Mass Spectrometry m/z Calculator
Calculate m/z Ratio
m/z = (M ± n×H) / z for ESI
Molecular Weight from m/z
Calculate MW from observed m/z peak
Charge State Envelope
Calculate m/z for multiple charge states
Mass Accuracy (ppm)
Calculate mass accuracy in ppm
Formula
m/z = (M + zH)/z (positive ESI) | MW = m/z × z - z × 1.00728 | ppm = ((obs - theo)/theo) × 10⁶
Frequently Asked Questions
What is m/z in mass spectrometry?
m/z (mass-to-charge ratio) is the fundamental measurement in mass spectrometry. It represents the mass of an ion divided by its charge number. For singly charged ions (z=1), m/z equals the molecular mass plus or minus a proton.
How do I calculate molecular weight from ESI mass spectra?
For positive ESI: MW = (m/z × z) - z × 1.00728 (proton mass). For multiply-charged ions, use two adjacent peaks: MW = z₂(m/z₂ - 1.008) where z₂ = (m/z₁ - 1.008)/(m/z₁ - m/z₂).
What is mass accuracy in ppm?
Mass accuracy (ppm) = ((observed - theoretical) / theoretical) × 10⁶. High-resolution instruments (Orbitrap, FTICR) achieve <5 ppm, while TOF instruments typically achieve 5-20 ppm.
You may also need
A
Molar Mass Calculator
Free molar mass calculator. Calculate the molecular weight of chemical compounds from their formula. Supports common elements and parenthetical groups.
ScienceA
Percent Composition Calculator
Free percent composition calculator. Calculate the mass percentage of each element in a chemical compound.
ScienceA
Avogadro's Number Calculator
Free Avogadro's number calculator. Convert between moles and number of particles (atoms, molecules, ions). Uses Nₐ = 6.022 × 10²³.
Science