Direct electron transfer reaction of glucose oxidase at bare silver electrodes and its application in analysis

The direct electron transfer reaction of glucose oxidase (GOx) at a bare silver electrode is verified. The electron transfer number n = 2, electron transfer coefficient α = 0.45 and rate constant of the electrochemical reaction K_s = 0.1 s⁻¹ are obtained. This communication presents a multimolecular adsorption model to explain the properties of the direct electron reaction between GOx and bare silver electrodes. The residual valence force may be an important factor to ensure a direct electron transfer reaction on the bare electrode. On the basis of the experimental fact that only biologically active GOx exhibits electrochemical activity in solution, a facile analytical method for analyzing the active GOx concentration is developed. The results determined correspond very well to that of a spectrometric method.     

流动注射在线萃取-火焰原子吸收法测定食用盐中的锌

基于锌与 1 (2 吡啶偶氮 ) 2 萘酚 (简称PAN)形成的配合物可被氯仿萃取 ,从高盐基体样品中分离富集锌 ,利用自行设计的分相器 ,实验确定了最佳的流动注射在线萃取 火焰原子吸收光度法测定锌的流路系统和化学反应条件。在选定的工作条件下 ,其RSD和检出限分别为 4 3 % (c=0 6 μg/mL ,n =1 1 )和0 0 3 μg/mL ,测定速度为 2 5样 /h。用于实际样品的测定 ,加标回收率为 97%～1 0 6 %。     

聚双环戊二烯反应注射成型

本文介绍了国外有关聚双环戊二烯反应注射成型的研究进展，讨论了国内进行聚双环戊二烯反应注射成型开发研究的现实意义，并对这一领域的发展进行了展望     

Spectrophotometric determination of total phenolics by solvent extraction and sorbent extraction optosensing using flow injection methodology

Flow injection analysis (FIA) procedures for the Spectrophotometric determination of phenol involving in-line concentration by solvent and sorbent extraction have been developed. The imine product formed in the reaction between phenol and 4-aminoantipyrine (4-AAP) is either extracted into chloroform (solvent extraction) or is temporarily retained on C₁₈-modified silica material contained in a microcolumn (sorbent extraction). In the latter case two variants of detection have been used namely the Spectrophotometric measurement of the methanolic eluent containing the concentrated dye and at-column optosensing of the retained reaction product followed by methanol elution to maintain reversibility of the process. In the solvent extraction procedure a 10-fold increase of sensitivity compared to the common FIA method without extraction is achieved but no corresponding improvement in detectability is observed. Under optimized conditions the detection limit amounts to 8 μg l⁻¹. Using sorbent extraction methodology, high concentration factors can be obtained when large sample volumes are used. The only limitation in getting correspondingly lower detection limits are an increasingly high and variable blank value with sampling volume. The detection limits obtained for measurement of the absorbance in the eluent and on-column optosensing are 11 μg l⁻¹ and 0.4 μg l⁻¹, respectively. A study of the extractability of various phenol derivates using both solvent and sorbent extraction revealed lower relative response rates compared to the FIA method without extraction. Phenolics that possess an additional acidic group are present in ionized form at the high pH of the assay and are not extractable at all.     

On-line sorption preconcentration of metals based on mixed micelle cloud point extraction prior to their determination with micellar chemiluminescence: Application to the determination of chromium at ng l levels

The on-line incorporation of cloud point extraction (CPE) to flow injection analysis (FIA) is modified to extract and preconcentrate metal species rapidly, avoiding the formation of hydrophobic complexes, using a mixed micellar medium. Coupling the procedure with chemiluminescence (CL) detection based on the catalytic activity of metal species on the luminol-hydrogen peroxide reaction and enhancing the signal with the presence of a micellar carrier containing bromide ions produces a powerful tool for the preconcentration and determination of metal species at ng l⁻¹ levels. As an analytical demonstration ultratrace concentrations of chromium were conveniently detected and quantified in samples with a complex matrix such as seawater and wastewater. The figures of merit for the determination of chromium were: 0.9-1.6% R.S.D. (n=5) with detection and quantification limits 0.5 and 2.0 ng l⁻¹, respectively. The calibration graph was rectilinear from 2 to 200 ng l⁻¹ (r=0.9996, n=6). Several other metal ions were determined in ideal situations, with analogous results.     

