Using PEDOT Film Modified Electrode to Monitor Iodide and Its Enhancement of Arsenite Sensing

Iodide was investigated using poly(3,4-ethylenedioxythiophene)/glassy carbon electrode (PEDOT/GCE) as an monitoring tool. When this electrode was scanned to the positive potential (+0.7 V) in the presence of 6x10-3 M, the redox couple was gradually separated into two redox couples involving the iodide/triiodide and triiodide/iodine redox processes due to the iodide doping behavior occurs easily with the sufficient positive potential and the higher iodide concentration. The I2-PEDOT may be the doping result and it lowers the activation energy of iodide redox processes. The PEDOT/GCE shows linear current response (Ipa(mA) = 21.553[KI](M) + 8.2602, R2 = 0.9995, S/N = 3) to iodide. Through the iodide mediator, PEDOT/GCE can determine As(III) with a sensitivity of 303.3 μA mM-1 cm-2. Particularly, it can enhance the current response for As(III) by increasing the iodide molar ratio. The current ratio of IAs(III)/II- was about 1.66 amplification when molar ratio of nI-/nAs(III) was 0.3.