ANALYSIS OF VOLTAMPEROGRAMS OF OXIDATION-REDUCTION PROCESSES WITH LABVIEW MEANS
Authors:   Kremenchuk Mykhailo Ostrohradskyi National University, Mospan Vladyslav , Yurko Alexey ,   Kremenchuk Mykhailo Ostrohradskyi National University, Kukharenko Dmitriy ,   Kremenchuk Mykhailo Ostrohradskyi National University, Gladkyi Viktor ,   Kremenchuk Mykhailo Ostrohradskyi National University, Sankov Sergii ,   Kremenchuk Mykhailo Ostrohradskyi National University
Published: May 2022

Purpose. In the analysis of voltammetograms of redox processes for cells with electrodes there is a need to determine the potential of the half-wave E1/2. Finding the half-wave potential is the basis of qualitative analysis of polarographic and voltammetric analyzes. The middle of the area of the abrupt change of current between the two linearly increasing areas of saturation and is the point of the half-wave on the voltammetry. Sometimes it is not possible to reach the possible value of the diffusion current Id and then determining the wave height as the interval from the beginning of the bend of the abrupt section to the last (maximum) point of the characteristic can give an error. Methodology. Since the point of the half-wave E1/2 is the point of bending curve, then on the derivative plot, the potential of the half-wave will correspond to the maximum function. Thus, this feature can be proposed to find the value of E1/2 with voltammetograms. From the proposed algorithm has developed a virtual device based on smoothing and differentiation of data. As a result, the potentials of the half-wave were determined. For the obtained potential value, the corresponding diffusion currents I1/2 were determined. The obtained values of diffusion current depending on the concentration are approximated by an exponential equation in which it is necessary to determine the unknown coefficients: constant multiplier and power factor. By logarithmizing the data, the dependency gets a linear look, which allows you to perform a linear approximation of the data set using the built-in virtual device Linear Fit. As a result, a curve for calibration was plotted according to the approximation equation. The sequence of actions for data linearization, linear approximation, calculation of equation coefficients for calibration and graphical constructions is implemented in the form of a virtual device. Findings. In this work, the algorithm for analyzing the voltammogram is improved: it is proposed to find the value of the half-wave potential E1/2 from the maximum of the graph obtained by graphically differentiating the section of the voltammogram corresponding to the wave. This will allow avoiding errors in determining E1/2 in the absence of the maximum value of the diffusion current Id on the voltammogram. Originality. It is proposed to carry out preliminary data smoothing before graphical differentiation of voltammograms. This makes it possible to avoid ambiguity in determining the inflection point of the characteristic, since the irregularities of the experimental voltammogram will be perceived as the extrema of the function. The best result in this case is obtained by using a low-pass window filter with a window width of three elements. Practical value. A virtual device has been created in the Labview program, which implements the proposed algorithm for determining the potential of the half-wave E1/2 by smoothing and graphical differentiation of the voltammogram. Сonclusions. The virtual instrument in Labview is designed to analyze voltammogram data obtained at various concentrations. The result of data processing is the construction of a curve for calibration.