Determination of paraquat by square-wave voltammetry at a perfluorosulfonated ionomer/clay-modified electrode.

A novel Nafion/clay-modified electrode (NCME) was developed for the determination of paraquat by square-wave cathodic stripping voltammetry. The clay that showed the best performance for the fabrication of the NCME is nontronite (SWa-1, ferruginous smectite). The electrochemical behavior of paraquat showed that the cathodic peak at -0.70 V vs Ag/AgCl permits adequate quantification of the analyte. Linear calibration curves are obtained over the 0-80 ppb range, with a detection limit of 0.5 ppb in pH 8 phosphate buffer solution for 4 min preconcentration time. Various factors influencing the determination of paraquat were thoroughly investigated in this study. The practical analytical utility is illustrated by selective measurements of paraquat in real water samples.