Figure 5From: Metabolomic database annotations via query of elemental compositions: Mass accuracy is insufficient even at less than 1 ppmThe isotopic abundances of the M+1 and M+2 ions can be used to filter molecular formula candidates. This example shows isotopic abundance pattern for silylated sorbitol. The red circle shows a 5% region with the correct target. All other formulae can be excluded if the mass spectrometer has a 5% error (RMS) on isotopic abundances.Back to article page