CE50: quantifying collision induced dissociation energy for small molecule characterization and identification.

Survival yield analysis is routinely used in mass spectroscopy as a tool for assessing precursor ion stability and internal energy. Because ion internal energy and decomposition reaction rates are dependent on chemical structure, we reasoned that survival yield curves should be compound-specific and therefore useful for chemical identification. In this study, a quantitative approach for analyzing the correlation between survival yield and collision energy was developed and validated. This method is based on determining the collision energy (CE) at which the survival yield is 50% (CE(50)) and, further, provides slope and intercept values for each survival yield curve. In initial experiments using a defined set of homologous compounds, we found that CE(50) values were easily determined, quantitative, highly reproducible, and could discriminate between structural and even positional isomers. Further analysis demonstrated that CE(50) values were independent of cone potential and orthogonal to compound mass. Experimentally determined CE(50) values for a diverse set of 54 compounds were correlated to Molconn molecular structure descriptors. The resulting model yielded a statistically significant linear correlation between experimental and calculated CE(50) values and identified several structural characteristics related to precursor ion stability and fragmentation mechanism. Thus, the CE(50) is a promising method for compound identification and discrimination.