Amperometric gas detection using a micro-ring electrode coupled with a gas-absorbing droplet

A small gas detector was developed, in which an electrode and a gas absorbe r were combined in a small droplet. An Au film was coated on the outside of a fused-silica capillary, and silicone was covered over the Au film for th e purpose of insulation. The capillary was cut, and then a micro-ring elect rode appeared on its tip. A small droplet was formed at the tip of the capi llary and gas was absorbed into the droplet. The absorbed component was mea sured by the microring electrode that was in contact with the droplet solut ion. In this work, the detection characteristics of the droplet micro-ring electrode were evaluated using SO2 gas. The droplet size was from sub-micro litters to a few micro-litters, and was much smaller than the droplets use d as the gas absorber before. Since the gas-liquid equilibrium was quickly reacted, the measurement could be performed within a short absorbing time. A new absorbing solution was supplied at every measurement, and the electro de could be easily renewed. This system was expected to be suitable for fie ld measurements.