The chemist is responsible for the analysis of priority pollutant trace metals by a specialized technique called atomic absorption (AA). Priority pollutant metals include antimony, arsenic, beryllium, cadmium, chromium, copper, mercury, molybdenum, nickel, lead, selenium, silver, thallium, and zinc. A small volume of sample is super heated to a temperature that breaks the sample into atoms. The atomized sample is then irradiated by a lamp. Each metal absorbs light energy at a specific wavelength of the electromagnetic spectrum. A detector measures this absorbance, which is correlated to concentration through the use of standards of known concentration. Trace metals are detected at concentration levels of parts per billion (ppb), that is, for every 1,000,000,000 atoms, one metal atom can be detected!
The graphite furnace instrument (GFAA) uses a small graphite tube that is heated to 2200 degrees Celsius to atomize the sample. The fast sequential instrument (FSAA) uses a flame to atomize the sample rapidly, though it is not as sensitive as the GFAA.