沙棘口服液中5-羟色胺的电化学检测

采用电化学沉积法制备咖啡酸膜修饰电极,研究了5-羟色胺(5-HT)在该修饰电极上的电化学行为。结果表明,高浓度的抗坏血酸(AA)和肾上腺素(EP)共存不干扰5-HT的检测,5-HT在0.41 V和-0.12 V出现一对灵敏的氧化还原峰,其氧化峰电流与浓度在2.0×10-6～6.0×10-5mol/L范围内呈良好的线性关系,检测下限为8.0×10-7mol/L。该修饰电极制备简单,可准确检测神兴沙棘欣之安口服液中5-HT的含量。     

毛细管电泳法测定沙棘药物制品心达康片中的山奈酚和槲皮素

建立了毛细管电泳法测定沙棘药物制品心达康片中山奈酚和槲皮素的方法,研究了缓冲溶液pH和浓度、分离电压和进样时间对分离的影响,通过分析实际样品并做加入回收实验验证了方法的可行性。     

Electrochemical determination of rusted steel surface stability

The stability of a rusted steel surface exposed to a 0.11 M sodium sulphate solution has been studied. Electrochemical impedance spectroscopy, polarization resistance and atomic absorption analysis techniques were used in conjunction with mild steel specimens rusted in a rural atmosphere and treated with different concentrations of phosphoric acid. Since most of the impedance diagrams obtained differ from the typical semicircle, it is not clear how to obtain kinetic information on the corrosion process. The polarization resistance technique gives more useful data.     

Electrochemical determination of elemental sulfur in Brazilian naphtha: method and validation

Sulfur compounds in petroleum have caused several problems such as corrosion of equipment, lack of high quality final products, and emission of toxic gases into the environment. Elemental sulfur can increase these problems, since small amounts of it turn mercaptans into potential corrosion agents. This paper describes the applicability of a voltammetric method to quantify elemental sulfur in Brazilian naphtha samples. Elemental sulfur was quantified in synthetic and real samples using square wave voltammetry and a hanging mercury drop electrode. The method was found to have low limits of detection (0.003 mg L⁻¹) and quantification (0.009 mg L⁻¹) and a good recovery range (94.0–108.6%). This voltammetric method has potential for use in elemental sulfur determination in naphtha samples containing mercaptans and aliphatic and aromatic disulfides.     

对乙酰氨基酚在硼掺杂金刚石薄膜电极上的电化学行为及测定

硼掺杂金刚石(BDD)薄膜电极是用于电化学分析的理想电极材料。采用循环伏安法研究了BDD电极上对乙酰氨基酚的电化学行为。研究发现,对乙酰氨基酚的氧化反应为不可逆电氧化反应,氧化峰电流与扫描速率的平方根成正比,受扩散控制。通过优化循环伏安测试参数建立了BDD电极上对乙酰氨基酚的测定方法,优化后测试参数为扫描速率10 mV/s,电压扫描范围为-1.0².0 V(vs.Ag/AgCl),扫描1次,扫描步长2.44 mV,得到氧化峰电流值与对乙酰氨基酚浓度在10.02.0 V(vs.Ag/AgCl),扫描1次,扫描步长2.44 mV,得到氧化峰电流值与对乙酰氨基酚浓度在10.0⁵00.0 mg/L范围内呈线性关系,线性回归曲线为Y=1.279 34×10500.0 mg/L范围内呈线性关系,线性回归曲线为Y=1.279 34×10⁶X+5.696 73,r=0.999 79。对本测定方法进行了精密度、稳定性和回收率的方法学考察,测定结果令人满意。     

对乙酰氨基酚在硼掺杂金刚石薄膜电极上的电化学行为及测定

硼掺杂金刚石(BDD)薄膜电极是用于电化学分析的理想电极材料。采用循环伏安法研究了BDD电极上对乙酰氨基酚的电化学行为。研究发现,对乙酰氨基酚的氧化反应为不可逆电氧化反应,氧化峰电流与扫描速率的平方根成正比,受扩散控制。通过优化循环伏安测试参数建立了BDD电极上对乙酰氨基酚的测定方法,优化后测试参数为扫描速率10 mV/s,电压扫描范围为-1.0~2.0 V(vs.Ag/AgCl),扫描1次,扫描步长2.44 mV,得到氧化峰电流值与对乙酰氨基酚浓度在10.0~500.0 mg/L范围内呈线性关系,线性回归曲线为Y=1.279 34×10~6X+5.696 73,r=0.999 79。对本测定方法进行了精密度、稳定性和回收率的方法学考察,测定结果令人满意。     

