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

Screen-printed disposable sensors modified with bismuth precursors for rapid voltammetric determination of 3 ecotoxic nitrophenols

This work reports the application of screen-printed electrodes bulk-modified with bismuth precursors to the voltammetric determination of 2-nitrophenol (2-NP), 4-nitrophenol (4-NP) and 2,4-dinitrophenol (2,4-DNP) in water samples. A bismuth film was formed at the electrode surface via in situ reduction of the precursor compound contained in the electrode matrix by cathodic polarization at -1.20V. The formation of bismuth layer at the precursor-modified electrodes was assessed by cyclic voltammetric (CV) at different pH values and by optical techniques. The target nitrophenols were voltammetrically determined by recording their reduction peaks in the differential pulse (DP) mode. The composition and content of the precursor compounds in the printed ink and the effect of the pH of the supporting electrolyte on the DP reduction currents of the 3 target nitrophenols were studied. The limits of quantification (LOQs) in three water matrices (distilled water, tap water and surface water) were in the range 1.1-2.2μmolL-1. Using a simple solid-phase extraction (SPE) procedure with Lichrolut EN cartridges and elution with methanol, a preconcentration factor of 100 was achieved; the LOQs were 0.021, 0.027 and 0.025μmolL-1 for 2-NP, 4-NP and 2,4-DNP, respectively. The recoveries of samples spiked with the 3 target nitrophenols at two concentration levels (0.04 and 0.1μmolL-1) were always >87%. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Novel screen-printed antimony and tin voltammetric sensors for anodic stripping detection of Pb(II) and Cd(II)

In this article, some new types of electroplated and precursor-modified screen-printed antimony and tin electrodes were developed and assessed for the simultaneous anodic stripping voltammetric (ASV) detection of Pb(II) and Cd(II). The electrodes were characterized by cyclic voltammetry and the different instrumental and chemical parameters were investigated. A comprehensive comparison of the new sensors was performed against the benchmark electroplated and precursor-modified screen-printed bismuth electrodes. The limits of detection were in the range 0.9 to 1.2 μg L-1 for Pb(II) and 1.8 to 3.5 μg L-1 for Cd(II) for 240 s deposition. The repeatability on the same sensor (expressed as % relative standard deviation, (n = 8)) at the 20 μg L-1 level was always lower than 5.7% and 8.3% for the electroplated and the precursor-modified electrodes, respectively. Application of the new sensors to mineral water samples spiked with Cd(II) and Pb(II) produced % recovery values in the range 95% to 103%. © 2013 Elsevier Ltd