Abstract: An electrochemical method and an electrochemical sensor for breath analysis of single or multiple analytes using a porous, preferably flexible and disposable supporting material is provided, a salt is incorporated, and which can be wetted in contact with the exhaled breath condensate. The electrochemical method acting simultaneously as sampling method, as an electrolyte and as a support for the electrode structures. In some embodiments the salt may be hygroscopic, such that the porous substrate stays wet. To ensure that the obtained signal originates from the analyte, the electrochemical sensor preferably exhibits a differential electrode design, including a sensing (analyte-sensitive) and a blank (analyte-insensitive) electrode in order to isolate and remove the background signals.