Development of an amperometric flow injection immunoanalysis system for the determination of the herbicide 2,4-dichlorophenoxyacetic acid in water

An amperometric flow injection immunoanalysis (FIIA) system based on an immunoreactor with immobilized biocomponents on a silica surface has been developed for the determination of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). In the antigen coating mode the hapten was immobilized and monoclonal primary antibody against 2,4-D together with alkaline phosphatase (AP)-labelled secondary antibody were used as sensing elements in a titration assay. In the antibody coating mode a biotinylated monoclonal antibody was immobilized on the surface of the immunoreactor and a 2,4-D-AP-conjugate was used for detection. For electrochemical measurements p-aminophenol enzymatically generated from p-aminophenyl phosphate was oxidized at a carbon working electrode at +150 mV versus Ag/AgCl. The system enabled the determination of 2,4-D in drinking water samples in the range from 0.2 to 70 micrograms/l. The whole system was computer controlled with a measuring time of 12 min for one determination.     

Anodic coulometric detection with a glassy carbon electrode in combination with reversed-phase high-performance liquid chromatography. Determination of blood levels of perphenazine and fluphenazine

A detector for liquid chromatography, based on anodic electrochemical oxidation at a glassy carbon electrode, is used in combination with reversed-phase liquid chromatography for the determination of the long-acting tricyclic psychotropic drugs fluphenazine and perphenazine in blood. Completely porous microparticulate silica material, modified so as to give a methyl silica, was used as the stationary phase and buffered mixtures of methanol and water as the mobile phase. The low detection limit and the selectivity of the coulometric detector made possible the determination of concentrations of 1-20 ppb of the compounds of interest. An extraction procedure was in order to obtain sufficient selectivity. Data for the precision, detection limit and yield of the extraction procedure are given. A number of serum levels of perphenazine after oral administration and of fluphenazine after i.m. doses of fluphenazine decanoate are stated.     

纳米金-石墨烯修饰碳糊电极微分脉冲溶出伏安法检测水中铅

构建纳米金(Au)-石墨烯(GS)修饰碳糊电极(CPE)的电化学传感器(CPE│GS/Au),建立微分脉冲溶出伏安(DPSV)法测定痕量铅的电化学分析方法。采用扫描电镜(SEM)表征GS和电极的制备过程,采用DPSV法研究铅的电化学性质。在优化的实验条件下,溶出峰电流与Pb2+浓度在2×10-10~5×10-8 g/mL范围内呈良好的线性关系,线性相关系数为0.999 0,检出限为1.2×10-10 g/mL。用于实际水样分析,与石墨炉原子吸收光谱(GF-AAS)法所得结果一致,相对标准偏差(RSD)小于4.3%。该传感器采用复合纳米微粒修饰CPE,扩增了响应电流且一次使用可抛弃、分析成本低,具有较好的制备重复性。     

Electrocatalytic surface for the oxidation of NADH and other anionic molecules of biological significance

A simple electrochemical treatment of a carbon fiber electrode surface has been found to dramatically improve the voltammetry of NADH and several other anionic molecules under steady-state and fast scan (100 V/s) conditions. The electrocatalytic surface is generated through the electrochemical oxidation of NADH on a carbon fiber electrode that exhibits product adsorption. The oxidative product is reacted with ascorbic acid at elevated temperatures to create a surface which has very little overpotential for the oxidation of dopamine and many metabolites such as NADH, DOPAC, uric acid, and ascorbate. The electrochemical properties of the modified surface were examined voltammetrically at both slow and fast scan rates. The surface shown in this paper shifts the oxidation overpotentials different magnitudes for each analyte tested, thus allowing discrimination between analytes of interest and their major interferences. Another benefit of this new electrocatalytic wave is that it decreases the limit of detection for NADH by approximately 1 order of magnitude. Therefore, this new carbon surface not only gives better discrimination between two analytes but also gives better detection limits for certain analytes of interest.     

Electrooxidation of thiocyanate on the copper-modified gold electrode and its amperometric determination by ion chromatography

Cyclic voltammetry was used to investigate the electrochemical behavior of an Au/Cu electrode towards the electrooxidation of thiocyanate ion in alkaline medium. The effects of pH, copper loading, scan rate and applied potential on the electrocatalytic oxidation of thiocyanate have been investigated. Flow injection experiments and ion-chromatography (IC) were performed to characterise the electrode as an amperometric sensor for the thiocyanate determination. The effects of carbonate concentration and common interferents on the retention time were also estimated. The electrode stability, precision, limit of detection and linear range were evaluated at a constant applied potential of 0.7 V vs. Ag/AgCl. Calibration plots, obtained in IC, were linear from 1.0 to 195 microM (correlation coefficient of 0.9984). The detection limit (LOD) was 0.5 microM (29 ppb) in a 50 microlitres injection. An example of analytical application, which includes the IC separation and detection of thiocyanate ion present in human urine, is given.     

