High resolution ICP-MS — a new concept for elemental mass spectrometry

Interfering molecular species are of major concern to the analyst currently using quadrupole based ICP-MS instrumentation. The recognized advantage and convenience offered by atmospheric plasma ionisation to multielement trace analysis can be significantly deteriorated by the limited resolving power of these analyzers. The result is poor sensitivity and lack of selectivity. With respect to sensitivity and resolution significant enhancement can be achieved by using magnetic sector based high resolution analyzers instead of quadrupoles. Unfortunately, up to now, commercially available HR-ICP-MS systems have been derived from complex instruments originally designed to meet the requirements of organic mass applications. Consequently, operation and performance of those systems expose the compromise which had to be made between an atmospheric plasma atomic ion source at high potential and an analyzer technology dedicated to molecular mass spectroscopy of organic compounds. At Finnigan MAT the first purpose designed high resolution ICP-MS has now been developed, which can be operated in high and low resolution mode at enhanced sensitivity. An innovative electric and magnetic field scanning strategy (SynchroScan) results in high on-peak duty cycles. Improved magnet technology offers high speed quadrupole style survey scans covering the full elemental mass range at nominal mass resolution. By extremely rapid peak switching, for example, all barium isotopes can be monitored in less than 100 ms with more than 90% on-peak detection efficiency. Examples are shown for computer controlled high and low resolution scan modes demonstrating the analytical performance of the new instrument concept. A comparison of detection limits achieved in low and high resolution mode is given.