New All-Solid-State Carbonate Ion-selective Electrode With Ag₂CO₃/BaCO₃ As Sensitive Films:Its Preparation And Application

Carbonate anions (CO32-) as the important variable determine the pH value of the water. The measurement of the CO32-is also of great significance in various fields such as fishery breeding, industrial producing, environmental monitoring and physiological analysis. All-solid-state ion-selective electrodes (ISEs) have been developed for determining multiple ions, including CO32-, the use of all-solid-state ISEs features the following advantages:highly sensitive, small size, short response time and sample-free treatment. A new all-solid-state carbonate ISE was fabricated through electrochemical and ion-exchange reactions with nano-Ag particles and Ag2CO3/BaCO3 as ion-to-electron transducer and ion-selective layer, respectively. This paper presents the corresponding chemical reaction principles involved, the detailed procedures for construction of the electrode and the applications of the electrode in various experiments. The fabricated electrode was characterized through scanning electron microscope, energy dispersive spectrometer, and electrochemical analyses. The electrode was further used to measure CO32-concentration in boiler water.Electrochemical methods and ion-exchange reactions were used to deposit nano-Ag and Ag2CO3/BaCO3 composite onto the surface of the basal Ag, using silver nitrate, sodium carbonate and barium hydroxide octahydrate. The main process parameters such as the nano-Ag electroplating time, sweep segments of cyclic voltammetry, scan rate, electrolyte concentration and the ion-exchange reaction time duration reveal different impacts on the characteristics of the coatings. The optimum condition was 5 min for nano-Ag electroplating process, two sweep segments,50 mV/s-250 mV/s for scan rate,1% by wt.-5% by wt. for Na2CO3 concentration and 30 min-90 min for Ba(OH)2-bearing ion-exchange reaction.The optimized electrode exhibited stable linear responses to CO32-(10-5 mol/L 10-1 mol/L), and the average slope of the curve was-25.85 mV/decade and the detection limit of 1.0×10-5 mol/L (R2≥0.99). And the electrode showed negligible responses to NO3-, SO42-, and Sal- anions. The electrode was further used to measure CO32-concentration in boiler water. The measured concentration was lower than that determined through titration. Overall, the electrode was characterized by miniaturized size, robust construction, and compatibility with other equipment and thus could be ideally integrated into various sensor platforms to for in situ real-time monitoring.