Time shift for improved ion mobility spectrometry or separation digitisation

摘要

A method of analysing ions comprises separating ions according to a physico-chemical property in a separator 3 (e.g. ion mobility separator), transmitting the emerging ions to a transfer device 4 (e.g. travelling wave ion guide), and energising a pusher electrode to obtain data. The transit time or drift time through the transfer device 4 is repeatedly switched between a first transit time t1 for obtaining first data and a second longer transit time t2 for obtaining second data. The increase in transit time t2-t1 is equal to half the pusher electrode repetition period t3 (i.e. half a time bin). The first and second data are combined to form a composite data set which may have a higher digitisation rate. By repeatedly time shifting or delaying a portion of the ions sampled by an orthogonal acceleration time-of-flight mass analyser 5, the invention seeks to improve the sampling rate of separation peaks without increasing the pusher electrode frequency or reducing a time-of-flight analyser cycle time.