A New pH Sensor Based on a Glassy Carbon Electrode Coated with a Co/Al Layered Double Hydroxide

A glassy carbon electrode has been coated by electrodeposition with a thin film of cobalt based layered double hydroxide (LDH) and used as a pH sensor. The developed electrode displays a linear super-Nernstian response (-76.2 +/- 0.6 mV/pH) in the pH range between 2 and 14 and it is particularly suitable to operate in strongly alkaline solution. The reproducibility of the sensor construction is good with a relative standard deviation of the calibration curve slopes of +/- 2.5% (n=4). The electrode has a response time comparable to that exhibited by commercial glass electrodes in the pH range examined and is not affected by interference from the most common anions and cations.