The Nitrate Chemical Ionisation Mass Spectrometer incorporates the APi-ToF, however with the addition of a chemical ionisation unit attached before the APi. In contrast to the APi-ToF, in the Nitrate-CIMS the clustering of the NO3- ions with molecules in the sample flow allows the detection of molecules which were present in an uncharged state in the atmosphere as well as ions. Aside from the chemical ionisation unit, the operating principal is the same as the APi-TOF. The chemical ionisation unit used in our group is produced by Airmodus.