范围内与其氧化峰电流呈线性关系,相关系数为0.9996,检出限为1.0×10-8 mol/L.将该修饰电极用于注射液样品中DA的测定,结果表明该修饰电极可用于实际样品分析.     

Electrochemical Behavior of Dopamine at Poly( Methylene Blue)/Graphene Modified Glassy Carbon Electrode

利用电聚合方法在石墨烯修饰的玻碳电极表面制备了聚亚甲基蓝/石墨烯修饰电极( PMB/GH/GCE).采用循环伏安法(CV)和差分脉冲伏安法(DPV)研究了多巴胺(DA)和抗坏血酸(AA)在该修饰电极上的电化学行为.在pH 6.9的磷酸盐缓冲溶液中,DA和AA分别在0.208 V和-0.108 V处产生灵敏的氧化峰,与其在聚亚甲基蓝和石墨烯单层修饰电极上的电化学行为相比,两者的峰电流明显增加,峰电位差达316 mV.研究表明,电聚合方法使亚甲基蓝牢固地非共价修饰到石墨烯上,并产生协同增效作用,较好地提高了电极的灵敏度和分子识别性能,有利于在大量AA存在下实现对DA的选择性测定.在1.00×10-3 mol/L AA的存在下,DA的差分脉冲伏安法峰电流与其浓度在1.00×10--7～5.00×10-3 mol/L范围内呈良好的线性关系,检出限达1.00 × 10-6mol/L.将该方法用于盐酸多巴胺注射液的测定,结果满意.     

柠檬酸修饰(CA/GC)电极对多巴胺(DA)和肾上腺素(EP)同时检测

应用电沉积方法制备柠檬酸修饰电极(CA/GC), 差分脉冲法研究多巴胺(DA)和肾上腺素(EP)在该修饰电极上的电化学行为．结果表明, 两样品DA、EP在该电极的还原峰电位差380 mV, 而抗坏血酸(AA)在此电位区无还原峰, 因此可实现该修饰电极对DA和EP的同时检测, 而且高浓度AA不发生干扰．在pH 6.0的磷酸盐缓冲液中, DA和EP还原峰电流与其浓度分别在1.0×10-6 ~ 6.0×10-5 mol•L-1和2.0×10-6 ~ 6.0×10-5 mol•L-1 范围内呈线性关系．CA/GC电极制备简单, 重现性好, 可望用于多巴胺针剂(DA)和肾上腺素针剂(EP)的同时检测     

DA和AA在CPB现场修饰碳糊电极上的电化学行为及电分析方法

研究了多巴胺(Dopamine,DA)和抗坏血酸(Ascorbic acid,AA)在裸碳糊电极(Carbon Paste Electrode,CPE)和溴化十六烷基吡啶(Cetylpyrid bromide,CPB)现场修饰碳糊电极(CPB/CPE)上的电化学行为。与CPE相比,DA在CPB/CPE上与CPB产生了静电排斥作用,氧化峰电流减小,氧化峰电位正移;AA和CPB产生了静电吸引作用,氧化峰电流增大,氧化峰电位负移。循环伏安法研究表明,在DA和AA共存体系中,DA和AA的氧化峰电位相差约340 mV,以此建立了DA和AA的电化学同时测定方法。微分脉冲伏安法研究结果表明,DA和AA氧化峰电流和其相应浓度在1.0×10-5~5.0×10-3mol/L的范围内呈良好的线性关系。本方法也可用于DA和AA共存体系中选择性测定DA。在100倍AA共存时DA的检出限为2.0×10-6mol/L,CPB修饰碳糊电极直接用于市售针剂中DA含量的测定,所得结果令人满意。     

氮掺杂碳纳米管修饰电极的电化学行为

制备了氮掺杂改性的碳纳米管, 并用循环伏安法(CV)测定了多巴胺(DA)和抗坏血酸(AA)在不同氮含量的碳纳米管修饰电极上的电化学行为. 结果表明, 氮掺杂碳纳米管修饰电极对AA和DA有不同的电催化行为, 其中高氮含量修饰电极对AA的催化作用强, 而低氮含量修饰电极对DA的催化作用强. 微分脉冲伏安法(DPV)的结果显示, DA的氧化峰电流与其浓度在5.0×10^－6～2.0×10^－4 mol/L范围内呈良好的线性关系, 检出限达1.64×10^－6 mol/L (S/N＝3); AA氧化峰电流与其浓度在3.0×10^－5～1.0×10^－2 mol/L范围内呈良好的线性关系, 检出限达3.26×10^－6 mol/L (S/N＝3). 该修饰电极在AA大量存在(AA浓度为DA浓度两万倍)时可选择性地实现多巴胺的测定而不造成干扰.     

