Design and evaluation of a Hg(II) sensor based on the response of a poly(3,4-ethylenedioxythiophene) modified electrode

Abstract

The electro-synthesis of poly(3,4-ethylenedioxythiophene), PEDOT, has been widely studied due to its different and important applications. Considering that one of the most important electrochemical characteristics of this polymer is its ability to undergo p- and n-doping/undoping, our research group has tested its potential usefulness for cations extraction based on the n-doping/undoping process, hitherto almost unexplored. Therefore, in a first stage, EDOT was electropolymerized on AISI 316 stainless steel, SS, and the SS|PEDOT modified electrode was then obtained. Applying the n-doping potential to these SS|PEDOT electrodes immersed in Hg(II) solution at physiological pH (PBS) it was verified that the cation was incorporated into the polymeric matrix and, depending on the area of the working electrode and removal method (n-doping/undoping), its quantitative extraction was possible. It was also found that the charge recorded during the process is proportional to Hg(II) concentration, hence the assembly is now proposed as sensor for this cation. To this end, in the current paper the amperometric response of the SS|PEDOT electrode toward Hg(II) in PBS, prepared under the optimum conditions previously established and described, was studied. First of all, it is noteworthy establishing that the response obtained with a freshly prepared SS|PEDOT electrode prior to each measurement is highly reproducible. Having this in mind, the modified electrode can be thought as a sensor that may be utilized as a disposable device. Once the electrode response was optimized, analytical parameters were established, namely linear response between 66.6 μmol·L-1-1.0 mmol·L-1Hg(II), 1s response time, and quantification and detection limit 10 and 15 μmol·L-1, respectively. It is possible thus to have at our disposal a suitable and inexpensive sensor that would enable quick and economical quantification of this toxic element using electrochemical methods.