Spectrus: Using concentration series to check linearity of integrals in NMR spectra

Description
To validate quantitative NMR conditions, users may record spectra for a series of solutions at different concentrations and check that integrals scale linearly with concentration. Spectrus can facilitate comparison and plotting of integral vs concentration.

Solution

1. Prepare several solutions of a compound (and internal standard if used) at different known concentrations.
2. Acquire 1H NMR spectra for each solution under identical qNMR conditions (relaxation delay, pulse angle, etc.).
3. Process each spectrum in Spectrus (phase and baseline correction).
4. Integrate one or more representative peaks for the analyte and, if applicable, the internal standard.
5. Create a table with:
   • Solution concentration.
   • Corresponding integral (or integral ratio vs standard).
6. Export the table to CSV/Excel and plot integral (or ratio) vs concentration.
7. Evaluate linearity:
   • Assess R² and deviation from the line.
   • Confirm that integrals are proportional to concentration over the working range.
8. Document the validated conditions and any limitations (e.g., linear only up to a certain concentration).