水中酚的膜萃取分离流动注射技术测定的研究

本文提出了硅橡胶膜在线萃取分离流动注射技术测定水样中苯酚的方法。由于水样中的苯酚透过硅橡胶进入萃取液的萃取量随时间的增加和温度的升高而增大，故采用停流技术及升高温度以降低酚的检出限。     

Potassium-selective optrode based on an immobilized fluorogenic crown ether

A new optical sensor phase for potassium ions has been developed based on the immobilization of the pH-dependent fluorogenic crown ether 4-acryloylamidobenzo-18-crown-6 on the non-ionic polymeric resin Amberlite XAD-2.Two different optical designs, a flow-through sensor and a fibre optic probetype sensor (optrode), have been constructed and their analytical performance characteristics have been evaluated. The resulting fluorimetric sensors for K⁺ ions exhibited detection limits of 0.4 or 0.8 M of K⁺ (16 g/l or 31 g/l), depending on the design, while the linear response occurred from 1 to 25 M of the metal concentrations. The precision, evaluated as the relative standard deviation of measurements of K⁺ levels at around ten times the detection limit (e.g. 5 M), turned out to be around ±2%.Advantageous features of this fluorimetric sensing phase and optrode include ease of construction, simplicity of use, reversibility, short response times (ca. 1 min full scale deflection) selectivity and operational stability, suitable for sensing potassium at low levels in complex matrices such as biological fluids.The fluorimetric optical sensor has been successfully applied to the direct determination of potassium in clinically important samples (serum and urine) and in natural waters. Very good accuracy has been obtained just using adequate synthetic aqueous potassium standards for calibration.     

离子选择电极—流动注射分析法动力学测定葡萄糖存在下的果糖

本文将离子电极与流动注射分析相结合，利用３０℃下，在强碱性介质中，果糖和葡萄糖与２，４－二硝基酚钠反应速度明显差异，动力学测定了葡萄糖存在下果糖的含量。自制了２，４－二硝基酚电极作为动力学电位测定用的工作电极。本法测定果糖的范围为０．０２～１．００ｍｏｌ／Ｌ，其ＲＳＤ为４．０％～４．９％，ＲＥ为１．０～５．０％；当Ｃ葡／Ｃ果≤３倍时，葡萄糖的干扰不超过５％；本法也曾成功地用于果葡萄浆测定，其ＲＳＤ     

金霉素的化学发光分析法研究

在碱性介质中，铜氨络离子去催化过氧化氢与金霉素的化学发光反应，表面活性剂 溴化十六烷基三甲基铵（ＣＴＭＡＢ）对该反应具有增敏作用．化学发光强度与金霉素的含量在 ４．０×１０－８～４．０×１０－６ｍｏｌ／Ｌ范围内呈线性关系；７次平行测定的相对标准偏差为１．７％～ ４．１％；标准加入回收率为９８．８％～１０１．ｌ％．应用于尿液中金霉素的测定，结果满意．     

四氢呋喃-水-乙醇三元溶液体系制备高合金化Pt-Ru/CMK-3催化剂

提出了在四氢呋喃(THF)、H2O和乙醇三元体系中用一般的化学还原法在室温下制备高合金化Pt-Ru/CMK-3催化剂的新方法. 与在纯水中制得的商品化ETEK催化剂相比, 其Pt-Ru粒子的合金化程度高、平均粒径较小且相对结晶度低, 因此, 该催化剂对甲醇氧化的电催化活性远高于在纯水中制得的Pt-Ru催化剂. 高合金化程度的原因是H2PtCl6和RuCl3在THF、H2O和乙醇三元溶液体系中的起始还原电位相近. 此外, CMK-3以其规整的二维有序孔道结构, 为直接甲醇燃烧电池(DMFC)中电子和物质的传输提供了方便的路径, 其巨大的比表面积也为Pt-Ru 纳米粒子的均匀分散提供了良好的载体.