石墨烯修饰玻碳电极伏安法测定酪氨酸

制备了石墨烯修饰玻碳电极,研究了酪氨酸在修饰电极上的电化学行为.优化了包括支持电解质、溶液pH、修饰剂用量、富集电位及时间等测定条件.在0.1 mol·L-1pH 7.0的磷酸盐缓冲溶液中,峰电流与酪氨酸的浓度在3×10-6～1.2×10-4mol·L-1的范围内呈良好的线性关系,检出限为2 × 10-7 mol·L-...     

胡椒碱在碳纳米管修饰电极上的电化学行为研究

研究了胡椒碱在碳纳米管修饰电极上的电化学行为,在pH为6.4的磷酸盐缓冲溶液中,胡椒碱在-1.12V(vs.SCE)处有一灵敏的还原峰.与裸电极相比,还原峰电位明显正移,峰电流显著增加,表明该修饰电极对胡椒碱的还原反应具有明显的催化作用.峰电流与胡椒碱的浓度在10-6～10-5mol/L范围内呈良好的线性关系(r=0.995),检出限为2.0×10-7mol/L.同时,计算了电荷转移数和扩散系数,考查了修饰电极的重现性,7次平行测量的RSD为4.96%.     

聚苏木精修饰玻碳电极测定酪氨酸

通过在玻碳电极上电聚合聚苏木精的方法制备了聚苏木精修饰电极,研究了酪氨酸在修饰电极上的电化学行为。在0.1 mol/L磷酸盐缓冲溶液(pH3.0)中,富集电位为-0.3 V,富集时间为180 s,氧化峰电流与酪氨酸的浓度在5.0×10-6～1.0×10-4mol/L的范围内呈良好的线性关系,检出限为3.0×10-7mo...     

The electrochemical behavior of dopamine at glassy carbon electrode modified by Nafion multiwalled carbon nanotubes

DFT (B3LY/6-31G (d, p) and B3LYP/cc-PVDZ) calculations are performed for deoxidized dopamine (DA_(R)) and its oxidized form (DA_(O)). The electrochemistry of dopamine (DA) was studied by cyclic voltammetry (CV) at a glassy carbon electrode modified by Nafion multiwalled carbon nanotubes (MWNTs) in phosphate buffers at pH 5.4, showing that the standard electrode potential of a half reaction for DA_(O), H⁺/DA_(R) is 0.74 V. This experimental standard electrode potential of the half reaction is consistent with those of 0.65 and 0.69 V calculated using the energies of solvation and the sum of the electronic and thermal free energies of DA_(R) and DA_(O). The frontier orbital theory and Mulliken charges of molecules explain the electrochemical behavior of CV at a modified electrode well. The effects of oxygen on DA_(R) in blood and drug are also discussed according to equilibrium theory. The modified electrode was successful for determination of the content of pharmaceutical DA. The text was submitted by the authors in English.     

对氯酚在碳纳米管修饰玻碳电极上的电化学行为研究

研究了对氯酚在多壁碳纳米管修饰玻碳电极（MWNTs/GC）上的电化学行为。MWNTs/GC电极对对氯酚具有良好的电催化作用,相比玻碳电极对氯酚的氧化峰电位负移76 mV,峰电流达到玻碳电极上的8倍。通过线性扫描伏安法研究了富集时间、溶液pH和扫描速率对对氯酚氧化的影响。并采用计时电流法研究了氧化峰电流与对氯酚的浓度关系,结果显示峰电流与对氯酚的浓度在2.0×10^-7-2.0×10^-4mol/L范围内呈良好线性关系,检出限为8.8×10-8mol/L（S/N=3）。放置7 d后,对氯酚在碳纳米管上的峰电流仍能达到最初电流的96.2%,表明电极的稳定性较好。     

对硝基苯酚在多壁碳纳米管修饰玻碳电极上的电化学行为及分析测定

水中对硝基苯酚主要来源于化工、制药行业,它有致癌作用。人们已对它的测定方法进行了大量的研究,最早采用的测定方法是分光光度法,其检测限偏高;色谱法测定对硝基苯酚,操作繁琐,仪器昂贵,分析成本高。后来又发展了一种操作更方便的直接用于测定的电化学方法。本文旨在利用碳纳米管对对硝基苯酚的吸附性能,研究对硝基苯酚在多壁碳纳米管修饰电极上的电化学行为。     

A novel poly(cyanocobalamin) modified glassy carbon electrode as electrochemical sensor for voltammetric determination of peroxynitrite