电化学还原石墨烯修饰玻碳电极测定痕量银

在玻碳电极表面,用电化学还原氧化石墨烯,制备了石墨烯修饰玻碳电极。通过优化支持电解质及其pH值、修饰剂用量、富集电位及时间等测定条件,建立了基于该电极测定痕量银的线性扫描阳极溶出伏安分析法。含痕量银溶液在pH 4.0的NaAc-HAc缓冲液中,-0.10 V电位下富集5 min后,于0.32 V处出现一灵敏度高、峰形较好的银阳极溶出峰,溶出峰电流与Ag⁺浓度在1.0×10^-7 ~ 4.0×10^-5 mol/L范围内线性关系良好,检出限为3.0×10^-8 mol/L(S/N=3)。方法用于环境水样中痕量银的测定,平均回收率在95%~107%之间。     

Thick-film electrochemical immunosensor based on stripping potentiometric detection of a metal ion label

A disposable electrochemical immunosensor based on potentiometric stripping analysis (PSA) of a metal tracer and using an entirely on-chip assay format is demonstrated. Challenges associated with the adaptation of earlier stripping voltammetric immunoassays to an on-chip operation, and with meeting the demands of decentralized testing, have been addressed. These include the surface immobilization of the antibody, the replacement of mercury drop electrodes, elimination of the separation and oxygen-removal steps, and the use of quiescent 30-microL sample droplets. Human serum albumin (HSA) and anti-HSA antibody were used as a model system, while bismuth ion served as the metal label. The anti-HSA was immobilized onto the surface of a thick-film electrode, followed by a competition between the Bi-labeled analyte-tracer and the analyte (HSA) for the antibody binding sites. Upon removal of the unbound tracer, Bi3+ was released and detected by PSA. The dynamic concentration range for HSA (0.3-30 micrograms/mL) and the detection limit (0.2 microgram/mL, i.e., 90 fmol in the 30-microL sample) indicate that the greatly simplified protocol does not compromise the performance characteristics of stripping immunoassays. Consequently, this on-chip operation offers great promise for decentralized (clinical and environmental) applications.     

电感耦合等离子体原子发射光谱法测定载金树脂物料中银含量

载金树脂物料经高温灰化后, 用王水溶解残渣, 选择328.628 nm波长的光谱线作为银的分析线, 采用电感耦合等离子体原子发射光谱法(ICP-AES)测定了试液中的银。金、铁、铝、硅、硫等基体元素产生的基体效应采用基体匹配的方法克服。方法的检出限为0.008 1 μg/mL, 样品测定结果的相对标准偏差在5.1%～7.3%范围, 回收率在93.4%～103.4%之间。方法简便、快速、可靠, 可用于进口载金树脂物料样品中银的测定。     

高频燃烧红外吸收法测定氮化钒铁中碳和硫

对于含氮量较高的氮化钒铁而言,其熔点高达1 450～1 650 ℃,给测定碳和硫的含量带来难题。利用钒铁标准物质建立校准曲线,钒铁标准物质进行校准验证,设定分析时间为50 s,以0.4 g纯铁和1.4 g钨粒为助熔剂进行助熔,建立了高频燃烧红外吸收法测定氮化钒铁中碳和硫的分析方法。方法中碳和硫的检出限分别为0.001 1%和0.001 3%,方法测定下限分别为0.003 5%和0.004 2%。由于缺乏氮化钒铁标准物质,取一定量的钒铁标准物质,分别与氮化硅铁标准物质混合,参照FeV45N10、FeV55N11氮化钒铁的成分配比配制氮化钒铁合成样品1#和2#,按照实验方法进行测定,所得测定值和理论值基本一致。实验方法测定氮化钒铁样品中碳含量结果的相对标准偏差(RSD,n=8)在1.2 %～3.0%之间,硫在2.2%～4.2%之间。     

A procedure for the determination of 5-fluorouracil in tissue using microbore HPLC and fluorescence detection

For the determination of the cytotoxic drug 5-fluorouracil in tissue, a sensitive and selective assay has been developed based on microbore high-performance liquid chromatography and fluorescence detection after pre-column derivatization with 4-bromomethyl-7-methoxycoumarin. 5-Chlorouracil was found to be an appropriate internal standard. A column switching protocol has been devised to separate the analyte from late eluting matrix components and the natural uracil. The drug can be determined at concentrations in the low ng/g wet tissue range with a detection limit of 3 ng/g; furthermore, the same protocol can be applied to analyze serum and plasma samples. The procedure was employed to determine the drug in samples taken from human liver tumors and metastases after an intra-arterial bolus administration and from epithelial carcinomas after systemic continuous application.     

