Diffusion coefficient measurements in microfluidic devices

A glassy carbon electrode (GCE) modified with Pd/IrO(2) provides excellent electrocatalytic oxidation of hydrogen peroxide. Glucose oxidase (GOD) and xanthine oxidase (XOD) were co-immobilized on the modified electrode with a thin film Nafion coated on the enzyme layer to form a glucose (Glu)/hypoxanthine (Hx) sensor, without interference from electroactive species such as ascorbic acid (AA) and uric acid (UA). Its response was evaluated with respect to the enzyme amount on the electrode, pH and temperature of the electrolyte. The prepared bienzymic biosensor, used as the detector of HPLC gave a detection limit of 1.0x10(-6) mol l(-1) Glu and 2.0x10(-7) mol l(-1) Hx (Hx) with a linear concentration range of 5.0x10(-6)-2.5x10(-3) mol l(-1) and 1.0x10(-6)-5.0x10(-4) mol l(-1), respectively. Coupled with microdialysis, it was used to monitor the concentrations of Glu and Hx in rat brain.     

高效液相色谱-电化学检测法测定鼠脑微透析液中谷胱甘肽和半胱氨酸

采用高效液相色谱法,用电化学检测手段成功地测定了沙土鼠脑纹状体微透析液内的谷胱甘肽（ＧＳＨ）和半胱氨酸（Ｃｙｓ）。检测前用电化学自清洗方式能有效地提高玻璃碳电极的检测水平,使其具有较好的重现性和回收率。Ｃｙｓ和ＧＳＨ的回收率分别为９１．４％和８７．３％。电化学检测的工作电压为０．９Ｖ,用外标法定量。由微透析探针获取的纹状体透析液Ｃｙｓ和ＧＳＨ的浓度分别为６８．５９和６５．５４ｎｍｏｌ／Ｌ,验证了方法的实用性和可靠性。     

Spectrofluorimetric determination of thiols by use of N[P-(2-benzoxazolyl)phenyl]maleimide

The weak fluorescence of N-[P-(2-benzoxazolyl)phenyl]maleimide (BOPM) can be greatly enhanced by thiol-containing compounds. A sensitive and simple spectrofluorimetric method based on the use of BOPM has been developed for the determination of thiols such as cysteine (Cys) and reduced glutathione (GSH). Calibration plots were linear in the concentration range from 0 to 1.6 x 10(-7) mol L(-1) for Cys and 0 to 1.7 x 10(-7) mol L(-1) for GSH. The detection limits (3a) were 2.36 x 10(-10) mol L(-1) for Cys and 1.49 x 10(-10) mol L(-1) for GSH. Many other amino acids (present at 100-fold greater concentrations) did not interfere with the determination. The proposed method has been used for the determination of Cys in protein hydrolysate and cystine electrolyte or GSH in serum, with recoveries of 95.4-103.7%.     

Platinum particles-modified electrode for HPLC with pulsed amperometric detection of thiols in rat striatum

A new chemically modified electrode based on the immobilization of Pt particles is fabricated and exhibits electrocatalytic oxidation for L-cysteine (L-Cys), glutathione (GSH) and penicillamine (PEN) with relatively high sensitivity. It is also adaptable to HPLC for pulsed amperometric detection (PAD) of these thiols. PAD largely improves the detection sensitivity because the alternated polarizations can effectively clean and reactivate the electrode surface. It is shown that the peak currents of L-Cys, GSH and PEN are linear to their concentrations, with the calculated detection limit of 1.1 x 10(-7), 1.8 x 10(-7) and 3.8 x 10(-7) mol L(-1), respectively (S/N = 3). The method has been successfully applied to assess the contents of L-Cys and GSH in rat striatal microdialysates. The average contents of the two analytes in rat striatum are 2.6 x 10(-6) and 2.8 x 10(-6) mol L(-1), respectively.     

HPLC／CoPC修饰电极安培检测大鼠心肌线粒体中谷胱甘肽的研究

研究了钴酞菁修饰电极的修饰方法及其电化学性质。它可以催化氧化谷胱甘肽,降低ＧＳＨ的过电位。以ＣｏＰＣ何尝修饰电极为工作电极的安培薄层化学检测器,与高压认相色谱联用,在工作电极电位为＋０．８Ｖ时,ＧＳＨ的浓度在３．０＊１０＾－６ｍｏｌ／Ｌ－１．０＊１０＾－３ｍｏｌ／Ｌ浓度范围内与峰电流呈良好的线性关系,线性相关系数为０．９９９１,检出限为１．０＊１０＾－３ｍｏｌ／Ｌ浓度范围内与峰电流呈良好的线性关系     