This report described the direct voltammetric detection of peroxynitrite (ONOO⁻) at a novel cyanocobalamin modified glassy carbon electrode prepared by electropolymeriation method. The electrochemical behaviors of peroxynitrite at the modified electrode were studied by cyclic voltammetry. The results showed that this new electrochemical sensor exhibited an excellent electrocatalytic activity to oxidation of peroxynitrite. The mechanism of catalysis was discussed. Based on electrocatalytic oxidation of peroxynitrite at the poly(cyanocobalamin) modified electrode, peroxynitrite was sensitively detected by differential pulse voltammetry. Under optimum conditions, the anodic peak current was linear to concentration of peroxynitrite in the range of 2.0 × 10⁻⁶ to 3.0 × 10⁻⁴ mol L⁻¹ with a detection limit of 1.0 × 10⁻⁷ mol L⁻¹ (S/N of 3). The proposed method has been applied to determination of peroxynitrite in human serum with satisfactory results. This poly(cyanocobalamin) modified electrode showed high selectivity and sensitivity to peroxynitrite determination, which could be used in quantitative detection of peroxynitrite in vivo and in vitro.     

Sensitive electrochemical determination of Sudan II in food samples using a poly(aminosulfonic acid) modified glassy carbon electrode

In this paper, a novel poly(aminosulfonic acid) modified glassy carbon electrode (PASA/GCE) for the determination of Sudan II was fabricated through electrochemical polymerizat ion. The electrochemical behavior of Sudan II at the modified electrode was studied by cyclic voltammetry. Results show that the modified electrode exhibits excellent electrocatalytic activity toward the electrochemical redox reaction of Sudan II. Under optimal experimental conditions, the oxidation peak current is linearly proportional to the concentration of Sudan II in the ranges of 4.0 × 10^?8 to 1.0 × 10^?6 mol L^?1 and 1.0 × 10^?6 to 1.2 × 10^?5 mol L^?1. The linear regression equations are i _pa(A) = 2.87c + 3.74 × 10^?6, r = 0.9977 and i _pa(A) = 0.78c + 6.11 × 10^?6, r = 0.9982, respectively, and the detection limit is 4.0 × 10^?9 mol L^?1. The novel method shows good recovery, reproducibility and sensitivity for the voltammetric determination of Sudan II in food samples.     

Electrochemical behavior and determination of clozapine on a glassy carbon electrode modified by electrochemical oxidation.

The adsorptive and electrochemical behaviors of clozapine (CLZ) were investigated on a glassy carbon electrode that was electrochemically treated by anodic oxidation at +1.8 V, following potential cycling in the potential range from -0.8 to 1.0 V vs. Ag/AgCl reference electrode. Based on the obtained electrochemical results, an electrochemical-chemical (EC) mechanism was proposed to explain the electrochemical oxidation of CLZ. The resulting electrochemically pretreated glassy carbon electrode (EPGCE) showed good activity to improve the electrochemical response of the drug. CLZ was accumulated in a phosphate buffer (pH 6) at a certain time, and then determined by differential pulse voltammetry. The anodic and cathodic peak currents showed a linear function in the concentration ranges of 0.1 - 1, 1 - 10 and 10 - 100 microM with various accumulation times. The proposed method was successfully used for the determination of CLZ in pharmaceutical preparations. The preconcentration medium-exchange approach was utilized for the selective determination of the drug in spiked urine samples with satisfactory results. The recovery levels of the method reached 96% (RSD, 1.8%) and 90% (RSD, 2.8%) for urine and plasma samples, respectively.     

Simultaneous determination of N-acetyl-p-aminophenol and p-aminophenol with poly(3,4-ethylenedioxythiophene) modified glassy carbon electrode

A sensitive and selective method was developed for the determination of N-acetyl-p-aminophenol (APAP) and p-aminophenol (PAP) using poly(3,4-ethylenedioxythiophene) (PEDOT)-modified glassy carbon electrode (GCE). Cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical reaction of APAP and PAP at the modified electrode. Both APAP and PAP showed quasireversible redox reactions with formal potentials of 367 mV and 101 mV (vs. Ag/AgCl), respectively, in phosphate buffer solution of pH 7.0. The significant peak potential difference (266 mV) between APAP and PAP enabled the simultaneous determination both species based on differential pulse voltammetry. The voltammetric responses gave linear ranges of 1.0 × 10⁻⁶-1.0 × 10⁻⁴ mol L⁻¹ and 4.0 × 10⁻⁶-3.2 × 10⁻⁴ mol L⁻¹, with detection limits of 4.0 × 10⁻⁷ mol L⁻¹ and 1.2 × 10⁻⁶ mol L⁻¹ for APAP and PAP, respectively. The method was successfully applied for the determination of APAP and PAP in pharmaceutical formulations and biological samples.     

