A system and method for analysis of minute quantities of contaminants in water. Liquid water is converted to water vapor and then excited into a plasma state with microwave radiation. Optical emissions from the plasma are spectrally analyzed to provide qualitative and/or quantitative analyses of the contaminants in the water. Preferred embodiments provide special techniques for generating the water vapor from a water stream; exciting the water vapor to a plasma state; varying and controlling the plasma energy; introducing samples into an existing plasma; collecting emissions from the plasma from a variety of angles; selecting the optical collection angles; protecting the analysis optics from the plasma; exhausting the spent plasma gases back into the water stream; and analyzing the results to yield concentrations of elements and molecules in the sample.