Publisher Summary “Trace analysis” indicates the separation and detection of a minor component in a sample, where its concentration is less than about 100 parts per million (ppm). Types of sample analysis that are included in this category are the detection of: (1) impurities in technical materials, (2) airborne pollutants, (3) trace components in bulk water, (4) minor components in bulk solids, for example, pesticide residues in crops and foodstuffs, and (5) drugs and their metabolites in body fluids. Concentration of solids from the atmosphere is accomplished by aspirating quantities of air through low-porosity filters; the volume of gas sampled is monitored using a “gas meter” capable of recording volume corrected for pressure and temperature variations. Prior to analysis by most techniques, the most effective method of concentrating dissolved solids from water is by the method of freeze drying. The method enables comparatively large volumes of water to be reduced to low bulk or dryness with minimal loss of solids that are present in the water.