Urease is the enzyme catalyzing the hydrolysis of urea into carbon dioxide and ammonia. This enzyme is substrate-specific, which means that the enzyme catalyzes the hydrolysis of urea only. This feature is a basic diagnostic criterion used in the determination of many bacteria species. Most of the methods utilized for detection of urease are based on analysis of its enzyme activity – the hydrolysis of urea. The aim of this work was to detect urease indirectly by spectrometric method and directly by voltammetric methods. As spectrometric method we used is called indophenol assay. The sensitivity of detection itself is not sufficient to analyse the samples without pre-concentration steps. Therefore we utilized adsorptive transfer stripping technique coupled with differential pulse voltammetry to detect urease. The influence of accumulation time, pH of supporting electrolyte and concentration of urease on the enzyme peak height was investigated. Under the optimized experimental conditions (0.2 M acetate buffer pH 4.6 and accumulation time of 120 s) the detection limit of urease evaluated as 3 S/N was 200 ng/ml. The activity of urease enzyme depends on the presence of nickel. Thus the influence of nickel(II) ions on electrochemical response of the enzyme was studied. Based on the results obtained the interaction of nickel(II) ions and urease can be determined using electrochemical methods. Therefore we prepared Ni nanoelectrodes to measure urease. The Ni nanoelectrodes was analysed after the template dissolution by scanning electron microscopy. The results shown vertically aligned Ni nanopillars almost covered the electrode surface, whereas the defect places are minor and insignificant in comparison with total electrode surface. We were able to not only detect urease itself but also to distinguish its native and denatured form.
In the contribution, it has been demonstrated that Elimination Voltammetry with Linear Scan (EVLS) introduces an enhancement of the linear sweep and/or cyclic voltammetric results, and provides information about the type of the currents involved in the considered process. An extension of EVLS has been developed for any combination of scan rates (integers) for six elimination functions that are capable of conserving or eliminating of some voltammetric current components. Simple procedure to obtain the necessary coefficients from the chosen scan rates has been reported. In addition, the calculation and discussion of the relative error of elimination function (REEF) have been presented. The verification of the presented calculations has been done by studying different ratios of scan rates for reduction and oxidation processes of Cd(II) at a hanging mercury drop electrode (HMDE).
Elimination voltammetry with linear scan (EVLS) in connection with renewed mini-drop mercury electrodes provides valuable information about the character and kinetics of processes at electrode/electrolyte interfaces. Based on the experiment related to the hydrogen evolution, it is presented that the EVLS is more sensitive than other voltammetric methods. Using miniaturized mercury electrodes, the EVLS is capable of detecting the effect of spherical diffusion associated with both the scan rates and the size of an electrode drop.
Nanostructures have recently attracted great interest because of their unique properties and potential use in a broad range of technological applications. In the case of electrochemical microsensors, an array of nanostructures can be used to enlarge the surface area of sensing electrodes and it also has a positive impact on the redox reactions on their surfaces. It is assumed that these microsensors will then have higher sensitivity due to the surface modification. One of the easiest ways to modify an electrode surface by nanostructures is to deposit a metal into a thin nanoporous Al2O3 template which is placed on a gold electrode. Metal ions are attracted to the cathode (the gold electrode) during electrodeposition and fill the nanopores in the template. After completing the electrodeposition process, the template is dissolved and the metal nanostructures are obtained. Both nanorods and nanotubes of various wall‐thicknesses can be created by this method. It has been found that the type of the nanostructure depends on specific electroplating conditions (e.g. pH and concentration) and used template (i.e. diameters of the nanopores). Therefore, it is possible to control the type of the nanostructure by adjusting these electroplating parameters and to create either nanorods or nanotubes on purpose. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A novel time of flight SIMS analyzer provides a new approach to SIMS analysis as an addition to a focused ion beam SEM instrument. The combination of this analyzer with a high current plasma ion source offers new opportunities for analysis, particularly in the study of coatings, which require ultra-deep profiling. Use of this instrumentation showed the ability to detect and quantify a number of elements. Quantification was obtained for Li, Na, K ion implanted in Si and for B in a sample with known concentration. Use of the electron beam from the electron column permitted analysis of 300-nm SiO 2 /Si implanted with BF 2 .
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