Electrochemical detection of free chlorine at inkjet printed silver electrodes

• Low-cost, reliable and sensitive electrochemical method for free chlorine analysis
• First time usage of inkjet printing strategy for free chlorine sensor development
• Detection limit of 2 ppm with a sensitivity of 30 μC/ppm
• Detection mechanism proposed based on HR-SEM and XPS results
• Methodology validated by analysis of swimming water and commercial disinfectant

A low-cost, reliable and sensitive electrochemical method for free chlorine analysis in water using inkjet printed silver electrodes is presented. Free chlorine detection was based on linear sweep voltammetry (LSV) analysis of AgCl/Ag2O films formed over an inkjet printed silver electrode by the spontaneous reaction between silver and free chlorine species (i.e. HClO and ClO−) present in solution. The formation of AgCl/Ag2O films was studied and characterized by high resolution scanning electron microscopy (HR SEM) and X-ray photoelectron spectroscopy (XPS) techniques. LSV characterization demonstrated a quantitative linear relationship between the amount of AgCl/Ag2O formed and the concentration of free chlorine in water within a range from 1 to 100 ppm. After optimization of several parameters (e.g. scan rate, reaction time, starting potential), lowest detectable free chlorine concentration was 0.4 ppm (by standard addition method), while the limit of detection (S/N = 3) was equal to 2 ppm, with a sensitivity of 30 μC/ppm. The validation of the proposed methodology was performed by comparison with the standard N,N-diethylparaphenylenediamine (DPD) method for analyzing swimming pool water samples. Finally, it was demonstrated that reproducible and disposable silver electrodes could be easily prepared by inkjet printing in a large scale and in any required geometry to fit on-line and on-site free chlorine analyses requirements.

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