Determination of analytes using electrochemically active indicator species as reactants

A method for determination of the concentration of an analyte in a solution, comprising:

• providing a sample of the solution comprising the analyte, wherein the analyte is selected from the group consisting of:
• chlorine, iron (VI), and carbon dioxide;
• adding to the solution a molar excess of an electrochemically and chemically oxidizable indicator species which forms an oxidized species when contacted by the analyte, wherein the oxidizable indicator species is selected from the group consisting of:
• N, N-Diethyl-p-phenylenediamine (DPD), N,N-bis(2,4-di-sulfobenzyl)toluidinetetrasodium salt (SBT), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS);
• allowing the indicator species to be chemically oxidized by the analyte to provide an oxidized indicator species;
• measuring, using spectroscopy, a signal corresponding to the oxidized indicator species after chemical oxidization thereof by the analyte;
• electrochemically oxidizing the indicator species at a chosen voltage for a selected time period, whereby a first electrochemical oxidation charge is passed;
• recording the first electrochemical oxidation charge;
• measuring, using spectroscopy, a signal corresponding to the oxidized indicator species after the step of electrochemically oxidizing the indicator species;
• repeating the step of electrochemically oxidizing the indicator species at least a second time, whereby at least one second oxidation charge is passed;
• recording the at least one second electrochemical oxidation charge;
• and
• measuring, using spectroscopy, a signal corresponding to the oxidized indicator species after the step of electrochemically oxidizing the indicator species at least a second time,
• whereby the concentration of the analyte is determined using the measured signals corresponding to the oxidized indicator species and the electrochemical oxidation charges.