Ferrocene-enhanced polyvinyl chloride-coated electrode for the potentiometric detection of total residual chlorine in simulated ballast water

• An all-solid ion-selective sensor based on PVC-coated glassy carbon was fabricated.
• Addition of ferrocene can greatly improve the performance of the electrode.
• The respond and failure mechanisms of the electrode are discussed.
• This electrode is promising for detecting total residual chlorine in electrolytically treated ballast water.

In-situ electrolytic generation of chlorine is commercially adopted as an economic and effective method for treating ballast water (BW). An in-situ and rapid method for detecting total residual chlorine (TRC) is necessary for automatic control on the electrolysis. A polymer-coated electrode fabricated by coating a glassy carbon (GC) electrode with a polyvinyl chloride (PVC) coating that contains zephiran chloride (ZephCl) was prepared in this study. This all-solid ion-selective sensor was used to detect TRC in the simulated electrolytically treated BW. Results showed that adding ferrocene (Fc) in the PVC coating could significantly improve the response speed, reproducibility and stability of the electrode. The potential of the Fc–PVC–ZephCl–GC electrode was linearly proportional to the logarithm of TRC within the range of 1 mg/L to 20 mg/L. The interference of the dissolved oxygen and the possible co-existing ions in seawater was also evaluated without evident interference found. The response mechanism of the electrode, the enhancement of Fc and the failure mechanism of the electrode were discussed. The Fc–PVC–ZephCl–GC electrode could be used as a suitable sensor for the in-situ monitoring of TRC in the electrolytic treatment of BW.