Reagentless enzyme electrode for malate based on modified polymeric membranes

Abstract A series of polymeric membranes have been employed as outer barriers in an amperometric malate dehydrogenase (MDH)/diaphorase (DI) or MDH/DI/NAD + /mediator enzyme electrode for the determination of malate in undiluted neutral or acidic media. MDH/DI were physically entrapped with NAD + and mediator in a mixed ester cellulose membrane. Outer membranes such as non-anionic surfactant-modified cellulose acetate/Tween-80 and unplasticised spin coated PVC/polycarbonate (PC) resin in conjunction with an ascorbate oxidase (AOD) layer were utilised. Mechanical strength, thickness studies and diffusional properties of the membranes were investigated. Hexacyanoferrate(III), 2,4-dichlorophenolindophenol (DCPI) and naphthoquinone (NQ) were tested as mediators for enzymatically produced NADH using cyclic voltammetry. Analytical utility of the sensors is demonstrated

Intelligent and Distributed Data Warehouse for Student’s Academic Performance Analysis

In the academic world, a large amount of data is handled each day, ranging from student’s assessments to their socio-economic data. In order to analyze this historical information, an interesting alternative is to implement a Data Warehouse. However, Data Warehouses are not able to perform predictive analysis by themselves, so machine intelligence techniques can be used for sorting, grouping, and predicting based on historical information to improve the analysis quality. This work describes a Data Warehouse architecture to carry out an academic performance analysis of students

Performance of a Faradaic impedimetric immunosensor for blood group antigen A

The performance is described of a label-free Faradaic impedimetric immunosensor based on immobilized monoclonal IgM antibodies to blood group antigen A (anti-A) for blood typing. Anti-A was directly immobilized onto gold electrodes modified with an amine-reactive self assembled monolayer of dithiobis(succinimidylundecanoate). The alteration of the interfacial features of the electrodes due to different modification or recognition steps was probed by Faradaic impedance spectroscopy and cyclic voltammetry in the presence of a hexacyanoferrate(II)/(III) redox couple. Various optimization studies were undertaken with respect to the construction and potential use of the immunosensors as a diagnostic tool for blood typing.Microchimica Act

Development and study of anodic Ti/TiO2 electrodes and their potential use as impedimetric immunosensors

Titanium dioxide films were anodically formed at various potentials up to 65 V in 1M H2SO4. Oxide films were characterized by performing various techniques, including electrochemical impedance spectroscopy, scanning electron microscopy, Raman spectroscopy, ellipsometry and diffuse reflectance FT-IR spectroscopy. Low voltage anodization (up to 10V) results to amorphous TiO2, whereas at higher applied potentials (up to 65 V), anatase is the predominant form. Anatase films were further hydroxylated with an acidic agent and the effect of this treatment on the overall impedance of the electrodes was studied with impedance spectroscopy. The potential use of anodic (anatase) Ti/TiO2 electrodes in the development of impedimetric immunosensors is also demonstrated by monitoring the immunoreaction of avidin/anti-avidin with different instrumental approaches based on a FRA analyzer, an LCR-meter and a home-built charge integrator (Multipulser). (c) 2005 Elsevier Ltd. All rights reserved.Electrochimica Act

An electrochemical sensor for trace uranium determination based on 6-O-palmitoyl-L-ascorbic acid-modified graphite electrodes

The development of a preconcentrating sensor based on 6-O-palmitoyl-L-ascorbic acid (PAA)-modified graphite (GRA) electrodes for the determination of uranium is described. PM, a water insoluble compound of ascorbic acid, was immobilized onto the surface of the GRA electrodes through physical adsorption from acetone solutions. Uranium was accumulated by heterogeneous complexation (10 min, in 0.1 M H(3)BO(3), pH 4.3) and then, it was reduced by means of a differential pulse voltammetric scan in 0.1 M H(3)BO(3), pH 3.4. Alternatively, the performance of both preconcentration and voltammetric steps in a single run, at 0.1 M H(3)BO(3), pH 3.65, was also examined; however, in this case the observed current signals were lower by 30%. The experimental variables were investigated and under the selected conditions, a linear calibration curve in the range 2.7-67.5 mu g L(-1) U(VI) was constructed (r(2) = 0.9981). The 3 sigma limit of detection and the relative standard deviation of the method were 1.8 mu g L(-1) U(VI) and 8% (n = 5, 20 mu g L(-1) U(VI), preconcentration time 10 min), respectively. By increasing the preconcentration time to 30 min, a limit of detection as low as 0.26 mu g L(-1) U(VI) can be achieved. The effect of potential interferences was also examined. The accuracy of the method was established by recovery studies in inoculated tap and lake water samples. A simple and fast procedure based on filtering of the sample through a C-18 microcolumn was successfully used to remove the organic matter from the lake water samples. (C) 2011 Elsevier B.V. All rights reserved.Sensors and Actuators B-Chemica