聚对氨基苯磺酸/氧化石墨烯修饰电极同时测定多巴胺和抗坏血酸

用循环伏安法制备了聚对氨基苯磺酸/氧化石墨烯修饰玻碳电极(PABSA/GO/GCE),研究了多巴胺(DA)和抗坏血酸(AA)在该修饰电极上的电化学行为,并建立了同时测定多巴胺和抗坏血酸电化学分析新方法,相对于裸玻碳电极,该电极测定DA和AA的峰电流明显增加。实验结果表明:在实验条件下,DA测定的线性范围为0.50～300μmol/L;检出限为5.0μmol/L。AA测定的线性范围是0.10～2.4 mmol/L,检出限为0.50μmol/L。     

桑色素/石墨烯修饰电极的制备及对多巴胺的选择性灵敏测定

在石墨烯纳米片修饰电极(GN/GCE)上,通过电聚合的方法制备了新颖的桑色素/石墨烯复合修饰电极(M/GN/GCE).以多巴胺(DA)和抗坏血酸(AA)为模型化合物,运用循环伏安法(CV)和差示脉冲伏安法(DPV)考察了该复合修饰电极的电催化行为.在pH 7.0的PBS中,DA和AA分别在0.172 V和-0.183 V产生氧化峰,峰位差达355 mV.与单一修饰电极(桑色素修饰电极(M/GCE)、石墨烯修饰电极(GN/GCE)及裸玻碳电极(GCE))相比,DA在M/GN/GCE上的峰电流显著增大.在优化的实验条件下,DA在2.0×l0-8～5.5×10-4 mol/L浓度范围内与其峰电流具有良好的线性关系,检出限达9.0×10-9 mol/L.     

Electrochemical behavior of dopamine and ascorbic acid at osmium(II) complex cationic monolayer modified gold electrodes.

The electrooxidation of dopamine (DA) and ascorbic acid (AA) was studied using gold electrodes modified by a cationic self-assembled monolayer of [Os(bpy)2(bpy-(CH2),3SH)]2+ by cyclic voltammetry. At an [Os(bpy)2(bpy-(CH2)13SH)]2+/Au electrode, the oxidation peak of DA shifted to a much more positive potential as compared with that of a bare gold electrode, while the oxidation peak potential of AA showed a slightly negative shift due to their different electrostatic interactions with the cationic monolayer. Thus, a sufficient potential difference was achieved for distinguishing the electrochemical responses of DA and AA. However, when CH3(CH2)11SH was mixed into the cationic monolayer, the enhanced packing of the mixed monolayer blocked the access of DA or AA to the electrode, resulting in further positive shifts for both oxidation-peak potentials.     

Polystyrene sulphonate wrapped multiwalled carbon nanotubes modified graphite electrode for simultaneous determination of ascorbic acid, dopamine and uric acid

Graphite electrode is modified by casting multi-walled carbon nanotubes (MWCNTs) wrapped with polystyrene sulphonate (PSS) onto the surface of the bare graphite electrode. The modified electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The behavior of the modified electrode towards the oxidation of ascorbic acid (AA), dopamine (DA) and uric acid (UA) has been determined by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA). The modified electrode showed better electrocatalytic activity towards AA, DA and UA compared to bare graphite electrode. The electrochemical oxidation signals of AA, DA and UA are well separated into three distinct peaks with peak potential difference of 222, 128 and 350 mV between AA-DA, DA-UA and AA-UA respectively in CV studies and corresponding peak potential separation in DPV are 228, 120 and 348 mV. This modified electrode was successfully used for simultaneous determination of AA, DA and UA in ternary mixture.     

Simultaneous electroanalysis of dopamine and ascorbic acid using poly (N,N-dimethylaniline)-modified electrodes

