Analytical chemist using an atomic absorption (AA) spectrometer to determine the concentration of a metal (unknown) in a liquid sample. The technique involves converting sample (seen in aqueous solution in beaker) into an atomic vapour and measuring the absorbance of the vapour at a selected wavelength; this is characteristic for each individual element. The liquid sample is converted into an atomic vapour by spraying it into an air-acetylene flame (the liquid is sucked through the aspirator tube into yellow flame). For this reason AA spectrometry is also known as absorption flame photometry. The technique is applicable to determination of some 40 metals.