Isotope ratio analysis

Measurement of relative abundances of two or more isotopes of an element to 0.01 to 0.5 percent precision. Lead ratios fingerprint the ore deposit a bullet was cast from, 87Sr/86Sr traces geographic origin, and 235U/238U anchors nuclear forensic attribution. Quadrupole ICP-MS reaches roughly 0.1 percent precision; multicollector sector instruments at BARC reach a few parts per million.