A new sensor based on oxidative combustion of nitroaromatics to NO(2) and its detection with a quartz crystal microbalance (QCM) coated with copper phthalocyanine (CuPc) was developed for determination of nitroaromatics in landfill gas. An alternative method based on gas chromatography-mass spectrometry (GC-MS) was also used in order to assess the performance of the proposed method. The results show that the analytical apparatus based on the QCM is less expensive than the GC-MS, and that the analytical error is 0.8% for both methods.