Belousov Zhabotinskii Research Articles

Kinetic determination of hydroquinone by a Belousov–Zhabotinskii oscillating chemical reaction

A 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 the concentration of HQ in the range 1.0×10 −2–2.0×10 −4 M ( r=0.9965), whereas, when the concentration of HQ is over the range from 2.5×10 −4 to 4.0×10 −7 M, the calibration curve fits a second-order polynomial equation very well ( r=0.9983).

Periodic, Mixed-Mode, and Chaotic Regimes in the Belousov–Zhabotinskii Reaction Catalyzed by Ferroin

The periodic, mixed-mode, and chaotic regimes in the ferroin-catalyzed Belousov–Zhabotinskii (BZ) reaction observed in a continuous stirred tank reactor (CSTR) reactor at various flow rates were experimentally studied. It was found that an increase in the flow rate resulted in the appearance of various complex oscillations. The possibility of the numerical simulation of experimentally observed asymptotic mixed-mode oscillations and chaotic regimes with the use of a kinetic scheme that includes experimental rate constants of each step of the ferroin-catalyzed BZ reaction was first demonstrated. The reaction scheme adequately describes the bifurcation sequence of experimentally observed oscillating regimes.

Several types of oscillations in Belousov–Zhabotinskii reactions with amino acids as organic substrates

AbstractUnder batch‐reactor conditions, 7 amino acids were employed as organic substrates in Belousov–Zhabotinskii (BZ) oscillations. These amino acids displayed different types of oscillations. Aspartic acid exhibited the classical BZ oscillations owing to the formation of oxalacetic acid (an intermediate of Aspartic acid oxidation) which is easily brominated. Tyrosine exhibited the uncatalyzed BZ oscillations where the metal ion catalyst is not necessary. Cystine, alanine, glycine, and glutamic acid could give rise to sustained oscillations only in the presence of acetone as a coupled organic substrate to remove bromine via bromination, known as the mixed‐substrate BZ oscillations. Serine showed oscillations even in the absence of acetone though serine is not subjected to bromination. Obviously, this is a new kind of BZ type oscillations since no bromination occurred at all. The excess bromine is possibly removed through the reduction by serine and/or its intermediates. Addition of acetone induces the dual‐frequency oscillations. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 405–410, 2002

Effect of Manganese(II) Ions on Regular Self-Oscillations in the Belousov–Zhabotinskii Reaction in a Tank Reactor with Constant Stirring

The effect of manganese(II) ions on the asymptotically regular self-oscillation regime of the Belousov–Zhabotinskii reaction, catalysed by ferroin, in a tank reactor with constant stirring has been studied. An increase in the manganese(II) ion concentration in the system leads to an increase in the period of the self-oscillations. The sensitivity of the self-oscillation of the chemical reaction on the addition of Mn2+ ions is decreased with an increase in acidity. To explain the results obtained we have used a reversible Oregonator model, which is supplemented with reactions between manganese(II) and manganese(III) ions and bromoxyl radicals, malonic acid, and ferroin.

Traveling Wavefronts for Delayed Reaction-Diffusion Systems via a Fixed Point Theorem

By using Schauder's fixed point theorem, we prove some existence results for traveling wavefronts of reaction-diffusion systems with quasimonotonicity reactions. More precisely, we reduce the existence of traveling wavefronts to the existence of an admissible pair of supersolution and subsolution which are easy to construct in practice. Finally, to illustrate our main results, we study the existence of traveling wavefronts for a delayed predator-prey model with diffusion as well as the reaction-diffusion system with the well-known Belousov–Zhabotinskii reaction, and the obtained results improve the existing ones.

Traveling Wave Fronts of Reaction-Diffusion Systems with Delay

This paper deals with the existence of traveling wave front solutions of reaction-diffusion systems with delay. A monotone iteration scheme is established for the corresponding wave system. If the reaction term satisfies the so-called quasimonotonicity condition, it is shown that the iteration converges to a solution of the wave system, provided that the initial function for the iteration is chosen to be an upper solution and is from the profile set. For systems with certain nonquasimonotone reaction terms, a convergence result is also obtained by further restricting the initial functions of the iteration and using a non-standard ordering of the profile set. Applications are made to the delayed Fishery–KPP equation with a nonmonotone delayed reaction term and to the delayed system of the Belousov–Zhabotinskii reaction model.