Electrochemical determination of plant-derived leuco-indigo after chemical reduction by glucose

Electrochemical determination of redox active dye species is demonstrated in indigo samples contaminated with high levels of organic and inorganic impurities. The use of a hydrodynamic electrode system based on a vibrating probe (250 Hz, 200 μm lateral amplitude) allows time-independent diffusion controlled signals to be enhanced and reliable concentration data to be obtained under steady state conditions at relatively fast scan rates up to 4 V s⁻¹. In this work the indigo content of a complex plant-derived indigo sample (dye content typically 30%) is determined after indigo is reduced by addition of glucose in aqueous 0.2 M NaOH. The soluble leuco-indigo is measured by its oxidation response at a vibrating electrode. The vibrating electrode, which consisted of a laterally vibrating 500 μm diameter gold disc, is calibrated with Fe(CN)₆ ^3−/4− in 0.1 M KCl and employed for indigo determination at 55, 65, and 75 °C in 0.2 M NaOH. Determinations of the indigo content of 25 different samples of plant-derived indigo are compared with those obtained by conventional spectrophotometry. This comparison suggests a significant improvement by the electrochemical method, which appears to be less sensitive to impurities.     

Electrochemical method for quantitative determination of trace amounts of disperse dye in wastewater

The electrochemical behaviour of Disperse Red 13 dye at a glassy carbon electrode was investigated in both organic and aqueous organic mixtures. Best results were obtained in N,N‐dimethylformamide/Britton–Robinson buffer (1:1, v/v), which displays a well‐defined peak at ‐0.40 V (vs Ag/AgCl) owing to reduction of the protonated nitro group. This method can be successfully applied to the electroanalytical determination of Disperse Red 13 in a very simple and inexpensive way. All the differential pulse voltammetry parameters were optimised by using a glassy carbon electrode modified with poly(glutamic acid) films. The targeted analytical method presented a linear response from Disperse Red 13 concentrations between 2.5 × 10^?7 and 3 × 10^?6 mol l^?1 (r = 0.997), with a detection limit of 1.5 × 10^?8 mol l^?1 and recoveries of 89.7–95.10% in water samples. Disperse Red 13 was successfully determined in textile industry wastewater by means of the proposed method after pre‐extraction in a solid‐phase extraction cartridge.     

Electrochemical determination of adrenaline in human urine using a boron-doped diamond film electrode

A simple and sensitive square-wave voltammetric method for the determination of adrenaline on unmodified boron-doped diamond film electrode was developed. Adrenaline exhibited the quasi-reversible behavior with oxidation peak on the forward scan at + 0.75 V and smaller reduction peak on the reverse scan at − 0.10 V vs. Ag/AgCl electrode in 0.5 M HClO₄. The effect of supporting electrolyte, pH and scan rate on the current response of adrenaline was examined to select the optimum experimental conditions. At optimized square-wave voltammetric parameters (amplitude of 100 mV, frequency of 50 Hz and step potential of 5 mV), the linear concentration range from 0.7 to 60 μM (R² = 0.998, number of measurements n = 6), the excellent repeatability (relative standard deviation of 3.5% for n = 50) and the detection limit of 0.21 μM were achieved without any chemical modification and pretreatment of working electrode. The practical application of method was demonstrated in the determination of adrenaline in spiked human urine samples with satisfactory recoveries (98 to 102%).     

Electrochemical determination of bromide at a multiwall carbon nanotubes-chitosan modified electrode

A multiwall carbon nanotubes (MWNTs)-chitosan modified glassy carbon electrode (GCE) exhibits attractive ability for highly sensitive cathodic stripping voltammetric measurements of bromide (Br⁻). In pH 1.8 H₂SO₄ solution, a substantial increase in the stripping peak current of Br⁻ (compared to bare GCE and chitosan modified GCE) is observed using MWNTs-chitosan modified electrode. Operational parameters were optimized and the electrochemical behaviors of Br⁻ were studied by different electrochemical methods. The kinetics parameters were measured, the number of electron transfer (n) was 1 and the transfer coefficient (α) is 0.17. A wide linear calibration range (3.6 × 10⁻⁷-1.4 × 10⁻⁵ g mL⁻¹) was achieved, with a detection limit of 9.6 × 10⁻⁸ g mL⁻¹. The mechanism of electrode reaction was fully discussed.     

