One of the most common activities of chemists is to determine the identity of elements and compounds present in a sample of material. If a chemist wishes to analyze a sample to find what elements or compounds are present, that is, to identify the elements and compounds present, she or he will choose a qualitative analysis method. Once the species that are present in a sample is known, the analytical chemist may choose to determine how much of each species is present using a quantitative analytical method. Some methods perform both qualitative and quantitative results, but most are used for one purpose or the other.

Literally hundreds of techniques for determining the identity of elements and compounds are available to chemists. The decision on which technique to use depends on many factors, including the physical state of the sample, the...