I have been trying to measure extracellular hydrogen peroxide in basic MEM using electrochemical means. I have been inducing a mimetic state of hypoxia using cobalt chloride hexahydrate and have been struggling to assess the quantity of hydrogen peroxide in my sample. I have ran a calibration using my cobalt standard in blank MEM, spiking with H2O2 and measuring via amperometry. I have found that a cathodic spike/ peak occurs but does not step like classic amperometric measurements. The change in current almost immediately returns to baseline.
I am under the assumption that this may be due to the peroxide acting as a catalyst to CoCl2, and the peroxide is being oxidised. Can someone either confirm or shed some light on this issue.
Regards.
Dear Craig,
Electrochemical quantification of hydrogen peroxide in an aqueous solution containing cobalt chloride is indeed possible and has been demonstrated in the following study:
Journal of Solid State Electrochemistry
April 2010, Volume 14, Issue 4, pp 621–631
Carbon paste electrode modified by cobalt ions dispersed into poly (N-methylaniline) preparing in the presence of SDS: application in electrocatalytic oxidation of hydrogen peroxide
Reza Ojani, Jahan-Bakhsh Raoof, Banafsheh Norouzi
Abstract
Conducting and stable poly (N-methylaniline) film was prepared by using the repeated potential cycling technique in aqueous solution containing N-methylaniline, sulfuric acid, and sodium dodecyl sulfate (SDS) at the surface of carbon paste electrode (CPE). The transition metal ions of Co(ІІ) were incorporated to the polymer by immersion of the modified electrode in 0.1 M cobalt chloride solution for 10 min. The electrochemical characterization of this modified electrode exhibits stable redox behavior of Co(ІІ)→Co(ІІІ) and formation of insoluble oxide/hydroxide cobalt species on the CPE surface. The modified electrode showed well-defined and stable redox couples in alkaline aqueous solution. The modified electrode showed excellent electrocatalytic activity for oxidation of hydrogen peroxide. The response of modified electrode toward the H2O2 oxidation was examined using cyclic voltammetry, differential pulse voltammetry, square wave voltammetry, and chronoamperometry. This modified electrode has many advantages such as simple preparation procedure, good reproducibility, and high catalytic activity toward the hydrogen peroxide oxidation. Such characteristics were explored for the specific determination of hydrogen peroxide in cosmetics product sample, giving results in excellent agreement with those obtained by standard method.
http://link.springer.com/article/10.1007/s10008-009-0824-3
Hoping this will be helpful,
Rafik
Dear Craig,
It depends on the applied potential in you cell. You might want to change to an applied potential at which H2O2 is reduced but not the Co. In case that this is not possible, you might try to modify your WE in order to make it selective for H2O2.
I hope this helps, for more detailed help you need to share more details of your experimental set-up.
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