Design of a New Carbon Paste Electrode Modified with TiO2 Nanoparticles to Use in an Electrochemical Study of Codeine and Simultaneous Determination of Codeine and Acetaminophen in Human Plasma Serum Samples

A new electrochemical sensor was fabricated via TiO₂ nanoparticles onto a carbon paste electrode. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) studied the response of the modified electrode toward codeine. The effects of pH, modifier amount, pulse amplitude, and scan rate of potential have been examined. Using DPV, we could measure simultaneously codeine and acetaminophen in one mixture. The detection limits of 0.018 and 0.050 µmol L^?1 were achieved for codeine and acetaminophen, respectively. The electrooxidation pathway, transfer coefficient, and standard rate constant, are estimated. The proposed voltammetric sensor was successfully applied to determination of codeine and acetaminophen in human plasma serum samples.     

辣根过氧化物酶在碳纳米管-离子液体修饰碳糊电极上的直接电化学研究

以室温离子液体1-丁基-3-甲基咪唑六氟磷酸盐（［EMIM］PF6）为粘合剂与多壁碳纳米管（Multi-walled carbon nanotubes,MWCNTs）、石墨粉相混合制备新型碳糊电极,并在该电极表面修饰辣根过氧化物酶（HRP）制成新型碳糊酶电极（HRP-MWCNTs-CILE）。应用循环伏安法（CV）和计时电流法（it）研究了该修饰电极的直接电化学行为。结果表明,该修饰电极在pH 6.0的0.05 mol/L磷酸缓冲溶液中,其循环伏安曲线上出现了1对准可逆的氧化还原峰,为HRP中Fe（Ⅲ）/Fe（Ⅱ）电对的特征峰。该修饰电极对过氧化氢具有良好的催化活性、抗干扰能力和稳定性。在最佳条件下,修饰电极对H2O2的测定线性范围为7.0×10-6~3.0×10-3 mol/L,检出限（S/N=3）为2.5×10-6 mol/L。该传感器具有制备简单、成本低廉、响应快等特点,具有较好的应用前景。     

Influence of Surface-Active Compounds on Starch Dispersion in Water. Part I. Starch Pasting

The influence of native lipids and additives of surface-active compounds on starch paste rheology was investigated. The aim of the study was to gain better understanding of mechanisms involved in starch gelatinization and how these structure changes of granules later affect rheological properties of pastes and gels. Starches from three main sources—potato, maize, and wheat—were tested; sodium dodecylsulfate, oleate, and benzalkonium chloride were employed as additives. Starch pasting was examined by a rheometer to get a viscosity profile, also pastes were analyzed by differential scanning calorimetry, for particle size using a light scattering technique. Results revealed that there was a competition between native lipids and added surfactants for amylose complexation. Complexes formed during gelatinization were strongly affecting granule swelling and dissolution of starch polymers, and viscosity of pastes was mainly dependent on the particle size of a disperse phase in the paste. Addition of strong ionic surfactants to cereal starches resulted in smaller granular remnants and, therefore, decreased viscosity, while the weak anionic surfactant promoted an increase in the particle size and paste viscosity for both cereal and tuber starches. The mechanism of the effect of surfactants on the particle size in pastes is discussed.     

聚中性红膜修饰碳糊电极的电化学研究及其对维生素K3的检测

在一定温度下,以K2S2O8作引发剂,分别采用化学引发-电聚合和电引发-电聚合的方法制备了聚中性红膜修饰碳糊电极(PNR/CPE)。运用循环伏安法(CV)对修饰电极进行表征,并通过扫描电子显微镜(SEM)对聚合膜的表面形貌进行观察分析,推断了成膜的可能机理,探讨了最佳聚合条件。研究了维生素K3在该修饰电极上的电化学行为,并用差分脉冲伏安法(DPV)对其含量进行了测定。研究结果表明:经过化学引发后,中性红单体自由基增多,提高了成膜效率,此电极在NH3-NH4Cl溶液中对维生素K3有更好的电催化作用,其还原峰电流与浓度在2.0×10-6~1.2×10-4 mol/L范围内呈现出良好的线性关系,检出限为2.0×10-7 mol/L,回收率为94.7%~108.0%。     

Electrochemical Morphine Sensor Based on Gold Nanoparticles Metalphthalocyanine Modified Carbon Paste Electrode

