Sample contamination is one of the biggest challenges facing analytical techniques aimed at detecting ultratrace impurities in ultrapure materials. In many applications, current analytical techniques are unable to detect trace elements at sufficiently low levels, but not because of instrument limitations. These limitations arise as a result of the sample preparation process and include contamination from reagents, containers, and even the air. By eliminating sample interaction with these potential sources of contaminants and employing a new highly selective analyte preconcentration approach operating at the atomic level, PNNL is making new levels of ultratrace detection possible.

PNNL’s solid state isotope selective preconcentration technique employs implantation of one isotope of the target analyte element from the sample into a highly localized area on a clean substrate inside a plasma source mass spectrometer. A known amount of a different isotope of the same element is then co-implanted over the same localized spot, and the isotope ratio measured to determine the concentration of the analyte back to the sample. Preconcentration of the analyte is achieved by implanting the isotope atoms in a small area and by allowing the atom collection to proceed until sufficient numbers have been collected to make the actual isotope ratio measurement. By employing a laser ablation-based approach to sample and implant substrate analysis, no chemical sample preparation is required.

This new approach could be used to boost the detection limits of many types of elemental mass spectrometers including inductively coupled plasma (ICP-MS), glow discharge, and secondary ion mass spectrometers for ultrapure materials analysis.