Atomic absorption spectroscopy analyzes samples by generating gaseous atoms from a liquid sample and measuring their absorption of light from a hollow cathode lamp. There are two main methods: flame atomic absorption uses a flame to generate atoms, while electrothermal atomic absorption uses a graphite furnace. Both work by applying Beer's law to relate absorption to concentration. The instrument isolates a spectral line, alternates the light with a chopper, and uses a detector to measure absorption and calculate concentrations. Interferences can occur from compound formation or ionization, but various cures exist such as using different temperatures, flames, or additives.