Graphical Ranking of Divisors to Get the Most out of a Resolution-Enhanced Kendrick Mass Defect Plot

Resolution-enhanced Kendrick Mass Defect (KMD) analysis using the new concept of fractional base units (repeating unit R divided by integer X; R/ X as a mathematical moiety) is now a powerful data-processing tool to unravel complex mass spectra of polymers. It enhances regular KMD analysis using the chemical moiety, R, to compute mass defects with unprecedented separation of ion series differing by their isotopic or comonomeric contents, end-groups, or charge states in highly visual KMD plots. The value of the divisor, X, dictates the gain of separating power from the regular to the resolution-enhanced KMD plot, and its choice strongly affects the ease and speed of data interpretation. A simple tool to help select the best values of X depending on the users' needs is mandatory to rationalize the analysis and avoid a time-consuming trial-and-error methodology. We propose two graphical representations intuitively ranking the well-suited divisors for the appropriate separation of isotopes or co-oligomers for copolymeric mass-spectral data. Rankings are extended to any type of data set from homopolymeric blends to terpolymers by generalizing the formulas with three variables beyond the specific separation of isotopes. The RANK functions are now available in commercial or homemade spreadsheets (available upon request) to interactively select divisors and compute the associated KMD plots.