Resolution (Chromatography) Calculator Formula
Understand the math behind the resolution (chromatography) calculator. Each variable explained with a worked example.
Formulas Used
Resolution (Rs)
resolution = 2 * abs(tr2 - tr1) / (w1 + w2)Variables
| Variable | Description | Default |
|---|---|---|
tr1 | Retention Time Peak 1 (tR1)(min) | 5.2 |
tr2 | Retention Time Peak 2 (tR2)(min) | 5.8 |
w1 | Peak Width at Base 1 (w1)(min) | 0.3 |
w2 | Peak Width at Base 2 (w2)(min) | 0.35 |
How It Works
Chromatographic Resolution
Resolution quantifies how well two adjacent peaks are separated. It combines the effects of selectivity, efficiency, and retention.
Formula
Rs = 2 × (tR2 - tR1) / (w1 + w2)
where tR is retention time and w is peak width at the base (4-sigma width for Gaussian peaks).
Worked Example
Two peaks at 5.2 and 5.8 min with base widths of 0.30 and 0.35 min.
- 01Rs = 2 × (5.8 - 5.2) / (0.30 + 0.35)
- 02Rs = 2 × 0.6 / 0.65 = 1.2 / 0.65 = 1.846
- 03Baseline separation achieved (Rs > 1.5)
Frequently Asked Questions
What resolution is needed for quantitation?
Rs >= 1.5 (baseline separation) is required for accurate quantitation. For screening purposes, Rs >= 1.0 may suffice. Pharmacopeial methods often require Rs >= 2.0.
How can I improve resolution?
Three approaches: increase selectivity (change mobile phase, stationary phase, or temperature), increase efficiency (use longer column or smaller particles), or increase retention (change mobile phase strength). Selectivity changes are most effective.
How does resolution scale with column length?
Rs is proportional to sqrt(N), where N is the plate count. Doubling the column length doubles N but only improves Rs by sqrt(2) = 1.41×. This also doubles run time and back pressure.
Ready to run the numbers?
Open Resolution (Chromatography) Calculator