Glassy carbon (GC) electrode is modified with an electropolymerized film of N,N-dimethylaniline (DMA). This polymer (PDMA) film-coated GC electrode is used to electrochemically detect dopamine (DA) in the presence of ascorbic acid (AA). Polymer film has the positive charge in its backbone, and in neutral solution DA exists as the positively charged species whereas AA exists as the negatively charged one. In cyclic voltammetric measurements, favorable ionic interaction (i.e., electrostatic attraction) between AA and PDMA film causes a large negative shift of the oxidation potential for AA compared to that at the bare electrode. Oxidation potential for DA is positively shifted due to the electrostatic repulsion. The PDMA film shows hydrophobicity by incorporating uncharged hydroquinone molecule within the film. DA is also incorporated into the film due to hydrophobic attraction even though DA has a positive charge. The responses of DA and AA at polymer-modified electrodes largely change with the concentration of the monomer (i.e., 0.2, 0.1 and 0.05 M DMA) used in electropolymerization and thus with the film thickness. Hydrophobicity of the polymer film shows great influence on the voltammetric responses of both DA and AA. In square wave voltammetric measurements, the PDMA film-coated electrode can separate the DA and AA oxidation potentials by about 300 mV and can detect DA at its low concentration (e.g., 0.2 microM) in the presence of 1000 times higher concentration of AA, which is close to the physiological level. AA oxidizes at more negative potential than DA. The electrode response is not affected by the oxidized product of AA. So unlike the bare electrode, the fouling effect as well as the catalytic oxidation of AA by the oxidized form of DA are eliminated at the PDMA film-coated GC electrode. The electrode exhibits the stable and sensitive response to DA.     

Electrochemical determination of dopamine and ascorbic acid at a novel gold nanoparticles distributed poly(4-aminothiophenol) modified electrode

A modified electrode is fabricated by embedding gold nanoparticles into a layer of electroactive polymer, poly(4-aminothiophenol) (PAT) on the surface of glassy carbon (GC) electrode. Cyclic voltammetry (CV) is performed to deposit PAT and concomitantly deposit Au nanoparticles. Field emission transmission electron microscopic image of the modified electrode, PAT-Au_nano-ME, indicates the presence of uniformly distributed Au nanoparticles having the sizes of 8-10 nm. Electrochemical behavior of the PAT-Au_nano-ME towards detection of ascorbic acid (AA) and dopamine (DA) is studied using CV. Electrocatalytic determination of DA in the presence of fixed concentration of AA and vice versa, are studied using differential pulse voltammetry (DPV). PAT-Au_nano-ME exhibits two well defined anodic peaks at the potential of 75 and 400 mV for the oxidation of AA and DA, respectively with a potential difference of 325 mV. Further, the simultaneous determination of AA and DA is studied by varying the concentration of AA and DA. PAT-Au_nano-ME exhibits selectivity and sensitivity for the simultaneous determination of AA and DA without fouling by the oxidation products of AA or DA. PAT and Au nanoparticles provide synergic influence on the accurate electrochemical determination of AA or DA from a mixture having any one of the component (AA or DA) in excess. The practical analytical utilities of the PAT-Au_nano-ME are demonstrated by the determination of DA and AA in dopamine hydrochloride injection and human blood serum samples.     

Simultaneous determination of dopamine and ascorbic acid at a poly(toluidine blue) modified electrode.

A novel polymer modified electrode is discussed in this paper. This resulting electrode can catalyze remarkably toward the electrochemical oxidations of dopamine (DA) and ascorbic acid (AA). Moreover, it can clearly discriminate the electrochemical oxidations of DA from that of AA based on their semi-derivative voltammograms. Hence, a simultaneous determination of DA and AA based on semi-derivative voltammetry at a poly(toluidine blue) modified electrode is suggested. The detection linear range for DA is 0.4 micromol L(-1)-1.5 mmol L(-1), and AA 0.2 micromol L(-1)-2.4 mmol L(-1), respectively. The resulting modified electrode was tentatively used to determine DA and AA in brain tissue.     

Poly (3-(3-pyridyl) acrylic acid) modified glassy carbon electrode for simultaneous determination of dopamine, ascorbic acid and uric acid

Trans-3-(3-pyridyl) acrylic acid (PAA) was deposited on glassy carbon electrode (GCE) by electropolymerization in pH 7.0 phosphate buffer solution (PBS). The poly (3-(3-pyridyl) acrylic acid) (PPAA) film modified glassy carbon electrode shows an excellent electrochemical response for dopamine (DA), ascorbic acid (AA) and uric acid (UA). The cyclic voltammetry oxidation peaks for DA and AA, DA and UA, AA and UA are separated by 150 mV, 130 mV and 280 mV, respectively. This permits the simultaneous determination of AA, DA and UA. The interference of AA with the determination of DA could be eliminated because of the electrostatic interaction between DA cations and the negatively charged PPAA film at pH 7.0. The anodic peak currents of DA, AA and UA increase linearly with concentration in the range of 1-40 micromol L(-1), 10-400 micromol L(-1) and 1.6-80 micromol L(-1), respectively, with a correlation coefficient (r) always higher than 0.998. The detection limit is 0.06 micromol L(-1), 0.8 micromol L(-1) and 1.1 micromol L(-1) for DA, AA and UA, respectively.     

