Method of measurement in biological systems

A method of quantifying risks from exposure to chemicals which comprises:

• a. administering doses of a xenobiotic substance labeled with a long-lived radioisotope to selected animal hosts at a plurality of dose levels,
• b. harvesting selected tissues from said hosts at selected time points after administration of said doses,
• c. extracting DNA from said tissues to remove unbound radioisotope therefrom,
• d. converting said DNA to a material which efficiently produces charged ions in an ion source without introducing significant isotopic fractionation, and
• e. measuring the radioisotope concentration of the radioisotope in said material using an accelerator mass spectrometer.

A method for measuring exposure to chemicals under therapeutic regimes which comprises:

• a. administering a chemical to selected animal hosts at a plurality of dose levels, wherein the chemical is labeled with a long-lived radioisotope, and the doses are sufficiently low to avoid significant damage to the hosts,
• b. harvesting selected tissues or fluid from said hosts at selected time points after administration of said doses,
• c. extracting DNA from said tissues to remove unbound radioisotopes therefrom,
• d. converting said DNA to a material which efficiently produces charged ions in an ion source without introduction of significant isotopic fractionation, and
• e. measuring the radioisotope concentration of the radioisotope in said material using an accelerator mass spectrometer.