Determination of traces of thallium using the transient chaotic regime in the Belousov–Zhabotinskii oscillating chemical reaction

New method is developed for the determination of traces (<10 −9 M) of thallium(I) in aqueous solutions. The method is based on an effect of thallium(I) ions on transient chaotic regimes in the Belousov–Zhabotinskii oscillating chemical reaction. The optimum conditions for the determination has been determined. The detection limit is ≤10 −12 M. There are few interferences at low concentrations.

Experimental study of the dynamics of spiral pairs in light-sensitive Belousov–Zhabotinskii media using an open-gel reactor

Within an open-gel reactor we study the interaction of spiral waves in a light-sensitive Belousov–Zhabotinskii (BZ) medium by varying the applied light intensity which controls the local excitation threshold. A small, initially symmetric pair of counter-rotating spiral waves after several rotation periods undergoes a symmetry-breaking instability. For a spiral wave interacting virtually with its mirror image on the opposite side of a plane boundary impermeable to diffusion, we measure the drift along the boundary as a function of the applied light intensity. The experimental data are compared with the results of numerical simulations obtained from a modified Oregonator model.

Determination of riboflavin by the perturbation of active oxygen on a chemical oscillating reaction

This paper studies the perturbation of active oxygen (O 2 −→H 2O 2) produced from the irradiated riboflavin on a chemical oscillating reaction, and a new and sensitive methodological approach for the determination of riboflavin is proposed based on it. An automatic experimental setup is designed to combine the irradiation of riboflavin with the analogous Belousov–Zhabotinskii reaction, which is implemented in a continuous-flow stirred tank reactor (CSTR). The oscillator of Mn (II)-catalyzed reaction between diacetone and potassium bromate in acidic medium is used to evaluate the perturbation effect. The presence of active oxygen inhibits the oscillation and results in a longer oscillating periods. The change of the oscillating period is linearly proportional to the concentration of riboflavin over the range 6.5×10 −9∼1.2×10 −7 mol/l, with a detecting limit of 2.4×10 −9 mol/l. Potential and spectrophotometric methods are used to monitor the reaction. Influence of experimental variables on the perturbation is investigated and the possible mechanism of the action of active oxygen on the oscillating system is discussed.

Determination of gases (NO, CO, Cl 2) using mixed-mode regimes in the Belousov–Zhabotinskii oscillating chemical reaction

We show a principle possibility of the determination of gases concentrations (NO, CO, Cl 2) by their affect on mixed-mode oscillations in the Belousov–Zhabotinskii (BZ) oscillating chemical reaction. These oscillations are characterized by single large amplitude oscillation followed by a number of small amplitude oscillations. The method of the determination is based on a construction of a calibration plot given by the dependence of the number of small amplitude oscillations on gas concentration.

Applicability of the Homotopy Method to the determination of fixed points in chemical kinetics models

Reducing the complex chemical kinetics is an important challenge to implement chemical schemes in a turbulent combustion code. An important step in the reduction of chemical kinetics is to extract the fixed points of the set of differential equations associated with the chemical scheme since they are useful to determine the low manifolds which may be used to reduce kinetic mechanisms. This paper aims at testing a potentially powerful method, namely the Homotopy Method, for extracting fixed points from nonlinear dynamical systems. The method is tested on a 3D and a 7D model of the well-known Belousov–Zhabotinskii reaction. This study shows that the Homotopy Method has a significantly better efficiency than available Newton–Raphson algorithms but that the stiffness of the chemical kinetics equations still resists this method when the number of species increases.

