Under the conditions of the method specified (thermal decomposition of selenium hydride for AAS), only Se(IV) is quantitatively converted to the hydride. To avoid errors in determination, other oxidation states need to be converted to Se(IV) prior to the determination. The absorbance is measured at a wavelength of 196,0 nm. The method determines selenium and organically bonded selenium in drinking waters, ground waters and surface waters, in a concentration range of 1 µg/l and 10 µg/l. Higher concentrations can be determined by a suitable dilution of the water sample.