In a previous blog, the atoms C, H, O, and N were limited to a specific range, 0-50, 0-100, 0-10 and 0-10, respectively. Starting from a wide atom count range ensures molecular formulae are not overlooked. The ranges for the atom count can be restricted further using additional information such as NMR, IR, etc.
A common tactic for elucidating compounds containing nitrogen is to acquire a 15N NMR experiment to assist in setting a narrower range for nitrogen count. The 1H-15N HMBC experiment below indicates the presence of at least 2 nitrogen atoms. Therefore, the nitrogen range can be set to 2-10 atoms and thus reduce the number of candidate molecular formulae.