Potential of the analyte pulse perturbation technique for the determination of polyphenols based on the Belousov–Zhabotinskii reaction

This paper introduces the use of the analyte pulse perturbation technique to the Belousov–Zhabotinskii reaction, developed in a continuous-flow stirred-tank reactor, in quantitative oscillating reaction-based determinations. This straightforward, expeditious approach was tested on the kinetic determination of various polyphenols (hydroquinone, catechol, resorcinol, pyrogallol and gallic acid) by their perturbation on the oscillating reaction. The proposed method relies on the relationship between changes in the oscillation amplitude of the chemical system and the analyte concentration, which is revealed for the first time in this work. The dynamic range is between 0.3–6.0 μmol and the method features good precision (RSD ca. 2%) and excellent throughput (60 samples h−1); the latter is a result of the expeditiousness with which regular oscillations are regained after each perturbation. The potential mechanism of action of polyphenols on the oscillating system is discussed.

Effect of Methyl Ketones in the Belousov−Zhabotinskii Reaction

When a methyl ketone is added to the Belousov−Zhabotinskii (BZ) reaction, an increase of the induction period and in the number of oscillations is observed. This behavior can be explained by the competition of malonic acid and the methyl ketone for molecular bromine. We studied the effect of four methyl ketones in the BZ reaction and found a direct relationship between the induction period, the concentration, and the enolization constant of the ketone. A discussion of the results with regard to the crucial concentration of bromomalonic acid is given. The experimental results are supported by simulations based upon the GTF mechanism of the reaction.

Hysteresis in entropy production in a model chemical reaction exhibiting subcritical Hopf bifurcation

In the reversible Oregonator, a model exhibiting oscillations in the Belousov–Zhabotinskii reaction, a bistability in the entropy production (free energy dissipation) between a steady state and an oscillatory state is reported in the neighborhood of a subcritical Hopf bifurcation. We identified this region in the past by a perturbation method. The numerical results present a thermodynamic formulation of multistable structures in a nonlinear dissipative system.

Static and swinging chemical waves in a two-interface dynamics on a ring

An existing scaling model of a reaction–diffusion system is extended to a circular trajectory. The equations describe the evolution of a slow (X) and a fast (Y) concentration variable. The fast variable jumps between extreme values across a reaction interface as the rate parameter becomes very large. The model is reduced to one equation for the dynamics of the smooth (slow) variable while the Y-jumps occur at two interfaces spatially located on a ring. The equation is solved subject to 2π-periodicity conditions on the ring and continuity conditions at the interfaces. Both static (with zero velocity) and moving (with velocity v) wave solutions are found. An analogy is then drawn between our reaction–diffusion system and oscillating chemical reactions such as the Belousov–Zhabotinskii (BZ) reagent, confined to a torus-shaped container. A toroidal thin tube with a very small diameter could simulate the ring geometry. The conjectured waves capture the oscillations of the catalyst (ferroin), with the maxima and minima corresponding to the ferroin and ferriin, spatial domains in the doughnut, respectively. The non-stationary wave solutions predict a migration of those domains yielding swinging (back and forth) patterns along the ring. The azimuthal position of the interfaces exhibits temporal oscillations. Thus these simulations suggest interesting experiments on spatio–temporal patterns in excitable chemical media in annular reactors.

Dynamical Patterns in Arrays of Coupled Chemical Oscillators and Excitators

Dynamical regimes arising due to mutual interactions of oscillatory and excitatory modes of the Belousov−Zhabotinskii (BZ) reaction in a two-array and linear and circular three-arrays (with different arrangements of intrinsic connections) of identical continuous stirred tank reactors (CSTRs) coupled via symmetric passive diffusion/convection mass exchange were studied both experimentally and by numerical simulations. The coupling strength among individual CSTRs and the threshold of excitability of the BZ reaction mixture were varied systematically. Firing numbers (vectors) were used for classification of observed oscillatory−excitatory modes. Full spectra of firing numbers ranging from 0 to 1 were detected in all CSTR arrays investigated in experiments. The numbers of oscillators and excitators, threshold of excitability, and the way of coupling and coupling strengths within the array are principal factors affecting firing patterns of the array. Numerical simulations with the dimensionless three-variable Oregonator based model of the BZ reaction predict qualitatively well dynamical regimes encountered in experiments. Noisy coupling among the individual CSTRs due to hydrodynamical fluctuations is suggested to explain some of the observed differences.

