Electrochemical stripping analysis

Electrochemical stripping analysis (ESA) is a trace electroanalytical technique for the determination of metal cations, inorganic ions, organic compounds and biomolecules. It is based on a pre-concentration step of the target analyte(s), or a compound of the target, on a suitable working electrode. This is followed by a stripping step of the accumulated analyte using an electroanalytical technique. Advantages of ESA include high sensitivity and low limits of detection, multi-analyte capability, low cost of instrumentation and consumables, low power requirements, potential for on-site analysis, speciation capability and scope for indirect biosensing. This Primer covers fundamental aspects of ESA and discusses methods of pre-concentration and stripping, instrumentation, types of working electrodes and sensors, guidelines for method optimization, typical applications, data interpretation and interferences, and method limitations and workarounds. Finally, the current trends and future prospects of ESA are highlighted

Diagnostics of Anodic Stripping Mechanisms under Square-Wave Voltammetry Conditions Using Bismuth Film Substrates

A mechanistic study to provide diagnostics of anodic stripping electrode processes at bismuth-film electrodes is presented from both theoretical and experimental points of view. Theoretical models for three types of electrode mechanisms are developed under conditions of square-wave voltammetry, combining rigorous modeling based on integral equations and the step function method, resulting in derivation of a single numerical recurrent formula to predict the outcome of the voltammetric experiment. In the course of the deposition step, it has been assumed that a uniform film of the metal analyte is formed on the bismuth substrate, in situ deposited onto a glassy carbon electrode surface, without considering mass transfer within either the bismuth or the metal analyte film. Theoretical data are analyzed in terms of dimensionless critical parameters related with electrode kinetics, mass transfer, adsorption equilibria, and possible lateral interactions within the deposited metal particles. Theoretical analysis enables definition of simple criteria for differentiation and characterization of electrode processes. Comparing theoretical and experimental data, anodic stripping processes of zinc(II), cadmium(II), and lead(II) are successfully characterized, revealing significant differences in their reaction pathways. The proposed easy-to-perform diagnostic route is considered to be of a general use while the bismuth film exploited in this study served as a convenient nonmercury model substrate surface

Characterization of mercury cadmium telluride (Hg_1-XCd_XTe) epitaxial layers using the manufactured photodiodes

Celem pracy było opanowanie metody szybkiej charakteryzacji fotodiod z tellurku kadmowo-rtęciowego - HgCdTe - otrzymywanych metodą MOCYD (Metal Organie Chemical Vapor Depositiori) tzn. techniką osadzania warstw na powierzchni materiałów poprzez stosowanie związków metaloorganicznych w formie gazowej oraz analiza tej metody. W pierwszej kolejności otrzymane warstwy epitaksjalne poddawano procesowi technologicznemu i w ten sposób uzyskiwano gotowe fotodiody. Dokonano też pomiarów czasu trwania poszczególnych etapów procesu technologicznego. Uzyskane detektory poddawano następnie pomiarom w celu wyznaczenia ich charakterystyk prądowo-napięciowych oraz spektralnych. Na podstawie analizy tych charakterystyk oraz z wykonanych obliczeń otrzymano parametry diod, które następnie porównano z parametrami na jakie zaprojektowano heterostruktury oraz z wartościami literaturowymi. Zarówno w tym przypadku, jak i podczas przeprowadzania procesu technologicznego dążono do jak największego zminimalizowania czasu potrzebnego na wykonanie każdego etapu przy jednoczesnym zachowaniu staranności i dokładności wykonywanych czynności. Istotą postępowania było bowiem jak najszybsze uzyskanie informacji zwrotnej dotyczącej parametrów otrzymanych heterostruktur w celu porównania ich z założeniami wstępnymi i ewentualnego szybkiego skorygowania procesu epitaksji, dążąc tym samym do jego usprawnienia.The aim of this study was to master a method for a quick characterization of mercury cadmium telluride (HgCdTe) photodiodes obtained by MOCVD (Metal Organic Chemical Vapor Deposition) method, which was achieved. First, the obtained epitaxial layers were subjected to the technological process procedures and thus complete photodiodes were fabricated. The duration of measurements of each process stage was quantified. Detectors were then measured to determine their current-voltage and spectral characteristics. On the basis of the analysis of both these characteristics and calculations, the parameters of diodes were obtained. They were subsequently compared with the parameters of designed target heterostructures and with literature values. Both here and during the process the goal was to minimize as much as possible the time needed to complete each stage, while maintaining diligence and accuracy of the performed operations. The essence was to be provided with rapid feedback concerning the parameters of the obtained heterostructures in order to compare them with the initial assumptions and, if needed to correct next epitaxy processes, aiming at their improvement

State equations in the mathematical model of dynamic behaviour of multihull floating unit

