Fig. 1

The number of molecular formulae as a function of mass tolerance of a mass spectrometer, assuming the element is made from an alphabet of elements C, H, N, O (above) and C, H, N, O, P, S (below), subject to the condition that the number of hydrogens in the formula is less or equal to twice the maximum number of carbon atoms assignable to the formula, and that each formula is at least 25% carbon by mass