槲皮素在氧化锆修饰玻碳电极上的伏安行为及检测

制备了氧化锆修饰的玻碳电极,采用示差脉冲伏安法和循环伏安法探究了槲皮素在该电极上的电化学行为。结果表明,制备的修饰电极在pH=7.00的磷酸盐缓冲溶液（PBS）中对槲皮素的氧化还原具有明显的电催化作用。采用槲皮素的氧化峰电流作为分析信号。在浓度为2.5×10-8~5×10-5 mol/L的范围内,氧化峰电流和浓度成良好的线性关系,线性方程为ip（μA）=0.0825c-9.861 84,检出限为5.35×10-9 mol/L。     

Electrochemical Detection of NADH,Cysteine, or Glutathione Using a Caffeic Acid Modified Glassy Carbon Electrode

A modified electrode was prepared using electrodeposition methods to immobilize caffeic acid (CAF) onto the surface of a glassy carbon electrode (GCE) to create a polymer suitable for biosensor development. The polymer film coverage of the surface bound species was further optimized using electrodeposition methods, thus increasing the surface coverage to ca. 10^?9 mol cm^?2. Using cyclic voltammetry, the modified carbon electrode was used to facilitate and observe the electrocatalytic oxidation of coenzymes such as NADH, cysteine, and glutathione at different concentrations. A calibration curve was determined in each case within the concentration range; 300 nM to 10 mM, with the limits of detection (LOD) of 246 µM, 99 µM, 2.2 µM for NADH, cysteine, and glutathione respectively.     

Speciation Analysis of Cr(III) and Cr(VI) after Solid Phase Extraction Using Modified Magnetite Nanoparticles

A new solid phase extraction (SPE) method has been developed for the speciation of Cr(III) and Cr(VI). This method is based on the adsorption of Cr(VI) on modified alumina‐coated magnetite nanoparticles (ACMNPs). Total chromium in different samples was determined as Cr(VI) after oxidation of Cr(III) to Cr(VI) using H₂O₂. The chromium concentration has been determined by flame atomic absorption spectrometric (FAAS) technique and amount of Cr(III) was calculated by substracting the concentration of Cr(VI) from total chromium concentration. The effect of parameters such as pH, amount of adsorbent, contact time, sample volume, eluent type, H₂O₂ concentration and cetyltrimethylammonium bromide (CTAB) concentration as modifier on the quantitative recovery of Cr(VI) were investigated. Under the optimal experimental conditions, the preconcentration factor, detection limit, linear range and relative standard deviation (RSD) of Cr(VI) were 140 (for 350 mL of sample solution), 0.083 ng mL^?1, 0.1‐10.0 ng mL^?1 and 4.6% (for 5.0 ng mL^?1, n = 7), respectively. This method avoided the time‐consuming column‐passing process of loading large volume samples in traditional SPE through the rapid isolation of CTAB@ACMNPs with an adscititious magnet. The proposed method was successfully applied to the determination and speciation of chromium in different water and wastewater samples and suitable recoveries were obtained.     

Preparation of PTFE Nanosphere with the Assistant of Modified Multi-Walled Carbon Nanotubes

PTFE nanospheres have been obtained with the assistant of different multi-walled carbon nanotubes (MWNTs) by means of a simple preparation method. The results show that the PTFE nanospheres possess the best dispersion stability using the fluorocarbon-modified MWNTs as the assistant. The products are characterized by field-emission scanning electron microscopy and X-ray photoelectron spectroscopy, respectively.     

