Collision induced dissociation study of 10 monoterpenes for identification in trace gas measurements using the newly developed proton-transfer reaction ion trap mass spectrometer

We present the study of fragmentation patterns of different monoterpene species after dissociative proton-transfer and after collision induced dissociation (CID) in a newly developed proton-transfer reaction ion trap mass spectrometer (PIT-MS). For the monoterpene measurements the proton-transfer reaction chamber was set at an E/N-value of 90–100 Td; at this value the monoterpenes can be found at m/z values of 137 and 81. CID patterns of all 10 monoterpenes studied are found to be distinguishable, making it possible to positively identify a monoterpene solely on the basis of its CID pattern. However, identification of compounds in a mixture of several monoterpenes will still be difficult. Additionally, we find that the outcome of a CID experiment, expressed in the ratio between different fragments, depends on the kinetic energy of the ions as they exit the drift tube. This behavior is attributed to differences in ion internal energy at different drift tube voltages. The effect of ion internal energy change on the CID pattern is shown when the cooling time between isolation and dissociation of the parent ions is changed, and the CID fragmentation ratio of fragments 95 and 81 amu of α-terpinene is affected.