Calculadora de Precisão de Massa — Formula

Mass Accuracy in Mass Spectrometry

Mass accuracy is the difference between the measured and theoretical mass of an ion, expressed in parts per million (ppm). It determines how confidently you can assign a molecular formula.

Formula

Error (ppm) = (m_measured - m_theoretical) / m_theoretical × 10⁶

Modern high-resolution instruments achieve < 2 ppm (Orbitrap) or < 1 ppm (FT-ICR). Time-of-flight (TOF) instruments typically achieve 2-5 ppm.

Exemplo Resolvido

Glucose [M+H]+ measured at 180.0637, theoretical 180.0634.

  1. Error = (180.0637 - 180.0634) / 180.0634 × 10⁶
  2. Error = 0.0003 / 180.0634 × 10⁶ = 1.67 ppm
  3. Error in mDa = 0.3 mDa