Fragmentation Resilience Energy Mass Spectrometry (FREMS): Methods Validation and Compound Differentiation

Fragmentation Resilience Energy Mass Spectrometry (FREMS) builds on the field of energy-resolved mass spectrometry and previously used methods, e.g., Survival Yield. It exploits breakdown energies at near "continuous" ramp (0.2% NCE increments) to offer higher resolution and a reliable method for compound differentiation, contaminant identification and structural elucidation. Implementation of FREMS involves acquiring ion breakdown/formation curves as collision energy is incrementally increased. These curves themselves can be analyzed by several means to give a single metric-Fragmentation Resilience (FR₅₀). This value has been shown to be experimentally interchangeable with the modified-Survival Yield (m-SY₅₀) and the Cross-Intersect (C-I). A full panel of testing on an LTQ-Orbitrap revealed that breakdown energies depend only on three controllable parameters-number of ions inside the ion trap, Maximum Inject time and Activation Time. A fairly linear relationship (R² > 0.95) with proposed FR₅₀, m-SY₅₀ and C-I metrics provides reliable adjustment mechanisms for these variables via calibrations. Consequently, this technique can be applied to ions produced by any atmospheric pressure ionization processes and treated as exclusively in vacuo experiments. Applications of FREMS to 4-chlorobenzylpyridinium ion revealed that under collisional activated dissociation (CAD) conditions, the rate of decomposition of precursor ion is equivalent to the rate of formation of its fragments, i.e., normalized breakdown and formation curves intersect at inflection points.