苦参碱在多壁碳纳米管修饰玻碳电极上的电催化氧化及其电分析方法

研究了苦参碱(Matrine, MT) 在多壁碳纳米管修饰玻碳电极(MWCNT/GCE)上的电化学行为. 与GCE相比, MT在MWCNT/GCE上峰电位负移120 mV, 峰电流增大约2.5倍, 表明MWCNT/GCE对MT的电化学氧化具有良好的催化作用. 同时测定并计算了MT在MWCNT/GCE上的电极过程动力学参数: 电子转移系数α、电极反应速率常数ks、扩散系数D. 运用差分脉冲伏安法对苦参碱样品含量进行测定, 相对标准偏差为0.12%～2.9%, 加标回收率为98.4%～99.0%. 该方法可用于MT的电化学定量测定.     

Electrochemical determination of dopamine using a poly(2-picolinic acid) modified glassy carbon electrode

A poly(2-picolinic acid) chemically modified electrode (CME) for the determination of dopamine (DA) by cyclic voltammetry is described. Compared with a bare glassy carbon electrode, the CME exhibits a 200 mV shift of the oxidation potential of DA in the cathodic direction and a marked enhancement of the current response. In pH 7.0 buffer solution, a linear calibration graph is obtained over the range from 2.5 x 10(-7) to 1.0 x 10(-5) mol dm-3 with a correlation coefficient of 0.998. The detection limit is 3.0 x 10(-8) mol dm-3. The modified electrode eliminated efficiently the interference from ascorbic acid (AA) when present in a 150-fold concentration ratio. It also showed excellent stability and reproducibility.     

Voltammetric determination of bisoprolol on a glassy carbon electrode modified by poly(arylene phthalide)

New voltammetric sensors based on glassy carbon electrodes (GCEs) modified by poly(arylene phthalide) are studied. The electrochemical behavior of bisoprolol on GCEs modified by poly(arylene phthalide) is investigated. The effects of potential scan rate, time of accumulation on the electrode, pH of supporting electrolyte, and concentration on the current of bisoprolol electrooxidation are estimated. A procedure is developed for the voltammetric determination of bisoprolol on glassy carbon electrodes modified by poly(arylene phthalide). The dependence of the analytical signal on the concentration of bisoprolol is linear in the range 10^–6–10^–5 M with the limit of detection (3.4–9.8) × 10^–8 M.     

Sensitive determination of phenylephrine and chlorprothixene at poly(4-aminobenzene sulfonic acid) modified glassy carbon electrode

Phenylephrine (i.e. PHE) and chlorprothixene (i.e. CPT), two effective and important antipsychotic drugs with low redox activity, were found generating an irreversible anodic peak at about +0.89 V (vs. SCE) and +1.04 V in 0.05 M HAc–NaAc (pH 5.0) or NH₂CH₂COOH–HCl (pH 2.4) buffer solution at poly(4-aminobenzene sulfonic acid) modified glassy carbon electrode (i.e. poly(4-ABSA)/GC), respectively. Sensitive and quantitative measurement for them based on the anodic peaks was established under the optimum conditions. The anodic peak current was linear to PHE and CPT concentrations from 1 × 10⁻⁷ to 1.5 × 10⁻⁵ M and 2 × 10⁻⁶ to 4.5 × 10⁻⁵ M, the detection limits obtained were 1 × 10⁻⁸ and 1 × 10⁻⁷ M, separately. The modified electrode exhibited some excellent characteristics including easy regeneration, high stability, good reproducibility and selectivity. The method proposed was successfully applied to the determination of PHE and CPT in drug injections or tablets and proved to be reliable compared with ultraviolet spectrophotometry. The modified electrode was characterized by electrochemical methods.     

