Lead Analysis by Graphite Furnace Atomic Absorption (GFAA)

When using the furnace technique in conjunction with an atomic absorption spectrophotometer, a representative aliquot of a sample is placed in the graphite tube in the furnace, evaporated to dryness, charred, and atomized. 

A greater percentage of available analyte atoms is vaporized and dissociated for absorption in the GFAA tube when compared to the flame therefor the use of smaller sample volumes or detection of lower concentrations of elements are possible. The principle is essentially the same as with direct aspiration atomic absorption (FLAA), except that a furnace, rather than a flame, is used to atomize the sample. Radiation from a given excited element is passed through the vapor containing ground-state atoms of that element. The intensity of the transmitted radiation decreases in proportion to the amount of the ground-state element in the vapor. The metal atoms to be measured are placed in the beam of radiation by increasing the temperature of the furnace, thereby causing the injected specimen to be volatilized. A monochromator isolates the characteristic radiation from the hollow cathode lamp, and a photosensitive device measures the attenuated transmitted radiation. Furnace devices are a most useful means of extending detection limits to lower levels.