With the rise in general awareness of the effects of trace chemicals in the environment on man's health, it has been realized that traditional methods of analysis are often inadequate. Reliable analyses are needed in the fractional parts-per- million range of contaminants in condensed phases, and of the order of micrograms per cubic meter in air. Trying to get meaningful answers regarding such minute amounts raises cogent problems in all stages of an analysis. It is most appropriate, therefore, that the 1971 Eastern Analytical Symposium should have four half-day sessions devoted to this...