e/o = even/odd electrons assuming electron impact ionization
dbr = double bonds and rings

• If the trial formula is C_cH_hO_oN_n then the number of double bonds and rings is (2c-h+n+2)/2.
• [ ] The expected valence for the dbr and e/o calculations is given in the brackets. You can change these values. For example, S can be [2] or [6].
• Rounding for integer mass assumes a resolution of 0.20. That is, 0.81 amu rounds up, but 0.80 rounds down. Check the exact value for the smallest mass peak to be sure.
• Parent mass calculated using the masses of the most abundant isotopes.
• IE Users: To print the spectrum, press [Ctrl]P with the spectrum window active.
• Isotopic abundances from Web-Elements.

T. W. Shattuck, Colby College Chemistry and Los Alamos National Laboratory, 11/19/2000