The effect of plasma density on the degree of suppression of analyte signals in ICP-MS

Possible effects of ionization phenomena on the analytical signal in inductively coupled plasma mass spectrometry with a high-temperature ion source are considered. The dependences of the degree of suppression of ion signals on the electron density are calculated and experimentally determined for ions of matrix and impurity elements. It is shown that the degree of signal suppression depends rather strongly on the electron density in the analytical zone in the presence of matrix elements with different first ionization potentials. The effects of the inductive plasma power and sputtering argon rate on the sensitivity of the mass spectrometer are studied by the example of an ICP-MS mass spectrometer (Agilent Technologies). The experimental results showed that the origin of the suppression of the analyte signals at the output is apparently associated with the ion–electron recombination of ions (both matrix and impurity ones) in the plasma region.