FAAS (Flame Atomic Absorption Spectroscopy)
FAAS is used for the ppm to high ppb determination of metals in aqueous solutions (typically stabilized with mineral acids)
An aquous sample is aspirated into a flame that has a beam of light passing through it which is specific to the element being determined. Atoms of that element absorb some of the light, which is measued by a detector. The absorbance is proportional to the concentration of the analyte in the origional sample. Thus, by comparing the absorbance in an unknown sample with that of solutions of known composition (standards), we can determine the concentration of the analyte in the origional sample.