Detection of nitrite using poly(3,4-ethylenedioxythiophene) modified SPCEs

The poly(3,4-ethylenedioxythiophene) (PEDOT)- and PEDOT/multi-wall carbon nanotubes- (PEDOT/MWCNTs) modified screen-printed carbon electrodes (SPCEs) were fabricated and their catalytic properties towards nitrite were studied. Due to the electrostatic interaction between the negatively-charged nitrite ions and the positively-charged PEDOT film, the operating potential for nitrite oxidation was shifted about 160 mV to negative side, compared to bare SPCE, as a PEDOT film was deposited on the SPCE. The diffusion coefficient obtained from RDE experiment is 2.05×10^-5 cm² s^-1. The electron transfer coefficient (α) was increased from 0.515 to 0.615 as the sensing electrode was changed from PEDOT-modified to PEDOT/MWCNTs-modified electrode. Therefore, PEDOT/MWCNTs composite shows the superior catalytic property towards nitrite and the operating potential was further shifted about 100 mV to the negative side. The sensitivity and limit of detection (LOD) for the PEDOT- and PEDOT/MWCNTs-modified SPCEs are about 100 mA cm^-2 M^-1, 1.72 μM and 140 mA cm^-2 M^-1, 0.96 μM, respectively. The possible interferences from several common ions were tested. The developed sensor was also applied to the determination of nitrite concentration in tap water sample.