Technical report on chemical sensors performance

The report will present an overview of sensors that are useful for the study of seeps, and present a detailed comparison of commercial and prototype CO2 and pH sensors. CO2 sensors: 1) Severinghaus CO2 sensors (Microelectrodes ltd), 2) the HydroC-­‐CO2 logger sensor (CONTROS GmbH), 3) the “GasPro-­‐pCO2” (developed by the team coordinated by Prof. S. Lombardi; Sapienza -­‐ University of Rome-­‐CERI), 4) the MuFo (Multifiber Optode logger, developed in this project in a collaboration between Prof. I. Klimant University Graz and the MPI-­‐MM). pH sensors: 1) glass electrodes Microelectrodes ltd), 2) optodes (developed in this project in a collaboration between Prof. I. Klimant University Graz and the MPI-­‐MM), 3) SeaFET (ion-­‐selective field-­‐effect transistor, Satlantic)

Highly Sensitive Poisoning-Resistant Optical Carbon Dioxide Sensors for Environmental Monitoring

A new optical carbon dioxide sensor for environmental monitoring is presented. It combines a robust and long-term stable sensing material with a compact read-out device. The sensing material relies on a NIR pH indicator immobilized into ethyl cellulose along with a quaternary ammonium base. The perfluorinated polymer Hyflon AD 60 used as a protection layer significantly enhances the long-term and mechanical stability of the sensor foils, as well as the robustness against poisoning gases, e.g. hydrogen sulfide. The sensor can be stored under ambient conditions for more than six weeks, whereas sensors covered with silicone rubber deteriorate within one week under the same conditions. The complete sensor device is applicable after a three-point (re)calibration without a preconditioning step. The carbon dioxide production and consumption of the water plant Egeria densa was measured in the laboratory. Furthermore, results of profiling carbon dioxide measurements during a research cruise on the Baltic Sea at water depths up to 225 m are presented