| time-of-flight mass spectrometer (TOFMS) has been designed, developed, and evaluated as a mass analyzer interfaced to plasma ion sources for use in routine multielement analysis. The important performance features of the TOFMS are: (1) simultaneous extraction of ion packets representative of the ion source, (2) mass spectrometer repetition rates between 10 and 20 kHz, and (3) resolving powers ranging from 1500-2000 (fwhm). The orthogonal mass spectrometer geometry is suited to sampling of continuous ion sources with high ion-beam intensities. This attribute allowed the analysis of liquid samples with an inductively coupled plasma (ICP) and direct analysis of solid samples with a glow discharge (GD). A mass spectrometer interface was developed to allow the easy interchange between ICP and GD ion sources with no other instrumental changes. Much of the instrumental development was aimed at characterizing and improving the performance of the ICP-TOFMS combination. The ICP-TOFMS detection limits for elements studied ranged from 10-1000 parts-per-trillion in solution with a linear dynamic range of 4-5 orders of magnitude. Current detection limits are limited primarily by the density of the continuous ion beam focused into the TOFMS extraction region. Instrumental precision was between 5-10% relative standard deviation (RSD), and, with the use of internal standardization, precision improvements to 1-2% RSD levels were demonstrated. The simultaneous extraction employed in the TOFMS should ultimately improve the obtainable precision for isotope-ratio measurements to... |
