Free Isotope Pattern Calculator
Estimate the M+1 and M+2 peak intensities relative to the monoisotopic peak from the molecular formula.
M+1 Relative Intensity
12.07 %
M+1 Relative Intensity vs Number of Carbons
Isotope Pattern Estimation
The natural isotope distribution creates characteristic patterns in mass spectra. The M+1 and M+2 peaks relative to the monoisotopic (M) peak help identify molecular formulas.
Approximate Rules
M+1 contributions per atom: C = 1.1%, H = 0.015%, N = 0.37%, O = 0.04%, S = 0.8%
M+2 contributions: O = 0.20% each, S = 4.4% each, plus (M+1)²/200
These are approximations. Accurate patterns require full combinatorial calculation, especially for chlorine and bromine-containing compounds.
Example Calculation
Estimate isotope pattern for C10H14N2O3.
- 01M+1 = 10×1.1 + 14×0.015 + 2×0.37 + 3×0.04 = 11.0 + 0.21 + 0.74 + 0.12 = 12.07%
- 02M+2 = 12.07²/200 + 3×0.20 = 0.73 + 0.60 = 1.33%
Frequently Asked Questions
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