Determination of direct orange 8 in effluent using a polypyrrole modified electrode

Electrochemical studies of direct orange 8 were carried out with a bare glassy carbon electrode (GCE) and a polypyrrole-coated GCE in aqueous acetonitrile medium using voltammetric techniques. One reversible couple around 0.3?V due to the redox reaction of the phenol group, one reduction peak around ?0.4?V due to reduction of the azo group and one oxidation peak around 1.0?V due to oxidation of the amino group were observed. Chronocoulometric studies revealed dye adsorption on the GCE. A square-wave stripping method was developed for the determination of the dye at pH 13.0, and a linear calibration equation obtained. The reproducibility in the measurement of peak currents was confirmed from the RSD value 2.8% at 0.001?mg?mL^?1 concentration. A comparison of the stripping voltammetric method with the UV-Vis spectrophotometric method was made. The determination limits are wider and the RSD value is lower in the stripping voltammetric method. The concentration of the dye present in dye effluent was determined using this method.     

Recent development of non-faradaic potentiometry

Non-faradaic potentiometry has been plagued by a great many fundamental errors and a lack of conceptualization. Of greatest concern is the second Nernst equation hiatus. Potentiometry may be generally classified as faradaic and non-faradaic. The former deals with the redox reactions using the Nernst equation to explain the potential origin. The latter deals with the non-redox reactions using the Boltzmann and modified Boltzmann equations to explain the origin of electrode potential. Redox faradaic potentiometry has been well described in the textbooks. However, non-faradaic potentiometry has been almost completely neglected in the literature. Many well-known electrodes, such as the pH glass electrode, common reference electrodes, and ion selective electrodes (ISE) have been mistakenly interpreted as redox reactions or ion exchange reactions. New theories and experimental results show their mechanisms to be non-faradaic in nature. Furthermore, the reaction mechanisms for ISE have been confused in textbooks with redox reactions and the Nernst equation. The ISE potentials originating from adsorption of ions or charged particles based on surface charge density will be explained using the double and counterion triple layers concept. The new counterion triple layer concept may be applied to the potential development of sensors. The reason for a new concept, theory, or mechanism is to better explain the phenomena. Examples will be given of how our new concept explains the capacitor, counterion triple layer, surface adsorbed layers interactions, and the interface structure. We will also discuss the new sensor development based on the new adsorption concept. For the first time a new type of Ag/AgCl reference electrode for non-faradaic potentiometry will be presented, one without a liquid junction and with a Pt wire instead of a salt bridge. They will help open up a new horizon for electrochemical sensor research and may be used under unusual conditions, such as high temperature and high pressure, stirring, etc.     

Development of an Amperometric Sensor Highly Selective For Dopamine and Analogous Compounds Determination Using Bis(2,2′‐Bipyridil) Copper(II) Chloride Complex

The use of [Cu(bipy)₂]Cl₂?6H₂O as a biomimetic catalyst in the construction of an amperometric sensor for dopamine determination is reported. The sensor was prepared modifying a glassy carbon electrode with a Nafion membrane doped with [Cu(bipy)₂]Cl₂?6H₂O complex. The sensor presented a higher response in 0.25 mol L^?1 phosphate buffer solution (pH 7.0), with an applied potential of ?50 mV (vs. SCE). In the optimized operational conditions, a linear response range between 35 and 240 μmol L^?1, with a sensitivity of 2.02±0.07 nA l μmoL^?1 cm^?2 and detection limit of 8.0 μmol L^?1 were typically observed for the sensor. The response time presented for this sensor was 0.5 s, presenting the same response for at least 40 successive measurements, with good repeatability (3.0%) expressed as relative standard deviation for n=6. The difference of the response between four sensor preparations was 4%. A detailed investigation about the sensor response for other sixteen phenolic compounds and interfering species were carried out. The sensor was applied in the determination of dopamine in pharmaceutical preparation with success.     

高选择性透过SO_2气体分离膜研究 Ⅰ.丙基乙烯基亚砜改性聚乙烯醇功能高分子的合成

本文研究聚乙烯醇与丙基乙烯基亚砜经Michael加成反应合成含亚砜基的改性聚乙烯醇功能高分子.用IR、~1H-NMR、X-射线衍射等鉴定反应产物.结果表明,随着亚砜基含量的增加聚合物的结晶性降低,而在冷水,DMSO,CH_3OH,C_2H_5OH和CH_2Cl_2中的溶解性提高.