ATOMIC-ABSORPTION SPECTROMETRIC DETERMINATION OF MERCURY IN SOIL STANDARD REFERENCE MATERIAL FOLLOWING MICROWAVE SAMPLE PRETREATMENT

Several decomposition procedures and their influence on the determinat ion of mercury by electrothermal (ET) and cold vapour (CV) atomic abso rption spectrometry (AAS) have been studied. Soil samples were decompo sed by microwave digestion in closed and open vessels as well as by di gestion under reflux according to German standard. The use of differen t acids (HNO3, HCl or aqua regia) was evaluated and compared in respec t to their influence on the determination of mercury by ET AAS and CV AAS. The digestion solutions were analyzed by ET AAS with a palladium modifier and by CV AAS using SnCl2 or NaBH4, as reducing agents. The d etection limits obtained with different procedures were also evaluated . For the soil containing 6.25 mu g/g of Hg the ET AAS measurements we re possible. In the case of lower concentration of mercury the CV AAS determination following the microwave digestion procedure with HCl or aqua regia is recommended. The accuracy of the proposed procedure was confirmed by the determination of total mercury in SRM 2711 Montana So il.