Gas sensor with first and second electrodes and a reagent for binding the target gas

A gas sensor for determining a quantity of target ions in a sample by sensing a target gas, the gas sensor comprising:

• first and second electrodes;
• a support layer between the first and second electrodes;
• a reagent on the support layer for binding the target gas and a container for receiving the sample;
• wherein the first and second electrodes are in electrical contact with the support layer and the reagent;
• wherein the container is fluidically connected to the first and second electrodes;
• wherein the container contains or is fluidically connected to the reagent for converting the target ions in the sample into the target gas;
• wherein an inside of the container and gas sensor are sealed;
• wherein the first and second electrodes are in a headspace of the container;
• wherein the support layer is not in direct contact with the sample;
• and
• wherein the first and second electrodes are configured to measure an electrical impedance of the support layer.