Simultaneous voltammetric measurement of ascorbic acid and dopamine on poly(caffeic acid)-modified glassy carbon electrode

A poly(caffeic acid) thin film was deposited on the surface of a glassy carbon electrode by potentiostatic technique in an aqueous solution containing caffeic acid. The poly(caffeic acid)-modified electrode was used for the determination of ascorbic acid (AA), dopamine (DA), and their mixture by cyclic voltammetry. This modified electrode exhibited a potent and persistent electron-mediating behavior followed by well-separated oxidation peaks toward AA and DA at a scan rate of 10 mV s⁻¹ with a potential difference of 135 mV, which was large enough to determine AA and DA individually and simultaneously. The catalytic peak current obtained was linearly dependent on the AA and DA concentrations in the range of 2.0 × 10⁻⁵−1.2 × 10⁻³ and 1.0 × 10⁻⁶−4.0 × 10⁻⁵ mol L⁻¹ in 0.15 mol L⁻¹ phosphate buffer (pH 6.64). The detection limits for AA and DA were 9.0 × 10⁻⁶ and 4.0 × 10⁻⁷ mol L⁻¹, respectively. The modified electrode shows good sensitivity, selectivity, and stability and has been applied to the determination of DA and AA in real samples with satisfactory results.     

Simultaneous determination of dopamine and ascorbic acid on poly (3,4-ethylenedioxythiophene) modified glassy carbon electrode

Detection of dopamine (DA) in the presence of excess of ascorbic acid (AA) has been demonstrated using a conducting polymer matrix, poly (3,4-ethylenedioxythiophene) (PEDOT) film in neutral buffer (PBS 7.4) solution. The PEDOT film was deposited on a glassy carbon electrode by electropolymerization of EDOT from acetonitrile solution. Atomic force microscopy studies revealed that the electrodeposited film was found to be approximately 100 nm thick with a roughness factor of 2.6 nm. Voltammetric studies have shown catalytic oxidation of DA and AA on PEDOT modified electrode and can afford a peak potential separation of ∼0.2 V. It is speculated that the cationic PEDOT film interacts with the negatively charged ascorbate anion through favorable electrostatic interaction, which results in pre-concentration at a less anodic value. The positively charged DA tends to interact with the hydrophobic regions of PEDOT film through hydrophobic–hydrophobic interaction thus resulting in favorable adsorption on the polymer matrix. Further enhancement in sensitivity to micro molar level oxidation current for DA/AA oxidation was achieved by square wave voltammetry (SWV) which can detect DA at its low concentration of 1 μM in the presence of 1000 times higher concentration of AA (1 mM). Thus the PEDOT modified electrode exhibited a stable and sensitive response to DA in the presence of AA interference.     

Selective Electrochemical Determination of Dopamine with Molecularly Imprinted Poly(Carbazole‐co‐Aniline) Electrode Decorated with Gold Nanoparticles

Dopamine (DA) is a significant neurotransmitter in the central nervous system, coexisting with uric acid (UA) and ascorbic acid (AA). UA and AA are easily oxidizable compounds having potentials close to that of DA for electrochemical analysis, resulting in overlapping voltammetric response. In this work, a novel molecularly imprinted (MI) electrochemical sensor was proposed for selective determination of DA (in the presence of up to 80‐fold excess of UA and AA), relying on gold nanoparticles (Au_nano)‐decorated glassy carbon (GC) electrode coated with poly(carbazole (Cz)‐co‐aniline (ANI)) copolymer film incorporating DA as template (DA imprinted‐GC/P(Cz‐co‐ANI)‐Au_nano electrode, DA‐MIP‐Au_nano electrode). The DA recognizing sensor electrode showed great electroactivity for analyte oxidation in 0.2 mol L^?1 pH 7 phosphate buffer. Square wave voltammetry (SWV) was performed within 10^?4–10^?5 mol L^?1 of DA, of which the oxidation peak potential was observed at 0.16 V. The limit of detection (LOD) and limit of quantification (LOQ) were 2.0×10^?6 and 6.7×10^?6 mol L^?1, respectively. Binary and ternary synthetic mixtures of DA‐UA, DA‐AA and DA‐UA‐AA yielded excellent recoveries for DA. Additionally, DA was quantitatively recovered from a real sample of bovine serum spiked with DA, and determined in concentrated dopamine injection solution. The developed SWV method was statistically validated against a literature potentiodynamic method using a caffeic acid modified‐GC electrode.