An Organic-Based pH Oscillator

Abstract

In a recent paper, we suggested that the acid-or base-catalyzed dehydration of a hydrated carbonyl compound provides a suitable foundation for an organic-based pH oscillator. Here we present the first experimental example of such an oscillator in a flow reactor, utilizing the base-catalyzed dehydration of methylene glycol as a source of positive feedback (OH -autocatalysis) coupled with the base-catalyzed hydrolysis of gluconolactone for negative feedback (H + production). The large amplitude oscillations (between pH 7 and 10) are reproduced in a kinetic model of the reaction. Such experiments present new possibilities in the design of pH oscillators.

The Transition from pH Waves to Iodine Waves in the Iodate/Sulfite/Thiosulfate Reaction–Diffusion System

“…The study of nonlinear chemical reactions has blossomed in the last three decades, leading to the discovery of numerous chemical oscillators. [1][2][3][4][5][6] These investigations have also made significant contributions towards the understanding of complex phenomena encountered in nature. [7][8][9][10] Among existing chemical oscillators, reaction systems involving sulfur compounds exhibit all kinds of complicated nonlinear behavior due to the existence of multiple oxidation states ranging from À2 to + 6.…”

Four‐Variable Model of an Enzymatic Oscillator Based on Trypsin

“…This analysis shows that the trypsin oscillator behaves in a qualitatively different way as compared to the thiol oscillator and a pH‐based organic oscillator where oscillations emerge through a Hopf bifurcation and end through a saddle‐node bifurcation ,. We did not find any phase plane where the state diagram (one is shown in Figure b) will have a cross‐shape with a bistability region that is characteristic for many oscillatory systems…”

pH Oscillator Stretched in Space but Frozen in Time

“…We fabricated a continuous-flow microfluidic platform where the reactants are first mixed using passive micromixing geometries and thereafter flow through a long (~1 m) and narrow 23 The chip contained four separate inlets labeled A, B, C, and D , and one outlet, O (Fig. 1, and Fig.…”

“…where f j are functions governing the reactions and involve 14 rate constants k i (i = 1-14; see reference 23 for all reactions and rate constants). In the microfluidic chip based on a channel of height 2h and length L, the concentration of each chemical species obeys an advection-diffusionreaction partial differential equation (with constant diffusivity D j ) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 where x and y are the coordinates along and across the channel, and u and v are the corresponding liquid flow velocities, which follow from the Navier-Stokes equations 28 .…”

“…14, 23,29 Another useful characteristic of our microfluidic platform is that the reactant concentrations can be changed controllably in real time without changing the flow rate -this allows for rapid scanning of the oscillator's phase space. In an illustrative example, we supplied four different solutions into the device: sulfite/metabisulfite in inlets A and B with flowrates Q A and Q B (cf.…”