The development of a thick-film electrochemical sensor and instrumentation for in-situ determination of carbon dioxide partial pressure (pCO2) in the marine environment

Describes the development of a fast-response amperometric sensor for recording in-situ measurements of carbon dioxide partial pressure (pCO₂) in the oceans. Carbon dioxide diffuses through a membrane, lowering the pH of the internal electrolyte. This causes a metal complex to dissociate; the increase in uncomplexed metal ion is detected by voltammetry. The innovation in this design is achieved by printing polymeric thick film electrodes (Au, Pt, Ag/AgCl) onto porous substrates. Careful design to minimize iR drop and electrode capacitance allows transient voltammetric techniques to be used (scan rates up to 1 V/s), whilst still keeping the working electrode close to the membrane to ensure a fast response, thereby giving improved sensitivity and precision over conventional amperometric sensors. Analogue electronics are combined with microcontroller-based digital signal processing to increase the signal-to-noise ratio. Data can be processed and stored in the microcontroller´s memory, allowing the instrument to be deployed remotely (for example on databuoys or underwater vehicles)