Patent ID: 8383420

Claim:
A method for equilibrating an isotope dilution mass spectrometry sample, comprising the steps of: a) adding to a solid phase carrier selected from the group consisting of surface modified and/or functionalized ion exchange medium, a surface-modified solid phase support, an adsorption medium, a solid phase extraction medium, a resin bonded solid phase, sorbents, solid and/or porous beads, palicular and surface activated beads, mixed-bed media, filters, dual-state liquids used for immobilized liquid extraction, fibers packaged in packed columns, a surface-modified SELDI plate, a solid phase surface modified plate, surface-modified filters, solid-phase extraction cartridges and immunoassay solid phase media carriers a quantity or concentration of an isotopically tagged analyte analogue and immobilizing through adsorption or chemical attachment said isotopically tagged analyte analogue on said solid phase carrier; b) further adding to said solid phase carrier having the immobilized isotopically tagged analyte analogue from step a), a sample containing or suspected to contain an analyte of interest corresponding to said isotopically tagged analyte analogue and holding the sample on said solid phase carrier; c) conducting an equilibration step by incubating the solid phase carrier from step b) with said sample for between 1 second and 24 hours to make an equilibrated sample containing isotopically tagged analyte analogue; and d) subjecting said equilibrated sample containing said isotopically tagged analyte analogue to direct ionization and transport into a mass spectrometer for analysis.