Calculadora de Fator de Retenção
Calcule o fator de retenção em cromatografia para caracterizar a interação com a fase estacionária.
Retention Factor (k')
3.250
Retention Factor (k') vs Retention Time (tR)
Formula
## Retention Factor (Capacity Factor) The retention factor k' describes how strongly a compound is retained by the stationary phase relative to the mobile phase. ### Formula **k' = (tR - t0) / t0** where tR is the retention time of the analyte and t0 is the void (dead) time. Ideal k' values are 2-10. Below 1, peaks elute near the void and separation is poor. Above 20, peaks are broad and run time is long.
Exemplo Resolvido
A peak at tR = 8.5 min with void time t0 = 2.0 min.
- 01k' = (8.5 - 2.0) / 2.0 = 6.5 / 2.0 = 3.25
- 02The compound spends 3.25 times more time in the stationary phase than the mobile phase.
Perguntas Frequentes
What is an ideal retention factor?
For most HPLC separations, k' between 2 and 10 gives the best balance of resolution and analysis time. For GC, k' of 5-20 is common.
How is void time measured?
Inject an unretained compound (e.g., uracil for reversed-phase HPLC, or methane for GC). Its retention time is the void time t0.
How does k' relate to resolution?
Resolution increases with k' but with diminishing returns. The factor k'/(1+k') in the resolution equation approaches 1 for large k'. Beyond k' = 10, increasing retention helps little but wastes time.
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