The sensitivity of detection of ions as a function of the atomic ion mass, the ionization potential of the elements, and the dissociation energy of the corresponding monoxides is studied by inductively coupled plasma mass spectrometry in a "cold" plasma regime (T = 2500-3000 K). The ionization potential and the atomic mass of the matrix elements are main factors that determine matrix ionization effects which show up at concentrations higher than 10-6 M. The "cold" plasma technique can be used for highly sensitive determination of K, Ca, Fe, and other elements with ionization potentials less than 8 cV only in solutions with low salt concentration.