Patent ID: 7985589

Claim:
A calibrating method for use determining the quantity of an analyte labeled with an accelerator mass spectrometry isotope in a test sample, said calibrating method comprising: (i) contacting a plurality of samples contaminated with neither said analyte nor a non-labeled counterpart analyte with a known quantity of said counterpart analyte and a quantity C of said analyte to afford a plurality of calibrating samples, wherein each of said calibrating samples contains a known quantity of said counterpart analyte and a different quantity C of said analyte; (ii) measuring by accelerator mass spectrometry the quantity C of said analyte added to each of the plurality of samples; (iii) separating said analyte and said counterpart analyte from other species in the plurality of samples to afford a plurality of purified samples; (iv) measuring a quantity A of said analyte in said purified samples by accelerator mass spectrometry; and (v) measuring a quantity B of said counterpart analyte in said purified samples; and relating the measured quantities C to ratios of measured quantities A and B for each of the plurality of samples to allow for determination of the quantity of said analyte in said test sample.