Gold/gold oxide as a solid state on-chip pH sensing probe for food applications

In this work we investigate Gold/gold oxide as a solid-state ultra-micro pH sensor for monitoring of different foods which are, typically between 3.5–7 in pH. Using cyclic voltammetry, a linear shift in the gold oxide reduction peak voltage was observed, in response to changes in pH of a solution in which the sensor was submerged. The sensor also has very low sample volume requirements down to ∼100 µL. Sensors gave a super-Nernstian response of -67.7 mV/pH in the pH range of pH 3 to pH 7 with an accuracy of <0.02 of pH units. Their high sensitivity, low hysteresis and minimal interferene by common interferents demonstrate that these electrodes can be utilised as pH sensors for real world application. A maximum deviation of 0.29 pH units between the developed metal-oxide pH sensor and a conventional glass electrode indicates good usability for beverage samples.