Reduction of Mass Bias and Matrix Effects in Inductively Coupled Plasma Mass Spectrometry with a Supplemental Electron Source in a Negative Extraction Lens

摘要

Electrons from a heated tungsten filament are created inside the extraction lens and driven out toward the skii~xmer. These electrons move through the ion path and reduce space chaise effects between positiv~ ions in the beam. The Jon transmission efficiency is improved by factors of two (for Pb~) to 27 (for Lii. The greater sensitivity improvement for low-mass ions leads to a substantial reduction in mass bias. With the additional electrons, MO+/M+ and M~-/M~ abundance ratios in-crease but can be minimized with a small reduction in aerosol gas flow rate. No new background ions are observed with this technique. Matrix effects can be stgniflcantly diminished when the electron source is operated under the high electron current mode. The mass dependezice of matrix-induced suppression of analyte signals is essentially eliminated. Using flow injection analysis to minimize solid deppsition, the technique can tolerate Na matrix up to 10 000 ppm (1%) with only loss of analyte sensitivity.