A sensing device including film sensor, a second sensor, and a controller. The film sensor includes a receptor capturing an intended analyte and an unintended analyte in a fluid medium to generate a film sensor signal. The receptor has a receptor cross-sensitivity to the unintended analyte. The second sensor contacts the fluid medium including the intended analyte and the unintended analyte to generate a second sensor signal. The second sensor has a second cross-sensitivity to the unintended analyte different than the receptor cross-sensitivity to the unintended analyte. The controller is programmed to determine a concentration of the intended analyte in the fluid medium in response to the film sensor signal, the receptor cross-sensitivity, the second sensor signal, and the second cross-sensitivity.