Electrochemical Study on TAGN. A differential pulse polarography determination

This work shows an electrochemical study about triaminoguanidine nitrate, estimating the influence of the reaction compounds for the formation of TAGN and secundary compounds and hydrolysis products of this formation reaction. The conditions to determine polarographically the content of TAGN in a propellant without the interference of those compounds are verified. The method used is the differential pulse polarography in aqueous medium, due to the high solubility of TAGN in water. We have used three different media as electrolyte support, verifying the influence of different variables, as pH, drop time etc., to obtain the optimum work conditions.     

五味子药材中醇甲和酯甲的测定

五味子以100%甲醇溶解,用超声波清洗器提取20 min,建立一种同时对五味子药材中五味子醇甲和酯甲定性和含量测定的HPLC-MS方法。色谱条件:色谱柱ZORBAXEclipse XDB-C18(150 mm×4.6 mm i.d.,5μm),流动相甲醇-水(体积比65∶35),流速0.8 mL/min,检测波长220 nm,柱温20℃,进样量20μL。质谱条件:电喷雾离子源(ESI+源),扫描范围(m/z):300~600,干燥气温度350℃,干燥气流速8.0 mL/min,雾化气压力275.8 kPa。结果表明,五味子醇甲和酯甲分别在1.3~83.2μg和1.04~66.56μg浓度范围内具有良好的线性关系,相关系数r分别为0.998和0.997,平均加标回收率分别为100.7%和99.7%,RSD均小于2%。本方法灵敏度高、操作简便、结果准确,可用于五味子中五味子醇甲和酯甲定性及定量的测定。     

聚对苯二酚修饰电极测定多巴胺和L-色氨酸的电化学研究

制备了对苯二酚聚合膜修饰玻碳电极(PHQ/GCE),研究了多巴胺(DA)和L-色氨酸(L-Trp)在该电极上的电化学行为,以及支持电解质、溶液pH、扫描速率等对DA和L-Trp伏安响应的影响.实验发现,在pH 5.5的NaH2PO4-Na2HPO4缓冲溶液中,可用PHQ/GCE测定溶液中的DA和L-Trp,两者氧化峰电流均与浓度在1×10-3～5×10-6 mol/L范围内呈良好线性关系,相关系数分别为0.998 3和0.996 5,检出限分别为1×10-6 mol/L和5×10-7 mol/L,该方法简便快捷.     

Electrochemical simultaneous determination of nitrophenol isomers at nano-gold modified glassy carbon electrode

A novel method for simultaneous determination of nitrophenol isomers at nano-gold modified glassy carbon electrode has been developed. The gold nanoparticles were directly electrodeposited onto the glassy carbon electrode via a constant potential −0.2 V (vs. SCE) for 60 s from 0.1 mol L⁻¹ KNO₃ containing 0.4 g L⁻¹ HAuCl₄. The resulting electrode (nano-Au/GCE) was characterized with scanning electron microscopy (SEM). The electrochemistry response of nitrophenol isomers at the nano-Au/GCE was studied. The result indicated that o-, m-, and p- nitrophenol are separated entirely at nano-Au/GCE, and a semi-derivative voltammetric technology was adopted to enhance the determination sensitivity. This modified electrode could be applied to direct simultaneous voltammetric determination of nitrophenol isomers in water samples without preseparation with higher sensitivity.     

Electrochemical determination of anticancer drug fulvestrant at dsDNA modified pencil graphite electrode

The interaction of fulvestrant with double-stranded DNA (dsDNA) was studied by means of differential pulse voltammetry (DPV) at dsDNA modified pencil graphite electrode (PGE). The decrease in intensity of the guanine oxidation signals was used as an indicator for the interaction mechanism and sensitive determination of fulvestrant in pH 4.80 acetate buffer (30% ethanol). A linear dependence of the guanine oxidation signals was observed within the range of 1.00–20.00 μg/mL fulvestrant, with a detection limit of 0.41 μg/mL. The determination method was validated according to the standard validation procedure. The proposed method was applied to fulvestrant pharmaceutical dosage form.     

