Adduct masses for electrospray mass spectrometry: what to add to the neutral monoisotopic mass, and what to divide by, to predict an observed m/z. Useful in reverse too, for identifying an unexpected peak as sodium rather than a product.
| Adduct | Polarity | Charge | M multiplier | Mass shift (Da) |
|---|---|---|---|---|
| [M+H]+ | Positive | 1 | 1 | +1.0073 |
| [M+Na]+ | Positive | 1 | 1 | +22.9892 |
| [M+K]+ | Positive | 1 | 1 | +38.9632 |
| [M+NH4]+ | Positive | 1 | 1 | +18.0332 |
| [M+2H]2+ | Positive | 2 | 1 | +2.0146 |
| [M+H-H2O]+ | Positive | 1 | 1 | -17.0033 |
| [2M+H]+ | Positive | 1 | 2 | +1.0073 |
| [M-H]- | Negative | 1 | 1 | -1.0073 |
| [M+Cl]- | Negative | 1 | 1 | +34.9694 |
| [M+HCOO]- | Negative | 1 | 1 | +44.9987 |
| [M-2H]2- | Negative | 2 | 1 | -2.0146 |
Conventional ESI adduct set; proton and electron masses from CODATA.
These values are imported from the same data the Aliquot calculators use, so this page cannot drift away from what the tools compute.