Belousov-Zhabotinskii type oscillations with amino acids or peptides as organic substrates in the presence of Mn2+ and Fe(phen)32+ as coupled catalysts

Nine amino acids, aspartic acid, glycine, serine, tyrosine, alanine, glutamic acid, threonine, cystine, phenylalanine, and two peptides, and two peptides, glycine-glycine peptide, glutamic acid-cystine-glycine peptide, give rise to damped oscillations of the Belousov–Zhabotinskii(BZ) type in a batch reactor. Both Mn2+ and Fe(phen)32 are essential for most of those oscillations; and the oscillations in [Mn3+] and [Fe(phen)33+] are also observed. The role of two metallic ions played in the oscillations are analyzed, showing that Mn2+ catalyzes the oxidation of the amino acids or peptides by BrO3− to produce some intermediates which effectively reduce Br2 to Br− catalyzed by Fe(phen)32+. © 1998 John Wiley & Sons, Inc. Int. J. Chem Kinet 30: 243–247, 1998.

Critical ReviewApproaching the use of oscillating reactions for analytical monitoring

Introduction Physico-chemical features of oscillating chemical reactions involved in chemical analysis Belousov–Zhabotinskii reaction Copper oscillators Peroxidase–oxidase biochemical oscillators Oscillating reactions in analytical determinations Analytical use of the Belousov–Zhabotinskii reaction Determination of metal ions Determination of inorganic anions Determinations based on chaotic regimes Analyte pulse perturbation technique Validation in the analysis of real samples Conclusions References

Synchronization of Oscillations and Propagation of Excitations in Circular and Linear Arrays of Coupled CSTRs

Synchronizations of oscillatory regimes of the Belousov−Zhabotinskii (BZ) reaction in a circular array of three identical CSTRs coupled via symmetric passive diffusion/convection mass transfer were studied experimentally. Stability of symmetric and asymmetric phase-shifted oscillatory regimes with respect to variations of the coupling strength among the reaction cells was examined. The all-in-phase regime was found to be the only regime stable over the entire range of coupling strength values. Phase-shifted oscillatory regimes were found to be stable only within a narrow interval of very low coupling strength values. Spontaneous transitions of the phase-shifted regimes to the synchronized mode due to stochastic fluctuations of the coupling strength were observed. Numerical simulations with the four-variable Oregonator based model of the BZ reaction qualitatively confirmed the experimental findings. Propagation of an excitable response to periodic pulsed stimulations in a linear three-array of coupled chem...

A Completely Inorganic BZ-Type Oscillator in a Closed Homogeneous System

Abstract In a batch reactor, an absolutely homogeneous inorganic Belousov–Zhabotinskii (BZ)-type oscillator has been designed in the system of BrO3−–H2PO2−–Mn2+–Fe(phen)32+–H2SO4. The oscillations of both [Br−] and [Mn3+]/[Mn2+] as well as [Fe(phen)33+]/[Fe(phen)32+] were observed by monitoring the changes of either the potential on a bromide electrode or the absorbance at the maximum absorbance wavelength for Mn3+ and Fe(phen)33+, respectively. Both of those two metallic ions are essential in the present system to give rise to the oscillations; their roles in the oscillation are discussed. It is found that Mn2+ can not be replaced by other substances, while Fe(phen)32+ can be replaced by either N2 flow or acetone. However, it can not be replaced by other metallic ions, including Mn2+ and Ce3+. Those results suggest that Mn2+ is the real oscillating catalyst for an autocatalytic formation of HBrO2 and Fe(phen)32+ is a catalyst for the catalytic reduction of Br2 by H2PO2− to remove any excess Br2 produced during the oscillations.