Ethyl acetate (EA) and formaldehyde (FA) imprinted polymers produced by porogen and template imprinting, respectively. The sensors were produced by coating a QCM device with imprinted polymer (polyurethane, PU, or methacrylic acid-co-ethylene glycol dimethacrylate, McE), followed by coating with gold nanoparticles, and finally with a second layer of MIP. The change of resonance frequency (Δf) was then monitored in the presence of different gaseous compounds in dry air. Studies with interferents (right) were performed with 25 ppm analyte, or 50% relative humidity in the case of water. Reproduced with permission [44].