Determination pH of aqueous solutions using solid-state sensor based on a thin film of cobalt oxide nanoparticles electrodeposited on carbon ceramic electrode

In this paper a solid-state pH sensor is proposed based on cobalt oxide nanoparticles electrodeposited on carbon ceramic electrode. The morphology of carbon ceramic electrode coated with cobalt oxide nanoparticles was studied by scanning electron microscopy (SEM). It showed that the particles were deposited in nano size and uniformly on electrode surface. The modified electrode showed Nernstian behavior with a slope of 74.04 mV/pH in the wide pH range of 1.5 – 12. The ion selectivity of the pH sensor with respect to Li+, Na+ and K+ were tested and the values of -11.9, -12.4 and -12.1 were obtained for 〖log K〗_(H^+,〖Li〗^+)^pot, 〖log K〗_(H^+,〖Na〗^+)^pot and 〖log K〗_(H^+,K^+)^pot, respectively. Some important parameters including repeatability, reproducibility, and response time of the sensor were studied. In order to evaluate the applicability of the sensor a number of acid–base titrations were done. Also, in order to evaluate the efficiency of the sensor for measuring the pH in complex matrixes some real samples were tested. Comparing statistical results of modified electrode with a glass pH electrode by using t-test indicated that there is no significant difference in concerning accuracy. The obtained results were in good agreement with a conventional glass pH electrode.