Electrochemical determination of estradiol using a poly(l-serine) film-modified electrode

A thin film of poly(l-serine) was prepared via electropolymerization for the determination of trace levels of estradiol. In pH 5.0 phosphate buffer, l-serine was oxidized during the cyclic potential sweeps between −0.60 and 2.0 V, forming a thin film at the electrode surface. The electrochemical behavior of estradiol was investigated. The oxidation peak potential of estradiol shifts negatively at the poly(l-serine) film-coated glassy carbon electrode (GCE) compared with that at the bare GCE. Otherwise, the oxidation peak current greatly increases at the poly(l-serine) film-modified GCE. These phenomena suggest that the poly(l-serine) film exhibits catalytic activity towards the electrochemical oxidation of estradiol. Based on this, a sensitive, rapid and simple electrochemical method was proposed for the determination of estradiol. The limit of detection is evaluated to be 2.0 × 10⁻⁸ mol L⁻¹. Finally, this method was successfully used to determine estradiol in blood serum.     

高效液相色谱法测定槐角中染料木素的含量

采用高效液相色谱法测定槐角中游离染料木素和总染料木素含量,为评价槐角的品质提供了科学的依据。采用Diamonsil C18柱(250 mm×4.6 mm,5μm),流动相为甲醇-水(60∶40),流速1.0 mL/min,检测器波长260 nm,柱温为30℃,加标回收率为90.6%～101.2%,RSD为3.89%和4.23%,2个槐角样品的总染料木素含量分别为4.65%和4.37%。该方法操作简便,准确可靠。     

Electrochemical determination of the standard Gibbs free energy change of the graphite-Oxygen reactions

A calcia doped zirconia solid oxide electrolyte galvanic cell was investigated in the temperature range of 700–950°C to directly and more accurately measure the standard Gibbs free energy change of the following reactions: $\text{CO(g) +}\text{1}\text{2}\text{O}{}_2\text{(g) = CO}{}_2\text{(g)}$C_(graphite) + CO₂(g) = 2 CO(g). The results obtained in the present investigation are well within the scatter band of the calorimetric and spectroscopic data.     

Electrochemical transient techniques for determination of uranium and rare-earth metal separation coefficients in molten salts

The main step in the pyrometallurgical recycling process of spent nuclear fuel is a molten salt electrorefining. The knowledge of separation coefficients of actinides (U, Np, Pu and Am) and rare-earth metals (Y, La, Ce, Nd and Gd) is very important for this step. Usually the separation coefficients are evaluated from the formal standard potentials of metals in melts containing their own ions, i.e. values obtained by potentiometric method. Electrochemical experiments were carried out at 723-823 K in order to estimate separation coefficients in LiCl-KCl eutectic melt containing uranium and lanthanum trichlorides. The electrochemical behaviour of UCl₃ in LiCl-KCl melt was studied by different electrochemical methods. The diffusion coefficients of U(III) were determined by linear sweep voltammetry, chronopotentiometry and chronoamperometry. The standard rate constants of charge transfer for electroreduction of uranium, U(III) + 3e⁻ → U, were calculated by the impedance spectroscopy method. The values of constants testify that electroreduction of U(III) to U is mainly controlled by the rate of charge transfer. La(III) discharge on uranium electrode was also investigated. It was shown that for the calculation of uranium and lanthanum separation coefficients it is necessary to determine the voltammetric peak potentials of U(III) and La(III), their concentration in the melt and the kinetic parameters relating to U(III) discharge such as transfer and diffusion coefficients, and standard rate constants of charge transfer.     

Electrochemical properties and simultaneous determination of dihydroxybenzene isomers at ordered mesoporous carbon-modified electrode

The voltammetric behaviors of dihydroxybenzene isomers were studied at an ordered mesoporous carbon-modified glassy carbon (OMC/GC) electrode. Compared to the bare electrode, the electrocatalytic activity of the modified electrode toward dihydroxybenzenes is evidenced by the increase of the peak current and the decrease of the peak separation (ΔE _p) in 0.1 M pH 5.0 phosphate buffer solution (PBS). Furthermore, at the OMC/GC-modified electrode, the three isomers could be separated entirely. The oxidation peak potential difference between hydroquinone and catechol is 154 mV, whereas that difference between catechol, and resorcinol is 370 mV. In the amperometric detection, the peak currents of dihydroxybenzene increased linearly with increasing dihydroxybenzene contents. The detection limits were 7.6 × 10⁻⁸ M, 1.0 × 10⁻⁷ M, 9.0 × 10⁻⁸ M for hydroquinone, catechol and resorcinol, respectively, which are the lowest values ever reported for dihydroxybenzene isomers. These make OMC/GC electrode a promising candidate for the simultaneous determination of isomers.