Electrochemical Determination of Reduced Glutathione at Multiwalled Carbon Nanotubes/Poly(bromocresol green)Modified Glassy Carbon Electrode

A multiwalled carbon nanotubes/poly(bromocresol green) modfied glassy carbon electrode (MWNTs-PBG/GCE) was used to investigate the electrochemical behavior of reduced glutathione(GSH). GSH showed an irreversible oxidation process on MWNTs-PBG/GCE with an oxidation peak at 0.77 V(vs. SCE) in a phosphate buffer solution(pH=4.0). The kinetic parameters of the electrochemical behavior of GSH on MWNTs-PBG/GCE were calculated. Under the optimal conditions and with the help of amperometric method, a linear relationship was obtained between the oxidation peak current and GSH concentration in the range from 2×10–7 mol/L to 5×10–6 mol/L with the detection limit as 1×10–8 mol/L(signal-to-noise ratio of 3). The current reached the steady-state current within about 5 s. The modified electrode surface had very good reproducibility and stability.     

Electrochemical parameters of ethamsylate at multi-walled carbon nanotube modified glassy carbon electrodes

In this paper, some electrochemical parameters of ethamsylate at a multi-walled carbon nanotube modified glassy carbon electrode, such as the charge number, exchange current density, standard heterogeneous rate constant and diffusion coefficient, were measured by cyclic voltammetry, chronoamperometry and chronocoulometry. The modified electrode exhibits good promotion of the electrochemical reaction of ethamsylate and increases the standard heterogeneous rate constant of ethamsylate greatly. The differential pulse voltammetry responses of ethamsylate were linearly dependent on its concentrations in a range from 2.0 x 10(-6) to 6.0 x 10(-5) mol L(-1), with a detection limit of 4.0 x 10(-7) mol L(-1).     

以3,4-二羟基肉桂酸为介质的多壁碳纳米管糊电极用于检测药物和尿液样品中的谷胱甘肽(英文)

A sensitive and selective electrochemical sensor for the determination of glutathione(GSH) was developed using a modified multiwall carbon nanotube paste electrode with 3,4 dihydroxy cinnamic acid as a mediator.This modified electrode showed very high electrocatalytic activity for the anodic oxidation of GSH.Under the optimized conditions,the electrocatalytic peak current showed a linear relationship with GSH concentration in the range of 0.5-400.0 μmol/L with a detection limit of 0.1 μmol/L GSH.The relative standard deviations for seven successive assays of 5.0 and 25.0 μmol/L GSH were 2.2% and 2.7%,respectively.The modified electrode was used for the determination of GSH compounds in real urine samples.     

钯/聚苯胺纳米多层膜的制备及对抗坏血酸和多巴胺的催化氧化

采用脉冲电位法(PPSM)结合聚苯胺(PANI)的层层自组装制备了Pd/PANI交替沉积纳米多层膜, 并用于抗坏血酸(AA)和多巴胺(DA)的检测. 实验发现, 多层膜结构形貌及催化性能受前躯体K₂PdCl₆浓度、 脉冲条件及膜厚度等影响. 当K₂PdCl₆浓度为2×10^-3 mol/L, 阴极脉冲电位为-0.3 V, 阶跃次数为17时, 5层Pd/PANI修饰玻碳电极对AA和DA的催化性能最佳; 在0.1 mol/L磷酸盐缓冲液中, AA和DA的氧化峰明显分离[ΔE_p(AA, DA)=160 mV], 其峰电流与浓度分别在5×10^-5～4×10^-4和4×10^-5～1×10^-4 mol/L范围内呈较好线性关系, 实现了对AA和DA的同时测定. 该修饰电极具有良好的抗干扰性和稳定性.     

Electrochemical behavior of thiamine on a self-assembled gold electrode and its square-wave voltammetric determination in pharmaceutical preparations.

The electrochemical behavior of thiamine on a self-assembled electrode of L-cysteine (Cys/SAM/Au) has been investigated and Cys/SAM/Au can be used to detect thiamine using square-wave voltammetry (SWV). At pH 11.40 Britton-Robinson buffer, thiamine exhibits a well-defined anodic peak on Cys/SAM/Au. Under the optimized conditions, the anodic peak current of SWV was linear with the content of thiamine in the range of 1.1 x 10(-8) - 2.2 x 10(-6) mol/L; the detection limit was 5.5 x 10(-9) mol/L. The method was successfully applied to the determination of thiamine in pharmaceutical preparations.     

