Enter your Molecular Formula, Charge, Adduct Type, and Instrument Resolution into the Mass Spectrometry Calculator to get the Theoretical m/z, Exact Mass, and Mass Error. Plug in your Observed m/z and Minimum Abundance to see how closely your experimental data matches the predicted values.
Theoretical m/z
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Exact Mass
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Mass Error
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Mass Error (Da)
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The m/z ratio is the mass-to-charge ratio of an ion, which is the fundamental measurement in mass spectrometry. It represents the mass of the ion divided by its charge state.
Mass error in ppm is calculated as: ((observed m/z - theoretical m/z) / theoretical m/z) × 1,000,000. It measures the accuracy of mass measurements.
Adducts are ions formed when molecules associate with other species like protons (H+), sodium (Na+), or potassium (K+) during ionization. Common positive adducts include [M+H]+, [M+Na]+, and [M+K]+.
Multiple peaks occur due to isotopes of the same element having different masses. For example, carbon-13 creates additional peaks alongside the main carbon-12 peak.
Exact mass is the precise mass of a molecule calculated using exact atomic masses of specific isotopes. Molecular weight is the average mass considering natural isotope abundances.
Higher resolution instruments (like FT-ICR) can distinguish between very close m/z values and provide more accurate mass measurements compared to lower resolution instruments (like quadrupoles).
Use standard chemical notation like C6H12O6 for glucose or H2SO4 for sulfuric acid. Include all atoms with their counts, and use capital letters for element symbols.