Calculadora de Assimetria de Pico
Calcule o fator de assimetria de picos cromatográficos para avaliar a qualidade da separação.
Asymmetry Factor (As)
1.200
Asymmetry Factor (As) vs Back Half-Width at 10% Height (B)
Formula
Peak Asymmetry and Tailing Factor
Peak shape is a critical quality attribute in chromatography. Asymmetric peaks indicate column problems or unwanted secondary interactions.
Formulas
Asymmetry Factor: As = B / A (measured at 10% height)
USP Tailing Factor: Tf = (A + B) / (2A) (measured at 5% height, but often approximated at 10%)
Exemplo Resolvido
A peak with front half-width A = 5 mm and back half-width B = 6 mm at 10% height.
- 01As = 6 / 5 = 1.200
- 02Tf = (5 + 6) / (2 × 5) = 11 / 10 = 1.100
- 03Slight tailing (acceptable; As < 1.5 is typically OK)
Perguntas Frequentes
What asymmetry values are acceptable?
Typically As between 0.8 and 1.5. USP requires Tf <= 2.0 for most methods. Values outside 0.8-1.2 suggest column or method issues that should be investigated.
What causes peak tailing?
Secondary interactions with free silanols (for reversed-phase), extra-column dead volumes, column degradation, and chemical equilibria (e.g., acid-base) at the analyte concentration. Adding buffer or using end-capped columns helps.
What causes peak fronting?
Column overload (too much sample injected), very strong solute-stationary phase interactions at high concentrations, or a thermodynamically unfavorable isotherm shape.
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