ISOTOPIC COMPOSITION OF COPPER IN SERUM BY INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRY

The accurate, direct measurement of the 63Cu: 65Cu ratio in blood plasma or serum by inductively coupled plasma mass spectrometry is precluded by the existence of the polyatomic species ArNa+ and possibly PO2+ at mass 63. Copper in serum or plasma is largely bound to the proteins caeruloplasmin, albumin and transcuprein. Only very small amounts of copper are present in low molecular mass forms. Size-exclusion chromatography can be used to separate copper in serum from interfering sodium and phosphate ions. An accurate measurement of the 63Cu:65Cu ratio can be made directly on the desalted protein solution.