A method of mass spectrometry is disclosed comprising digitising a first signal output from an ion detector to produce a first digitised signal, detecting one or more peaks in the first digitised signal and determining a first area S0 or a first intensity I0 of the one or more peaks and a first arrival time T0 of the one or more peaks thereby forming a first list of data pairs and determining whether or not the first area S0 or the first intensity I0 exceeds a first threshold area Smax or a first threshold intensity Imax. The first threshold area Smax and the first threshold intensity Imax correspond respectively to a peak area and a peak intensity indicative of substantially simultaneous arrival of two ions which the ion detector is unable to resolve. If it is determined that the first area S0 or the first intensity I0 does not exceed the first threshold area Smax or the first threshold intensity I0 then the method further comprises including the first area S0 or the first intensity I0 and/or the first arrival time T0 or data derived from the first area S0 or the first intensity I0 and/or the first arrival time T0 in a first histogram.