Oscillating Chemical Reaction And Its Application In The Analytical Determination

The subjects of nonequilibum and nonlinear are very usual in the field of science. They have attracted the attention of researches for many years. One important investigation is that of chemical oscillation. There has been a focus on the theoretical and experimental chemical kinetics in recent years. Studies of oscillating chemical reactions are in two major aspects; (a) Application of regular chemical oscillation to analytical determination and (b) designing new oscillating chemical reactions and elucidating the intricate underlying mechanisms of them. This work report the oscillating chemical reaction involving tyrosine in details and develops new methods using oscillating chemical reaction for quantitative analytical determination of hydroquinone and caffeine, the results are satisfied. The main content consists of four parts.PART I: Oscillating Chemical reaction and its application in theanalytical chemistryThis part describes the basic thermodynamic theory of oscillating chemical reaction and introduces several usual oscillating chemical reactions and their mechanisms in details. The whole history of the application of oscillating chemical reactions in the analytical chemistry is also reviewed. And the perspective of oscillating chemical reactions is discussed to the point.PART II: Kinetic Determination of Hydroquinone by Belousov-Zhabotinskii Oscillating Chemical ReactionA novel and convenient method with good selectivity and high sensitivity for the determination of hydroquinone (HQ) based on the Belousov-Zhabotinskii (B-Z) oscillating chemical reaction has been presented The optimum condition for the determination has also been investigated, In the B-Z reaction system, when the sample was injected, the change of the amplitude is linearly proportional to the logarithm of theconcentration of HQ in the range 2.0×10-4-1.0×10-2 M (r=0.9965), whereas the concentration of HQ is over the range from 4.0×10-7-2.5×10-4 M, the calibration curve fits a second-order polynomial equation very well (r=0.9983).PART in: A Novel Chemical Oscillator with Tyrosine as the SubstrateA new oscillating chemical reaction system involving the manganese (II)-catalyzed reaction among potassium bromate, acetone and tyrosine in acidic medium was described in this paper. The apparent activation energy of the induction period (Ein) and that of oscillation period (Ep) were calculated, Ein=110.61KJ/mol, Ep=159.41KJ/mol. The optimum concentration of each reactant was investigated and a steady oscillating chemical system was obtained. The influence of temperature was studied as well. The mechanism of the reaction was also explored in detail and a possible quantitative explanation was proposed.PART IV: Determination of Caffeine Using Oscillating ChemicalReaction in a CSTRA new analytical method for the determination of caffeine by the sequential perturbation caused by different amounts of caffeine on the oscillating chemical system involving the manganese(II)-catalysed reaction between potassium bromate and tyrosine in acidic medium in a CSTR was proposed. The method exposed for the first time in this work. It relies on the relationship between the changes in the oscillation amplitude of the chemical system and the concentration of caffeine. The calibration curve fits a second-order polynomial equation very well when the concentration of caffeine over the range 4.0×10-6 to 1.2×10-4 M (r=0.9968). The effects of influential variables were studied. Some aspects of the potential mechanism of action of caffeine on the oscillating chemical system were also discussed.