The enhanced electrogenerated chemiluminescence of Ru(bpy)3(2+) by glutathione on a glassy carbon electrode modified with some porphine compounds

It has been found that the electrochemical activity of glutathione was increased greatly at the glassy carbon electrodes modified with 5,10,15,20-tetraphenylporphine ruthenium(II) carbenyl (RuTPP), meso-tetraphenylporphine copper(II) complex (CuTTP) and hemin. It has been also found that glutathione would enhance the electrogenerated chemiluminescence (ECL) of Ru(bpy)3(2+) at a hemin glassy carbon electrode; the enhanced ECL intensity was linear with the concentration of glutathione in the range of 1 x 10(-7)-1 x 10(-4) mol l-1, based on which method for determination of glutathione has been developed. The detection limit of glutathione was 2 x 10(-8) mol l-1, and the relative standard deviation for 1 x 10(-6) mol l-1 glutathione was 2.7%. The mechanism for this ECL system has been proposed.     

葡萄糖在亚硝基五氰合铁酸铁修饰碳糊电极上的电化学行为研究

采用亚硝基五氰合铁酸铁(FePCNF)粉末与碳粉质量比为2∶3混合,制备了FePCNF修饰碳糊电极.研究了FePCNF修饰碳糊电极在KNO3溶液中的电化学行为和扫速、pH值及不同支持电解质的影响.该电极可用于催化氧化检测葡萄糖.实验表明:FePCNF修饰碳糊电极在0.5 mol/L KNO3溶液中有一对灵敏的氧化还原峰,峰电流与扫速呈线性关系.氧化峰电流与葡萄糖的浓度在2.0×10-6～2.4×10-5 mol/L之间有良好的线性关系(r=0.9934),检出限为6.3×10-7 mol/L.该电极具有良好的稳定性和重现性,适合于微量葡萄糖的检测.     

维生素B6在纳米金/石墨烯修饰电极上的电化学行为

将金纳米粒子电沉积在石墨烯修饰的玻碳电极表面,研究了维生素B6(VB6)在该修饰电极上的电化学行为。扫描电镜用于该修饰电极组装过程的形貌表征。实验结果表明:VB6在此修饰电极上出现一个良好的氧化峰,在最佳实验条件下,其氧化峰电流与VB6浓度在5.0×10-8～2.0×10-5 mol/L范围内呈线性关系,其线性回归方程为I(μA)=0.5697c(μmol/L)+0.06275,R=0.9992,检出限为2.0×10-8 mol/L(S/N=3)。一些常见的干扰物质如抗坏血酸不干扰VB6的检测。方法已用于片剂中VB6的含量的检测。     

多壁纳米管修饰电极电催化3,4-二羟基苯甲酸研究

应用循环伏安(CV)和方波伏安(SWV)法研究3,4-二羟基苯甲酸(DHBA)在多壁碳纳米管修饰的玻碳电极上的电化学行为.实验表明:该修饰电极对DHBA有较强的电催化作用.由方波伏安法测定的氧化峰电流在DHBA浓度为4.0×10-6~1.0×10-4mol/L和2.0×10-4~8.0×10-4mol/L范围内分段呈线性变化关系;相关系数各为0.9995和0.9992,检测限1.0×10-6mol/L.     

A nitric oxide biosensor based on horseradish peroxidase/kieselguhr co-modified pyrolytic graphite electrode

A reagentless nitric oxide (NO) biosensor was prepared using a pyrolytic graphite (PG) electrode modified with a composite film containing horseradish peroxidase (HRP) and kieselguhr. Noticeably, the electron-transfer reactivity of HRP was significantly enhanced when incorporated in the inorganic kieselguhr material. Consequently, we observed the direct electrochemical response of HRP in this composite film, which would be otherwise electrochemically silent (in the absence of kieselguhr). Importantly, this modified electrode demonstrated nice catalytic activity, as well as high stability, towards the reduction of NO. The peak current related to NO was linearly proportional to its concentration from 2.0 x 10(-7) to 2.0 x 10(-5) mol/L, and the relative standard deviation was 4 % for five successive determinations at a NO concentration of 1.0 x 10(-5) mol/L. The critical level in concentration was estimated to be (4.0 +/- 0.3) x 10(-8) mol/L.     

