Highly sensitive CNT composite amperometric sensors integrated in an automated flow system for the determination of free chlorine in waters

We report the benefit of using an optimized composite electrode, based on a multiwall carbon nanotubes and epoxy resin, as working electrode in an automated flow system. The optimal composite electrode composition consists in a 10% carbon nanotubes and 90% epoxy resin. This composition provides lower limit of detection and increases the stability and reproducibility of the analytical signal compared to the 20% conventional composition electrodes. Moreover, the standard solutions are on-line prepared with an automated flow system. The integration of the developed carbon nanotube electrodes in the proposed flow system provides a highly sensitive analyzer for free chlorine determination in water down to the 20 μg L−1. The working range was found to be 0.02–4 mg L−1 with an analysis time of 60 s. The system sensitivity was maintained into the control limits (±2σ) for one month, with a mean value of −0.146 (±0.008) μA L mg−1. Validation of the analytical system has been performed by the successful determination of free chlorine in tap water and swimming pools water samples.