Techniques for chemical analysis of both inorganic and organic solids in the mass spectrometer are now well established. A new instrument in which impurities in inorganic solids can be detected at a concentration of 0.001 ppm (atomic) is described and analyses of a variety of materials are presented. A high resolution instrument now being built for the investigation of complex organic compounds will permit identification of ions by means of mass measurement to a few parts in 10,000,000. Chemical analysis by the isotope dilution method is also discussed.