Oscillating Chemical Reactions And Analytical Applications

The subject of "nonlinear dynamics" and the phenomenon of oscillating chemical reaction, in particular, have become of great interest across of wide range of scientific research in recent years. Oscillating chemical reactions exhibit exotic behavior and unusual mechanisms. Consequently, they have been considered a useful tool for the determination of trace amounts of chemical compounds. This work develops new methods using oscillating chemical reaction for quantitative analytical determinations of L-valine, rifampicin, and sodium diphenylamine sulfonate for the first time, the accuracy and selectivity of these methods are well-pleasing. The main content consists of four parts:Part Ⅰ. Oscillating chemical reactions and analytical applicationsThis literature review provides a simple introduction to the development of the oscillating chemical reactions, and provides some basic thermodynamic theory related. Mechanisms of some chemical oscillators that were used in analytical determinations are reported in details, especially B-Z chemical oscillation. The research progress in analytical applications from 1978 to 2002 is discussed systematically through representative examples. Part Ⅱ. Effect of sodium diphenylamine sulfonate on the B-Z oscillating chemical reactionThe effects of sodium diphenylamine sulfonate on the B-Z oscillating chemical reaction were studied. Under the conditions of different reactants' concentration, the dependence of the period increase and the amplitude decrease on the injected concentration were reported. Results show that the change of the first oscillation period is directly proportional to the concentration of sodium diphenylamine sulfonate, and all of the related coefficients are greater than 0.9916. Experiments indicated that the variations in concentration of the reactants had an effect on the sensitivity and the accuracy for the determination, especially in the concentration of sulphuric acid. The possible reaction mechanism has been studied.Part Ⅲ. Determnation of rifampicin based on the B-Z oscillating chemicalreaction by the analyte pulse perturbation techniqueThe effect of concentration of rifampicin on the B-Z oscillating reaction and its application in rifampicin quantitative determination were studied. Experiment indicated that rifampicin had an effect on the shape, amplitude and period of the B-Z oscillating wave. The optimum condition and the concentrations of reactants were reported. A linear relationship was observed between the increase in the period of a single oscillation and the rifampicin concentration over the range from 2.49×10-7 to 3.38×10-5M, and the related coefficient is 0.9987 (N=18). The proposed method was used to the determinations of real samples, and the relative standard deviation is less than 5%. Cyclic voltammetry was applied to study the mechanism of the proposed system.Part Ⅳ. Determination of L-valine based on H2O2—CuSO4—KSCN oscillating chemical reactionA new analytical method for the determination of L-valine by the perturbation caused by different amounts of L-valine on the oscillating chemical system, involving the Cu(Ⅱ)-catalysed reaction between hydrogen peroxide and sodium thiocyanate in closed system, is proposed. The method relies on the linear relationship between the changes in the oscillating period and the concentration of L-valine. The calibration curve is linear over the range from 2.77×10-5 to 5.52×10-4 M. The method features good precision (relative standard deviation: 0.83%). Some aspects of the interaction of L-valine with the oscillating chemical system are also discussed.