Investigation On Theory, Instrument And Overlapped Incisions Resolution Method Of Oscillographic Analysis And Their Application

Oscillographic analysis is an electro analytical chemistry field founded by Pro. Gao. This thesis is concerned with the problems that oscillographic analysis maintained in theory, instrument, resolving overlapped incisions and some other aspects. In this study, the theory formula of pulse current oscillographic chronopotentiometry and that of endpoint potential of small oscillogram were deduced. A virtual oscillographic chronopotentiometry analysis system based on LabVIEW was constructed and a new method for resolving overlapped incisions was presented. This study was significant in perfecting ocsillographic theory and instrument, resolving overlapped incisions of ocsillogram, enlarging the application of ocsillographic analysis, and further enriching the study content of electroanalytical chemistry. The thesis is divided into five chapters and the main work of author was described as follows,1. The theory formula of pulse current oscillographic chronopotentiometry was deduced. When the duty ratio of pulse alternate current applied over the cell has changed, the length ratio of cathodic branch of oscillogram to anodic one would be altered, which lead to the change of the ratio of the Faraday current to charging current and also the sensitivity of the incisions on the cathodic or anodic branch. Using the theory formula, the phenomena above can be explained.The author with his coworkers proposed two types of small oscillogram, Hg-R₁ and R₂-K. The adjustment method of the R₂-K. type small oscillogram was investigated and oscillographic chronopotentiometry based on small oscillogram was established. The research results showed that when the small oscillogram was used to oscillographic detection, three features would be obtained. Firstly, at the smaller potential window oscillogram, better oscillogram stability and smaller interference caused by coexisted substances can be acquired. Secondly, the determination at the small oscillogram would be more sensitive than the classic oscillogram for the fact that smaller alternate current was needed. Finally, the i₀/i₁ ratio of small ocsillogram changed along with the alteration of the type of small ocsillogram. The i₀/|i₁| of R₂-K type small ocsillogram is smaller than the classic one while the i₀/|i₁| of Hg-R₁ type small ocsillogram is bigger than the classic one, so the effect of direct current in oscillographic chronopotentiometry is manifested. Thus, the theory of the oscillographic analysis is developed.2. Based on virtual instrument technique, a virtual oscillographic analysis system was constructed using Labview software. The performance of the system was tested by the oscillographic chronopotentiometry with high and low frequency current and ocsillographic behavior of dopamine and adrenaline. The study indicate that this system have the ability of real-time analysis and computation, controlled data collection and wave display, magnanimity data storage, etc. Studies of this system make oscillographic chronopotentiometry with high and low frequency current (HL-OCP) and other oscillogaphic methods real applicable analysis method.3. Wavelet transform and Fourier transform were combined in processing frequency domain signals. Fourier deconvolution method (FWTL-FSD) of approximations obtained from frequency domain wavelet transform as linear function and that (FWTLD-FSD) of different approximations obtained from frequency domain wavelet transform as devoiced signals and linear function were presented and used in processing overlapped incisions and overlapped chromatographic peak signals. It shows that the overlapped incision depth of dE/dt-t curve increased obviously after resolution. Which indicates the methods can improve the determination limit and sensitivity of ascillographic muticomponent analysis. The result of resolving the overlapped HPLC peaks show all the signal peaks can achieve baseline separation. FWTLD-FSD method can be applied in resolving noisy signals with signal-to-noise ratio higher than 5, but a little inferior to FWTL-FSD method in sensitivity. Compared with classical FSD, the two novel method both exhibits some advantages such as good overlapped peak resolution, simple operation without selection procedure of the linear function.4. The resolution of overlapped incisions and overlapped chromatographic peak signals were processed by means of chemometric methods include partial least squares (PLS), principal component regression (PCR) and Radial basis function networks (RBFN). The comparing research of multivariate calibration of ocsillographic and chromatographic electrochemical signals was carried out contemporarily. From the research, it can be indicated that RBAN model exhibits much better resolution ability than PLS and PCR in resolving overlapped OCP incisions as well as overlapped HL-OCP incisions; but to chromatographic electrochemical overlapped peak signals, PLS and PCR model have better effects. It can be draw out that resolution method with linear mapping ablitiy such as PLS, PCR is more adequate for resolving chromatographic electrochemical overlapped peak signals (concentration, area) with linear mapping characteristics; For oscillographic overlapped incisions of two components study system presenting nonlinear mapping relation mainly, resolution method with nonlinear mapping ability, such as RBAN, can carry out good results.During the study of doctor's candidate, author has completed and published 13 papers.