聚L-天冬氨酸/多壁碳纳米管复合膜修饰玻碳电极测定亚硝酸根

采用滴涂法和电聚合法制备了聚L-天冬氨酸/多壁碳纳米管复合膜修饰玻碳电极,利用循环伏安(CV)法研究了亚硝酸根 ( NO^-₂) 在该修饰电极上的电化学行为,建立了一种电化学测定NO^-₂的新方法。实验结果表明,该修饰电极对于 NO^-₂的氧化具有良好的电催化性能,并且显著促进 NO^-₂在电极表面的电化学过程。利用差分脉冲伏安法测定,在2.0 × 10^-6~2.0 × 10^-4 mol/L浓度范围内,NO^-₂的氧化峰电流与浓度呈现良好的线性关系,相关系数为 0.998 9。信噪比为 3 时,NO^-₂的检出限为 2.0 × 10^-7 mol/L。方法成功地用于环境水样中NO^-₂测定。     

An immunosensor based on disposable electrodes for rapid estimation of fatty acid-binding protein, an early marker of myocardial infarction

An immunosensor was developed that allows the rapid estimation of fatty acid-binding protein (FABP) in neat plasma samples. FABP is released into the blood following myocardial infarction and elevated levels are found already 3 h after onset of symptoms. The sensor is based on screen-printed graphite working and Ag/AgCl reference electrodes and an immunosandwich procedure for the quantification of FABP. The capture antibodies are bound to the electrode surface by adsorption and will trap FABP from the plasma sample. The sandwich is then completed by a second monoclonal antibody conjugated with alkaline phosphatase. The enzyme converts p-aminophenylphosphate to p-aminophenol, which is detected amperometrically at +350 mV. The high binding capacity and very short response time of the working electrode allow within 20 min the quantification of FABP in the measuring range 10-350 ng/ml, covering the pathological range of FABP release into the circulation. Measurements of plasma samples from a patient with acute myocardial infarction show an excellent correlation of the results obtained with the biosensor and those obtained with the respective reference ELISA. Owing to the long stability of the electrodes with immobilized capture antibody (> 3 months) a quick application without the need of labour-intensive electrode preparation is possible.     

Detection of protein A produced by Staphylococcus aureus with a fiber-optic-based biosensor

Staphylococcus aureus is a pathogen important in causing human infections and intoxication. A sensitive fiber-optic that produces evanescent waves was developed for the detection of protein A, a product secreted only by S. aureus. In the immunosensor, a 40-mV argon-ion laser that generated laser light at 488 nm was used together with plastic optical fiber and antibodies to protein A were physically adsorbed onto the fiber. The principle of the detection involved a sandwich immunoassay with fluorescein isothiocyanate conjugated with anti-(protein A) immunoglobulin G to produce signals of the antigen-antibody reaction. The detection limit was 1 ng of protein A per milliliter. The fiber-optic immunosensor could be used for rapid and specific detection of S. aureus in clinical specimens and foods.     

Trace Determination of Scandium Using Adsorption Voltammetry of Mix-Polynuclear Complex of Scandium-Calcium-Alizarin Red S at Carbon Paste Electrode

Scandiumisatypicaldispersalelement,whichiswidelydispersedinnature .Ithasbeenwidelyusedinthefieldsofmetallurgicalindustry ,chemicalindustry ,electronicsandelectrotechnics ,energysources ,radia tionchemistry ,etc .Scandium ,likeyttriumandmanyotherrareearthelements ,cannotbeeasilydeterminedbyconventionalvoltammetry ,evenifatamercuryelectrodewithhighhydrogenoverpotentialandinalka linesolution ,becauseitsreductionpotentialisclosetothereductionpotentialofhydrogen[1] .Advancingofthepolarographiccompl…     

用聚苏木精/TiO2-石墨烯复合膜修饰玻碳电极差分脉冲伏安法测定水样中对苯二酚

采用滴涂法和电聚合法制备了聚苏木精/TiO2-石墨烯复合膜修饰玻碳电极。用循环伏安法研究了对苯二酚（HQ)在修饰电极上的电化学行为。实验结果表明,该修饰电极对于HQ的氧化还原具有良好的电催化性能。相对于裸电极和TiO2-石墨烯修饰电极,HQ在聚苏木精/TiO2-石墨烯修饰玻碳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在3.0×10-6~1.0×10-3 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0.993。信噪比为3时,HQ检出限为1.0×10-7 mol/L。将该方法用于环境水样分析,回收率为96.2% ~ 105.6%。     

