ISO 17211:2015 describes the method for the sampling and determination of selenium compounds in both vapour phase and solid phase that are entrained in flue gases carried in stacks or ducts. The selenium content in flue gas is expressed as a mass concentration of elemental selenium in the stack gas. Particulate and gaseous selenium compounds are captured by a filter and an absorber solution, respectively. The total concentration of selenium compounds in flue gas is expressed as the sum of both concentrations. The concentrations of selenium in both samples are determined using inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS) or graphite furnace atomic absorption spectrometry (GFAAS). Hydride generation (HG) techniques coupled to atomic spectrometry can also be used such as HG-AAS, HG-AFS (atomic fluorescence spectrometry), HG-ICP-OES and HG-ICP-MS. The detection limit for gaseous selenium compounds is 0,3 μg/m3 using HG-ICP-MS at a sampling volume of 0,12 m3. The detection limit for particulate selenium compounds is 0,001 2 μg/m3 using this technique at a sampling volume of 2,0 m3.