In traditional GC-MS/MS analysis, the technique that is most often utilized is electron ionization (EI). However in some cases, compounds can be labile and fragment heavily when using EI, which can make it difficult to identify them via NIST library searches or to generate selective MRMs. Chemical ionization (CI) operated in both positive and negative ion modes can help reduce the fragmentation significantly. In CI ions are produced via collisions with the reagent gas (e.g. methane, ammonia, or isobutane). By utilizing the dedicated CI ionization source available on the Xevo TQ-GC, which was designed for extended robustness and rapid tool-free changeover, both EI and CI experiments can be performed on the same system.
Switching between EI and CI on the Xevo TQ-GC is very simple, no tools required, and the changeover takes less than 10 min.