Graphite Furnace Atomic Absorption Spectroscopy (GFAAS)
Atomic absorption is similar to the ICP in that it can determine the concentration of metals, but it has some limitations.
In GFAAS, the sample is heated electrically in a graphite tube to create a steady state of freely dissociated ground state atoms. A cathode lamp corresponding to the element of interest shines through the gaseous sample atoms on to a detector. The wavelength of the light corresponds to the amount of energy required to excite an electron from (typically) the ground to first excited state for a specific element. The detector measures the amount of the light absorbed by the atoms as they move to the excited state (the atomic absorption). Using the Beer-Lambert Law and a calibration curve, the concentration of the element of interest is calculated.
Limitation of GFAAS:
- It can only measure 48 elements vs ICP's 74 elements
- GFAAS has to measure each element individually vs ICP measuring simultaneously
- The time to run the GFAAS is longer since it must measure each element individually (including swapping out lamps)
In general, AMI prefers to use ICP over GFAAS, but we continue to have the instrumentation if there is ever a need for it.
Typical GFAAS methods include:
- ASTM E1184
- ASTM D3919
- ASTM D6357