A multicomponent quasi-equilibrium thermodynamic model of thermochemical processes in inductively coupled plasma is proposed. The electron concentrations and degrees of ionization are calculated for more than 70 elements using various modeling conditions at temperatures 6000-9000 K. A comparison is made with similar results obtained by the Saha equation for a simplified two-component plasma model. Recommendations are made on the ways of increasing the degree of ionization of elements, selecting the internal standard, using negative-ion mass spectra for analysis, and thermodynamic simulation with the use of a unified computational mode. An equation describing the sensitivity of an inductively coupled plasma mass spectrometer to the detected ion masses is proposed. With the use of experimental detection limits and calculated partial pressures of isotope ions, such well-defined sensitivity functions are obtained for industrial instruments of various types produced by various firms. This confirms the legitimacy of using the proposed multicomponent quasi-equilibrium thermodynamic model for studying the analytical characteristics of inductively coupled plasma. © 1998 MAEe cyrillic signK Hayκa/Interperiodica Publishing.