This paper concerns dynamic behaviour of multihull floating unit of catamaran type exposed to excitations due to irregular sea waves. Dynamic analysis of multihull floating unit necessitates, in its initial stage, to determine physical model of the unit and next to assume an identified mathematical model. Correctly elaborated physical models should contain information on the basis of which a mathematical model could be built. Mathematical models describe mutual relations between crucial quantities which characterize a given system in time domain. The dynamic analysis of multihull unit was performed under assumption that the unit’s model has been linear and exposed to action of irregular sea waves. Mathematical model of such dynamic system is represented by state equations. The formulated equations take into account encounter of head wave which generates symmetrical motions of the unit, i.e. surge, heave and pitch. For solving the equations the following three wave spectra were taken into consideration: - ISSC (International Ship Structures Congress) spectrum - Pierson-Moskowitz spectrum - Paszkiewicz spectrum

Investigation of growing grains in microstructure of the 61SiCr7 spring steel

The article presents results from determination of a grain size in microstructure of the 61SiCr7 (60C2A) spring steel. The material was selected with respect to the possibility of obtaining a nano-structured bainite without carbide precipitates. This was conducted basing on an influence of grain size on bainitic transformation time, microstructure and mechanical properties of the material type considered. The experiments indicated, that the addition of silicon caused difficulties related to revealing the grain boundaries of the austenite. Optimal parameters of heat treatment, which enable to reach the microstructure for observing grain sizes of the steel are shown. The growing grains of the tested steel was followed at five values of austenitizing temperature

Multihull vessel excitations in stochastic formulation

The article analyses excitations of a multihull vessel using stochastic formulation. The excitations which make the vessel move come from the motion of sea waves and the action of wind. The sea undulation has most frequently the form of irregular waves, and that is why it is assumed in many studies of sea-going vessel dynamics that the undulation process has probabilistic nature. In the article the dynamics of a multihull vessel is analysed using a linear model on which an irregular wave acts. It was assumed that the examined object interacts with the head sea, and for this wave a set of state equations was derived. The head sea provokes symmetric movements of the object, i.e. surge, heave and pitch

Distribution of hydrodynamic pressure on walls a tanks vibrations

W artykule przedstawiono przyczyny powstawania drgań w transporcie morskim. W zbiornikach ładunkowych na zbiornikowcach czy statkach LNG znajduje się ciecz. Drgające zbiorniki wywołują ruch cieczy, który indukuje ciśnienia hydrodynamiczne na ściankach konstrukcyjnych zbiorników. Na podstawie analizy teoretycznej w ramach teorii liniowej i nieliniowej wyznaczono potencjały prędkości ruchu cieczy. Znając funkcje potencjału prędkości cieczy otrzymano rozkłady ciśnień hydrodynamicznych na ściankach zbiorników. Na końcu podano wykresy rozkładów ciśnień dla obu teorii w funkcji częstości drgań.The article presents causes of vibration in maritime transport. There is liquid in cargo tank on tankers or LNG vessels. The vibrations reservoirs cause a movement of the liquid that induces hydrodynamic pressure on the tank walls. On the basis of theoretical analysis, linear velocity and nonlinear theories have been determined for the potential of velocity liquid motion. Knowing the functions of the fluid velocity potential, hydrodynamic pressure distributions have been obtained on tank walls. At the end, pressure plots for both theories as a function of vibration frequencies are given

Motion of liquid at tank in the rotation motion

W artykule omówiony został ruch ładunku płynnego w zbiorniku podczas obrotu. Przeprowadzono analizę teoretyczną wg teorii liniowej i nieliniowej. Wyznaczono potencjał prędkości cieczy i na tej podstawie funkcję ciśnienia w dowolnym punkcie objętości cieczy w zbiorniku. Podano wykresy obciążeń ścianek zbiornika od cieczy wg obydwu teorii.The article discussed a motion of liquid cargo in tank during rotation. The conducted are of theoretical analysis according linear and non-linear theory. Was designated the potential of velocity of the liquid and on the basis of pressure function at any point liquid of volume in tank. Are given of load charts walls of tank of liquid according to both theories

Hydrodynamic load of subsea construction elements

W artykule dokonano analizy hydrodynamicznej elementu konstrukcji podwodnej. Konstrukcja posadowiona jest na dnie morza w strefie brzegowej. Dno jest gruntem nieprzepuszczalnym wody. Elementy konstrukcji podwodnej mają kształt „nóg” jak na rys.1. Falowanie wody wywołuje pole ciśnień na elementy podwodne. Obciążenia hydrodynamiczne na powierzchniach zwilżonych wyznaczono przez całkowanie rozkładów ciśnień. Są to siły poziome i pionowe. Przy braku falowania występują tylko siły poziome wywołane ciśnieniem hydrostatycznym i siły pionowe działające na wierzch konstrukcji zanurzonej.The article analyzes the hydrodynamic underwater structure element. The structure is placed on the seabed in the coastal zone. The bottom is impermeable ground water. Elements of underwater structure are shaped "legs" as in Figure 1. Water ripple causes pressure field on underwater elements. Hydrodynamic loads on wetted surfaces were determined by integrating the pressure distribution. These forces are horizontal and vertical. In the absence of waves occur only horizontal forces caused by hydrostatic pressure and vertical forces acting on the top of the submerged structure