Principle of graphite furnace:

The primary principle of graphite furnace atomic absorption spectrophotometry (GFAAS) is essentially the similar as flame atomic absorption spectrophotometry, the just difference being in which the atomisation is achieved in a small, electrically heated graphite tube or cuvette that is heated to a temperature up to 3000°C to produce the cloud of atoms. A higher atom density and longer residence time within the electrothermal tube improve the detection limits through a factor of up to three orders of magnitude as  compared to flame AAS and we could go down to the sub-ppb range. Therefore the use of graphite cuvettes, do not sort out the issue of determining refractory elements.

It is necessary that the AAS instrument should always be calibrated through preparing at least four standard solutions over the concentration range of interest and measuring the absorbance under the same experimental conditions. The correction, if essential, should be applied to the calibration plot. Sometimes, the method of standard further is used to compensate for chemical and other interferences.

In compare to atomic absorption spectrophotometry, atomic emission spectrometry is inherently a multielement technique. Especially a high temperature of plasma ensures effectual atomisation and lead to intense atomic emission. The emission occurs from all elements at the same time and is isotropic. The simultaneous multielement determinations could be made simply through using a multichannel detection system. Multichannel devices using 2D spectral dispersion along with two dimensional arrays of detector elements offer extremely good sensitivity and low noise.