Composites of gold nanoparticles (Au) electrochemically deposited and different metal phthalocyanines (Co, Ni, Cu, and Fe) were chemically prepared. The composites were used as modifiers for carbon paste electrodes and were used for the determination of morphine in presence of ascorbic acid and uric acid. Central metal atoms of phthalocyanine moiety affected the rate of electron transfer. Thus, the electroactivity of different modifiers were evaluated towards morphine oxidation. Au‐CoPcM‐CPE possessed the highest rate for charge transfer rate in all studied pH electrolytes. Limit of detection was 5.48×10^?9 mol L^?1 in the range of 4.0×10^?7 to 9.0×10^?4 mol L^?1.     

Determination of Arsenic(III) at a Nanogold Modified Solid Carbon Paste Electrode

A selective and sensitive electroanalytical method was developed for arsenic determination based on a nanogold (AuNP) modified solid carbon paste working electrode (SCPE) modified in two steps (i) physisorption and (ii) additional electrodeposition of nanogold particles in the presence of iodide. Copper(II) interference was solved by covering the gold layer by a self assembled mono layer (SAM) of glutathione. Using DPASV a linear response of the signal was obtained as a function of As(III) in the concentration range 0.05–20 µM (4–1498 ppb) with a limit of detection of 0.01 µM (0.9 ppb). Sample stirring and degassing were not needed. Application to the determination of arsenic(III) and (V) in underground water samples from Burkina Faso was successfully achieved.     

BL-1型轮轨润滑成膜膏的研制及其综合性能考察

BL-1型轮轨润滑成膜膏是中国科学院兰州化学物理研究所为火车车轮轮缘与钢轨侧面研制的一种专用粘稠膏状润滑剂,系由润滑油脂、固体润滑剂、金属氧化物、稀土氟化物和增粘剂等配制而成,具有极高的承载能力、低的摩擦系数及良好的抗磨和抗冲击性能。其在半径约为300m的曲线钢轨上使用半年的结果表明,钢轨的平均磨损量是0.5mm,仅为机械油润滑时的1/4,材料消耗费仅为机械油的1/7,因而是一种实用价值很高的轮轨润滑剂。BL-1型轮轨润滑成膜膏的润滑效果比机械油的高两倍,可以明显地降低磨损,延长火车车轮和铁路钢轨的使用寿命,提高机车牵引动力的有效利用率。     

A Novel Modified Carbon Paste Electrode for Potentiometric Determination of Mercury(II) Ion

A new modified carbon paste electrode (CPE) based on a recently synthesized ligand of Ethyl‐2‐(benzoylamino)‐3‐(2‐hydroxy‐4‐methoxyphenyl)‐2‐propenoate (EBHMP) as a suitable carrier for Hg²⁺ ion was described. The electrode exhibit a super Nernstian slope of 48.5±1.0 mV per decade for Hg²⁺ ion over a wide concentration range from 3.0×10^?7–3.1×10^?2 M. The lower detection limits are 1.0×10^?7 M Hg²⁺. The electrode has a fast response time (ca. 5 s), a satisfactory reproducibility and relatively long life time. The proposed sensor shows a fairly good selectivity toward Hg²⁺ ion in comparison to other common cations. The potentiometric responses are independent of the pH of the test solution in the pH range 1.0–4.0. The proposed electrode was used as an indicator electrode in potentiometric titration of mercuric ion with standard solution of EDTA. The direct determination of mercury in spiked wastewater and an amalgam sample gave results that compare favorably with those obtained by the cold vapor atomic absorption spectrometric method.     

Cyclic voltammetric studies of the redox behavior of iron(III)-vitamin B6 complex at carbon paste electrode

Electrochemical redox behavior of Fe-vit B₆ complex is investigated in HEPES buffer in the pH range 5.1–13.1 using cyclic voltammetry. Well-defined anodic and cathodic peaks are observed in the voltammograms at pH 13.1. At pH 8.0, only one cathodic peak and at pH 5.1, only one anodic peak are found. At all the pH values, the peak potential separation is much higher than that of a reversible electrochemical reaction. The peak current ratio (i _pa/i _pc) is less than unity and decreases with the scan rate. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 6, pp. 691–697. The text was submitted by the authors in English.