Screen-printed zeolite-modified carbon electrodes

The evaluation of screen-printed carbon electrodes modified with zeolites for the determination of the herbicides paraquat and diquat is described and compared to the corresponding zeolite-modified carbon paste electrodes. Cyclic 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 influence of residual oxygen. Square wave voltammetry was then applied to investigate the partitioning of this herbicide into the zeolite particles (Y-type) to the conductive composites. The screen-printed zeolite-modified electrode (SPZME) resulted in faster accumulation and release of the electroactive probe compared to the zeolite-modified carbon paste electrode (ZMCPE). The improved response time, sensitivity, and reproducibility, were attributed to the thin film structure of SPZME compared to the bulky ZMCPE. Substantial enhancement of current signal was observed when operating with disposable SPZMEs that were not soaked in any electrolyte solution prior to the accumulation step. The selective accumulation of paraquat over diquat was demonstrated by using ZSM-5 zeolite particles, while its strong binding to the aluminosilicate prevented efficient voltammetric detection.