DIN ISO 20279:2006-01

Thallium is extracted from soil by a mixture of nitric acid and hydrogen peroxide, and determined in solution by electrothermal atomic absorption spectrometry, in which discrete volumes of sample solution are dispensed into a graphite tube. By increasing the temperature of this tube stepwise, the processes of drying, thermal decomposition of the matrix and thermal dissociation into free atoms occur. The resulting absorption signal should (under optimum conditions) be a sharp symmetrical peak with a height proportional to the element concentration in solution.