Patent ID: 8822914

Claim:
A method of screening a sample for a presence of one or more known compounds of interest comprising: providing a mass spectrometer comprising a fragmentation device and a mass analyser; repeatedly switching said fragmentation device between a first mode of operation and a second mode of operation, wherein in said first mode of operation parent ions are not substantially fragmented within said fragmentation device or are arranged to bypass said fragmentation device and are then subsequently mass analysed by said mass analyser and wherein in said second mode of operation parent ions are substantially fragmented within said fragmentation device to form a plurality of fragment ions which are then subsequently mass analysed by said mass analyser; determining if a candidate parent ion of interest is present in a first data set obtained when said fragmentation device was operated in said first mode of operation; and determining if one or more corresponding fragment ions of interest are present in a second data set obtained immediately before or after said first data set; wherein if said candidate parent ion of interest is determined to be present in said first data set and one or more corresponding fragment ions of interest are also determined to be present in said second data set then said method further comprises determining whether or not said candidate parent ion of interest and said one or more fragment ions of interest have substantially similar elution or retention times or ion mobility drift times; wherein if said candidate parent ion of interest and said one or more fragment ions of interest are determined to have substantially similar elution or retention times or ion mobility drift times then a determination is made that a known compound of interest is present in said sample.