Graphite Furnace Atomic Absorption Spectrometry is a technique that is very suitable for the analysis of metals at ultra-trace levels (ng/ml). A small amount of a solution to be analysed, is injected into a graphite furnace. The furnace is heated with a special temperature-program. First the solvent of the solution is evaporated, followed by ashing of the sample, which removes most of the sample-matrix. The last stage of the heating-program is the atomisation-phase, which creates a cloud of free atoms in the graphite furnace. The concentration of free atoms in the furnace is measured by absorption of element specific irradiation through the graphite furnace. This irradiation is produced by a hollow cathode lamp, which contains the element of interest in its cathode. The amount of absorption is a measure for the concentration of the element in the sample-solution.
Some ‘volatile’ elements like arsenic, antimony and mercury can be measured as their hydrides (As, Sb,...) or as ‘cold vapour’ (Hg). With this very specific technique, the volatile hydrides are heated in a quartz tube, which again produces free atoms, that are measured with atomic absorption.