Screen-printed zeolite-modified carbon electrodes

The evaluation of screen-printed carbon electrodes modified with zeolites f or the determination of the herbicides paraquat and diquat is described and compared to the corresponding zeolite-modified carbon paste electrodes. Cy clic voltammetry was used to characterise the electrochemical behaviour of paraquat at both electrodes, indicating better defined peaks for the screen -printed electrodes than for the corresponding carbon pastes and lesser inf luence of residual oxygen. Square wave voltammetry was then applied to inve stigate the partitioning of this herbicide into the zeolite particles (Y-ty pe) to the conductive composites. The screen-printed zeolite-modified elect rode (SPZME) resulted in faster accumulation and release of the electroacti ve probe compared to the zeolite-modified carbon paste electrode (ZMCPE). T he improved response time, sensitivity, and reproducibility, were attribute d to the thin film structure of SPZME compared to the bulky ZMCPE. Substant ial enhancement of current signal was observed when operating with disposab le SPZMEs that were not soaked in any electrolyte solution prior to the acc umulation step. The selective accumulation of paraquat over diquat was demo nstrated by using ZSM-5 zeolite particles, while its strong binding to the aluminosilicate prevented efficient voltammetric detection.