苏木精和石墨烯修饰玻碳电极差分脉冲伏安法测定铜

石墨烯通过滴涂法固定在玻碳电极上,苏木精通过电聚合在石墨烯表面形成聚合膜,依托该修饰电极建立了差分脉冲伏安法测定痕量铜的电化学分析法。在0.1 mol/L pH 4.2的NaAc-HAc缓冲液中,于-0.3 V处搅拌富集4 min,测定0.13 V处的峰电流。峰电流与Cu2+的浓度在5×10-8~2×10-7 mol/L和2×10-7~5×10-6 mol/L范围内呈良好的线性关系,相关系数为0.992和0.996。方法的检出限为2×10-9 mol/L。将该法用于工业废水中痕量铜的测定,与ICP-AES法的测定结果相一致,相对标准偏差为4.3%~5.7%。     

Ethological analysis of cholecystokinin (CCKA and CCKB) receptor ligands in the elevated plus-maze test of anxiety in mice

Membranes for determination of maltose, lactose and sucrose with the use of an oxygen electrode are described. They were obtained by immobilization of glucose oxidase with suitable disaccharide hydrolase in gelatin or albumin. For the sucrose determination mutarotase was also used. The membranes contained one, two or three enzymes working in sequence. The enzyme composition of the membranes influenced the linear range slightly and the value of electrode response considerably. The electrode response of the maltose membranes was also affected by the immobilization material. The measurements with the use of enzymatic membranes were very sensitive to temperature and, to some degree, the pH of the sample. Stability of the membranes was differentiated. The albumin membranes for sucrose determination generated almost the same signal after 1 month of frequent use, whereas the gelatin membranes for lactose determination lost about 85% of the initial activity after 1 week of operation. The electrode response of both the gelatin and albumin maltose membranes decreased in the same time by about 50%.     

Rat fetal ventral mesencephalon grown as solid tissue cultures: influence of culture time and BDNF treatment on dopamine neuron survival and function

The method of analysis described permits the determination of 2,4-dinitrobenzoic acid down to the lower microg l(-1) range in the urine of persons exposed to dinitrotoluene. 2,4-Dinitrobenzoic acid is the main metabolite of 2,4-dinitrotoluene and technical dinitrotoluene. After acidic hydrolysis, which served to release the conjugated part of the 2,4-dinitrobenzoic acid, the analyte was selectively separated from the urine matrix via various extraction steps and then derivatised to the methyl ester. Quantitative analysis was carried out using capillary gas chromatography and mass selective detection. 3,5-Dinitrobenzoic acid was used as an internal standard. The detection limit was 1 microg l(-1) urine. The relative standard deviations of within-series imprecision were between 5 and 6%. The relative recoveries were between 91 and 110% depending on the concentration. The analytical method developed as part of this study was used to investigate a collective consisting of 82 urine samples from persons working in the area of explosives disposal. The concentrations of 2,4-dinitrobenzoic acid determined ranged from the detection limit to 95 microg l(-1) urine. The method allowed the quantification of low-level internal exposure to dinitrotoluene.     

Chemiluminescence flow-through sensor for copper based on an anodic stripping voltammetric flow cell and an ion-exchange column with immobilized reagents

A novel chemiluminescence (CL) flow-through sensor based on immobilizing all the ingredients involved in the analytical reaction for the determination of copper is proposed. The analytical reagents including luminol and cyanide were coimmobilized permanently on an anion-exchange column, while the analyte copper was retained temporarily by electrochemical preconcentration on a gold electrode placed in an anodic stripping voltammetric flow cell. By injection of a volume of sodium hydroxide through the column with immobilized reagents, luminol and cyanide were eluted from the resins in alkaline aqueous solution and then reacted with copper stripped from the gold electrode to produce a CL signal, by means of which copper could be sensed. The sensor was not susceptible to interference by other metal ions associated with the CL reaction. The response to the concentration of copper was linear in the range of 0.01-10 micrograms/L and an extremely low detection limit of 8.0 x 10(-3) micrograms/L was achieved. A complete analysis could be performed in 4 min with a relative standard deviation of less than 8%. The column with immobilized reagents was readily prepared and could be reused over 200 times. The sensor was applied successfully to the determination of copper in human serum and natural water samples.     

An array immunosensor for simultaneous detection of clinical analytes

A fluorescence-based immunosensor has been developed for simultaneous analysis of multiple samples. A patterned array of recognition elements immobilized on the surface of a planar waveguide is used to "capture" analyte present in samples; bound analyte is then quantified by means of fluorescent detector molecules. Upon excitation of the fluorescent label by a small diode laser, a CCD camera detects the pattern of fluorescent antigen:antibody complexes on the sensor surface. Image analysis software correlates the position of fluorescent signals with the identity of the analyte. This immunosensor was used to detect physiologically relevant concentrations of staphylococcal enterotoxin B (SEB), F1 antigen from Yersinia pestis, and D-dimer, a marker of sepsis and thrombotic disorders, in spiked clinical samples.