HIGH-RESOLUTION ICP-MS - A NEW CONCEPT FOR ELEMENTAL MASS-SPECTROMETRY

Interfering molecular species are of major concern to the analyst curr ently using quadrupole based ICP-MS instrumentation. The recognized ad vantage and convenience offered ny atmospheric plasma ionisation to mu ltielement trace analysis can be significantly deteriorated by the lim ited resolving power of these analyzers. The result is poor sensitivit y 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 t o now, commercially available HR-ICP-MS systems have been derived from complex instruments originally designed to meet the requirements of o rganic mass applications. Consequently, operation and performance of t hose systems expose the compromise which had to be made between an atm ospheric plasma atomic ion source at high potential and an analyzer te chnology dedicated to molecular mass spectroscopy of organic compounds . At Finnigan MAT the first purpose designed high resolution ICP-MS ha s now been developed, which can be operated in high and low resolution mode at enhanced sensitivity. An innovative electric and magnetic fie ld 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 resoluti on. By extremely rapid peak switching, for example, all barium isotope s can be monitored in less than 100 ms with more than 90% on-peak dete ction 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.