Determination of Cl-, Br-, I-, Mn2+, malonic acid and quercetin by perturbation of a non-equilibrium stationary state in the Bray-Liebhafsky reaction

A new method applying a non-linear chemical system under conditions far fro m thermodynamic equilibrium in microvolume/microconcentration quantitative analysis is described. The chemical system used as a matrix is the Bray-Lie bhafsky reaction in a non-equilibrium stationary state close to a bifurcati on point. The method is based on monitoring the response of this system to perturbations by Cl-, Br-, I-, Mn2+, malonic acid and quercetin analyte sol utions, which are followed potentiometrically either by an Ag+/S2- ion-sens itive or by a Pt electrode. A linear response of the potential shift versus the logarithm of the analyte concentrations is found in the following rang es: 1.3 X 10(-6) mol dm(-3) less than or equal to [Cl-] less than or equal to 1.6 X 10(-4) mol dm(-3), 1.0 X 10(-6) mol dm(-3) less than or equal to [ Br-] less than or equal to 8.3 X 10(-5) mol dm(-3), 2.0 X 10(-6) mol dm(-3) less than or equal to [I-] less than or equal to 1.0 X 10(-4) mol dm(-3), 8.4 X 10(-7) mol dm(-3) less than or equal to [Mn2+] less than or equal to 8.3 X 10(-5) mol dm(-3), 3.8 X 10(-7) mol dm(-3) less than or equal to [mal onic acid] less than or equal to 2.1 X 10(-5) mol dm(-3) and 1.5 X 10(-8) m ol dm(-3) less than or equal to [quercetin] less than or equal to 3.7 X 10( -5) mol dm(-3). Under the investigated conditions an improved detection lim it for all halides tested is obtained. Unknown concentrations of the analyt es can be determined from a standard series of calibration curves to an acc uracy within +/-5%. In addition, the application of potentiometric measurem ents in microvolume/microconcentration quantitative analysis is diversified .