Method of mass spectrometry and a mass spectrometer

A method of mass spectrometry comprising the steps of

• providing a sample;
• producing a set of fragment ions by:
• exciting a spot in a first area on the surface of the sample to produce a set of parent analyte ions;
• determining the ion mobility of at least some of the ions from the set of parent analyte ions;
• fragmenting at least a portion of the set of parent analyte ions to produce a set of fragment ions;
• determining the mass to charge ratio of at least some of the ions from the set of fragmented ions as a function of ion mobility;
• performing the method of producing a set of fragmented ions for at least a second area of the sample;
• performing a method of relating at least two fragment ions to one another, comprising the steps of:
• associating the set of fragment ions produced from the first area with the set of fragment ions produced from the second area, as a function of the ion mobility of the set of parent analyte ions from the first and second areas;
• and
• identifying changes between the quantity of a fragment ions in the first area and at least the second area.

A mass spectrometer comprising:

• an excitation means for exciting a sample to produce parent analyte ions;
• an ion mobility separator for receiving parent analyte ions and to separate the ions according to their ion mobility;
• a collision cell for receiving the parent analyte ions from the ion mobility separator and to fragment at least a portion of them into fragment ions;
• a Time of Flight analyser for receiving the parent analyte ions and fragment ions from the collision cell and produce data relating to their time of flight through the analyser;
• and
• processing means for associating the fragment ions with the parent analyte ions by comparison of the ion mobility of the parent analyte ions with the ion mobility of the ions of the parent ions associated with the fragment ions and further for assigning at least one fragment ion to a parent analyte ion by identifying changes in the quantity of a parent analyte ion in different areas of the sample and identifying corresponding changes in the quantity of at least one fragment ion in the different areas of the sample.