Spectrus: Referencing chemical shifts to a standard (TMS or solvent)

Description
Accurate chemical shift referencing is important for comparing spectra and reporting assignments. Spectra are usually referenced to TMS (0 ppm) or to residual solvent peaks with known positions.

Solution

1. Identify the reference signal:
   • TMS at 0.00 ppm, if present.
   • Otherwise, a known residual solvent peak (e.g., CHCl3 at 7.26 ppm in CDCl3).
2. Use the manual Reference function and click on the reference peak:
   • Enter the correct chemical shift value for that peak.
   • Apply the reference; all peaks in the spectrum will shift accordingly.
3. Verify that other known peaks (e.g., solvent multiplets, internal standards) now appear close to their expected positions.
4. Perform assignments and generate reports based on the referenced spectrum.