In one embodiment, a method for detecting contaminants in a liquid comprises: contacting a sensor with a liquid, generating electrical information based upon a concentration of the contaminant in the liquid, transmitting the electrical information to a controller, and determining the concentration of a contaminant in the liquid. The sensor can comprise a film, a purge chamber, and a transducer, which are configured such that a first surface of the film is in fluid communication with the liquid and the purge chamber is in fluid communication with a second surface of the film that is opposite the first surface, and wherein the transducer is in fluid communication with the purge chamber.