纳米金颗粒增强信号的电化学生物传感器用于谷胱甘肽和半胱氨酸的检测

构建了一种高灵敏检测谷胱甘肽(GSH)和半胱氨酸(Cys)的新型电化学生物传感器. 先将富含T碱基的DNA1和DNA2探针分别修饰在金电极和纳米金颗粒(AuNPs)上, 再加入Hg²⁺, 通过形成T-Hg²⁺-T结构使AuNPs结合到金电极表面. 当加入GSH(或Cys)后, GSH(或Cys)可以竞争结合T-Hg²⁺-T结构中的Hg²⁺, 使AuNPs离开电极表面. 由于AuNPs上修饰的DNA探针能够静电吸附大量电活性物质六氨合钌(RuHex), 因此该过程可引起计时电量信号的显著变化, 据此实现了GSH(或Cys)的高灵敏检测. 该传感器的检出限达10 pmol/L, 比荧光法或比色法降低了2~3个数量级. 实验结果表明, 该传感器具有较好的选择性.     

维生素B6在维生素B12修饰电极上的电化学行为及其分析应用

采用循环伏安法研究了维生素B6在维生素B12修饰玻碳电极上的电化学行为,建立了测定痕量维生素B6的新方法.在pH 8.6的NH3-NH4Cl缓冲溶液中,维生素B6在修饰电极上产生一个灵敏的氧化峰,采用差分脉冲伏安法测定,其氧化峰电流与维生素B6的浓度在8.0×10-7～2.0×10-4 mol/L范围内呈良好的线性关系,检出限为2.0×10-7 mol/L.该修饰电极具有良好的选择性、灵敏度及稳定性,用于片剂中维生素B6的定量分析,结果令人满意.     

A multi-wall carbon nanotubes-dicetyl phosphate electrode for the determination of hypoxanthine in fish.

An enzymeless sensor based on a multi-walled carbon nanotubes-dicetyl phosphate (MWCNT-DCP) film modified vitreous carbon electrode was developed for the determination of hypoxanthine. The MWCNT-DCP film modified electrode showed a remarkable enhancement effect on the oxidation peak current of hypoxanthine. Under the optimized conditions, the oxidation peak current is proportional to the concentration of hypoxanthine over the range from 5.0 x 10(-7) to 2.0 x 10(-4) mol L(-1) with a detection limit (S/N = 3) of 2.0 x 10(-7) mol L(-1). The MWCNT-DCP film modified electrode has been successfully used to detect hypoxanthine in fish samples.     

石墨烯/铁氰化钴复合膜修饰玻碳电极同时测定对苯二酚、邻苯二酚和间苯二酚

采用滴涂法和电沉积法制备了石墨烯/铁氰化钴复合膜修饰玻碳电极. 用扫描电镜对该纳米复合膜进行了表征.用循环伏安法研究了对苯二酚(HQ)、邻苯二酚(CT)和间苯二酚(RS)在修饰电极上的电化学行为. 实验结果表明, 相对于裸玻碳电极和石墨烯修饰电极, HQ, CT 和RS 在石墨烯/铁氰化钴修饰电极上的氧化峰电流显著提高. 利用差分脉冲伏安法测定, HQ, CT 和RS 分别在1.0×10^－6～1.5×10^－4 mol/L, 1.0×10^－6～2.0×10^－4 mol/L 和3.5×10^－6～2.5×10^－4 mol/L浓度范围内与氧化峰电流呈良好的线性关系, 相关系数分别为0.991, 0.993 和0.992. 信噪比为3 时, HQ, CT 和RS 检出限分别为2.0×10^－7, 2.1×10^－7 和3.5×10^－7 mol/L. 将该方法用于水样分析, 回收率为95.6%～106.1%.     

Sensitive voltammetric determination of tryptophan using an acetylene black paste electrode modified with a Schiff's base derivative of chitosan

Chitosan was modified by salicylaldehyde via Schiff's base reaction and the resulting product was modified on the surface of an acetylene black paste electrode (ABPE) by the drop-coating method. In 0.5 mol L(-1) acetate buffer (pH 4.2), a substantial increase in the anodic stripping peak current of tryptophan (Trp) (compared to conventional bare carbon paste electrode (CPE) and bare ABPE) is observed at the Schiff's base chitosan-modified electrode. The parameters influencing voltammetric determination of Trp have been optimized. Under the selected conditions, the linearity between the anodic peak currents and concentrations of Trp demonstrated a wide range of 6.0 × 10(-8) mol L(-1) to 2.0 × 10(-6) mol L(-1), 2.0 × 10(-6) mol L(-1) to 4.0 × 10(-5) mol L(-1) and 4.0 × 10(-5) mol L(-1) to 1.0 × 10(-4) mol L(-1), a low detection limit of 2.0 × 10(-9) mol L(-1) was obtained after a 60 s accumulation. In addition, the developed electrochemical sensor has been successfully applied for the determination of Trp in pharmaceutical and biological samples with satisfactory assay results.