聚精氨酸修饰玻碳电极上多巴胺的电化学特性及其检测

用循环伏安法制备了聚精氨酸修饰玻碳电极,研究了神经递质多巴胺在该聚合物薄膜修饰电极上的电化学行为及其检测。在pH7.0的磷酸盐缓冲溶液中,多巴胺在聚精氨酸修饰电极上于0.19V和0.16V处出现一对灵敏、可逆的氧化还原峰。在最佳测试条件下,氧化峰电流与多巴胺的浓度在3.0×10-7~8.0×10-4mol/L范围内呈良好的线性关系,线性回归方程为Ipa(μA)=86.063C(mmol/L) 20.183,相关系数r=0.9993,最低检测限(3σ)5.0×10-8mol/L。用于多巴胺针剂含量的测定,结果满意。     

芦丁在纳米金修饰玻碳电极上的电化学行为及其测定

采用循环伏安法将纳米金电沉积于玻碳电极表面,制备了纳米金修饰玻碳电极(NG/GCE).在pH3.29的Britton-Robinson(B-R)缓冲溶液中,用循环伏安法研究了芦丁在NG/GCE上的电化学行为.结果表明,NG/GCE对芦丁的氧化还原反应有良好的电催化作用.用方波伏安法测得芦丁的还原峰电流与其浓度在2.0×10-8～2.0×10-6mol/L范围内呈线性关系,检出限为1.0×10-8mol/L(S/N=3).     

Study on electrochemical behavior of tryptophan at a glassy carbon electrode modified with multi-walled carbon nanotubes embedded cerium hexacyanoferrate

Electrochemical behavior of cerium hexacyanoferrate (CeHCF) incorporated on multi-walled carbon nanotubes (MWNTs) modified GC electrode is investigated by scanning electron microscopy (SEM) and electrochemical techniques. The CeHCF/MWNT/GC electrode showed potent electrocatalytic activity toward the electrochemical oxidation of tryptophan in phosphate buffer solution (pH 7.0) with a diminution of the overpotential of 240 mV. The anodic peak currents increased linearly with the concentration of tryptophan in the range of 2.0 × 10⁻⁷ to 1.0 × 10⁻⁴ M with a detection limit of 2.0 × 10⁻⁸ M (at a S/N = 3). And the determination of tryptophan in pharmaceutical samples was satisfactory.     

Voltammetric determination of levofloxacin using a glassy carbon electrode modified with poly(o-aminophenol) and graphene quantum dots

A strategy was developed for the voltammetric determination of the antibiotic drug levofloxacin (LV) based on a glassy carbon electrode modified with a composite consisting of poly(o-aminophenol) and graphene quantum dots (PoAP/GQD) that was fabricated by electropolymerization. The PoAP/GQD composite provides a large surface area and sensing interface and strongly promotes the oxidation current of LV. Under optimal conditions, the modified GCE displays an oxidation peak current (best measured at a working voltage of 1.05 V vs. SCE) that is linearly related to the levofloxacin concentration in the range from 0.05 to 100 μM, and the detection limit is 10 nM (at an S/N of 3). The method was applied to the determination of levofloxacin in spiked milk samples where is gave recoveries between 96.0 and 101.0 %.

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Graphical Abstract We describe a one-step electrochemical polymerization method to synthesize a layer of conductive film of poly(o-aminophenol) and graphene quantum dots (PoAP/GQD) onto a glassy carbon electrode (GCE) surface. The composite film exhibited high electro catalytic activity for the quantitative determination of levofloxacin by stripping voltammetry.

     

Adsorptive stripping voltammetric determination of azithromycin at a glassy carbon electrode modified by electrochemical oxidation.

The adsorptive and electrochemical behaviors of azithromycin were investigated on a glassy carbon electrode that was electrochemically treated by anodic oxidation at +1.8 V, following potential cycling in the potential range from -0.8 to +1.0 V. The resulting electrode showed good activity to improve the electrochemical response of the drug. An adsorptive stripping voltammetric method for the determination of azithromycin at an electrochemically activated glassy carbon electrode has been developed. Azithromycin was accumulated in phosphate buffer, pH 6, at a potential of +0.3 V (vs. Ag/AgCl electrode) for a certain time, and then determined by differential pulse voltammetry. The oxidative peak current at +0.82 V, at a scan rate of 20 mV s(-1), was a linear function of the concentration in the ranges of 0.25 - 2 microg mL(-1) and 1 - 10 microg mL(-1) using a 240 or 60 s(-1) preconcentration time, respectively. Application of the method to the determination of azithromycin in pharmaceuticals resulted in an acceptable deviation from the stated concentration. The preconcentration medium-exchange approach was utilized for the selective determination of the drug in spiked urine samples with satisfactory results. The peak current was linear with the drug concentration in the range of 0.5 - 3.5 microg per mL urine. The detection limit was 0.2 microg mL(-1) urine. The recovery levels of the method reached 96.3%.