An analytical instrument has a sample introduction system for generating a stream of particles from a sample. An ionization system atomizes and ionizes particles in the stream as they are received. The instrument has an ion pretreatment system and a mass analyzer. The ion pretreatment system is adapted to transport ions generated by the ionization system to the mass analyzer. The mass analyzer is adapted measure the amount of at least one element in individual particles from the stream by performing mass analysis on the ions from the atomized particles. The instrument can be adapted to measure the amount of many different tags, for example at least five different tags, at the same time to facilitate multi-parametric analysis of cells and other particles.