Mass spectrometry controls

Abstract

The Invention provides a method of immunopurifying and characterising an analyte from a sample comprising: (i) providing a predetermined amount of a control substance bound to a substrate via a linkage cleavable by acidic pH and/or reducing agents and optionally additional analyte specific antibodies or fragments thereof bound to a substrate, wherein the control substance is specific for the analyte or is not specific for the analyte; (ii) allowing analyte when present in the sample to bind to the control substance or said optional additional analyte-specific antibodies or fragments, wherein the control substance bound to the substrate (i) may be provided after contacting the analyte with the optional additional analyte-specific antibodies (ii); (iii) washing unbound material away from the substrate; (iv) acid eluting the analyte bound thereto, from at least one substrate; (v) performing mass spectrometry to identify two or more peaks, at least one peak of which is associated with the presence of the analyte and at least a second peak which is associated with at least a portion of the control substance; and (vi) comparing the size or intensity of the second peak to a predetermined calibration value to allow the first peak associated with the analyte to be calibrated.