Spectrus: Using isotopic labeling experiments to support structural assignment in xC/UV/MS data

Description
Isotopic labeling (e.g., ²H, ¹³C, ¹⁵N) can shift specific ions in MS spectra and clarify which atoms participate in fragments. Spectrus can compare labeled vs unlabeled spectra to support detailed structural interpretation.

Solution

1. Acquire xC/UV/MS data for both:
   • The unlabeled compound.
   • The corresponding isotopically labeled analog (same method and conditions).
2. Import both datasets into the same Spectrus project.
3. For each component, compare MS and MS/MS spectra:
   • Identify peaks that shift by the expected mass increment corresponding to the label.
4. Map shifts:
   • Peaks that shift indicate fragments containing the label.
   • Unshifted peaks indicate fragments that do not contain the labeled position.
5. Use this pattern to:
   • Refine fragmentation schemes.
   • Confirm or exclude candidate structures for fragments.
6. Document labeled vs unlabeled comparisons in your interpretation report to justify structural conclusions.