Graphite furnace

The graphite furnace is used in atomic absorption spectroscopy (AAS). The method was developed in 1959 by Boris L'Vov and has been one of the most powerful methods for element determination in trace and ultra-trace analysis since the early 1980s . It consists of a graphite tube approx. 1.5–2 cm long and 6 mm inside diameter, which can be electrically heated. For this purpose, depending on the design, there are graphite contacts on the sides or on both ends of the tube, which the graphite tube heats up due to its electrical resistance when a voltage is applied. A protective gas atmosphere consisting of the noble gas argon prevents the pipe from burning.

With the graphite furnace AAS, dissolved samples as well as solid samples can be analyzed. Liquid samples are introduced into the graphite tube with a microdosing system. At first, the temperature is only slightly increased to evaporate the solvent . A further heating to about 1000-1200 ° C separates the matrix . The substance to be examined (the analyte ) is vaporized and atomized by very rapid heating to temperatures of up to 2800 ° C. Solid samples are placed directly in the graphite tube.

Because the entire sample is available for analysis (in contrast to the nebulizers commonly used in flame atomic absorption spectroscopy (F-AAS) and ICP-OES with their poor efficiencies) and is completely atomized in a few seconds, the detection limits are 100 - up to 1000 times lower than, for example, in the F-AAS, the typical measuring range is in the picogram to nanogram range.

The heating and cooling cycles delay the measuring cycle of the method. Sensitivity and the need for external sample preparation ( digestion ), which is usually omitted, compensate for this disadvantage.