Die Erfindung betrifft Vorrichtungen und Verfahren zum Nachweisen eines Analyten.The device has a sensor chamber (30) with a sensor for detecting an analyte in a transportation medium, and an analyte testing chamber (40) receiving the analyte in the medium. A distributor (20) has a circular duct with four ports spaced apart from each other. The distributor has an adjustable barrier between two adjacent ports. A controller controls the distributor such that the medium is led by the distributor without passing from the testing chamber into sensor chamber to wash the medium, and the medium is led by passing from the testing chamber into sensor chamber to measure the medium.
