ATOMIC ABSORPTION SPECTROPHOTOMETRY (AAS)

This is a technique for elemental analysis in liquids. Metallic species can be determined in both organic and inorganic samples. It is a sensitive technique that can determine the concentration of most elements at the part - per - million (ppm) level. If lower detection limits are required then a graphite furnace is used as the excitation source (GFAAS), replacing the standard flame. GFAAS is for ultra-trace analysis. It has detection limits that exceed the conventional flame by several orders of magnitude.


Through the use of calibration curves, prepared from suitable standards, a high level of accuracy and precision (±1 to 3 %) is achieved for flame AAS. This allows for compositional as well as trace impurity analysis. Most spectral interferences and matrix effects are overcome by utilizing well characterized conditions and matrix matching of samples and standards. GFAAS has an average accuracy of ±20% (relative) which is suitable for reporting at the ultra-trace impurity level.

When using atomic absorption spectrophotometry (AAS) as an analytical
technique the absorption of light of free atoms is measured. Therefore it is one of
the branches of atomic spectroscopy, together with flame photometry (see
Standardbase techniques: “Flame Photometry” that measures the intensity of
light emitted by free atoms when their electrons return to ground state after the
excitation by light). However - unlike flame photometry - AAS is based on the
“first half” of the excitation process, while atoms absorb light getting their
electrons from the ground state to a higher energy level.