What is Mass Resolution?
Mass resolution is a measure of how well mass peak profiles with similar masses can be separated from each other. The “10% valley” definition of mass resolution cited for double focusing mass spectrometers is as follows. For two mass peak profiles of equal ion abundance with a minimum between them of 10% of the maximum profile height, the mass resolution is their average mass divided by the mass difference between them. In the figure, the tails of two profiles overlap at 5% of the profile maxima to provide a 10% valley between the two profiles. Mass peak profiles become narrower as the mass resolution increases, which is why separation of the profiles occurs. In the example below, three ions with m/z ratios of 281 were separated using a mass resolution of 5000. Each ion is from a compound from a different source: an ever-present calibrant ion (steady signal), the coating within a gas chromatograph column (gradually increasing signal in concert with the temperature ramp within the oven)
