Since standard reference materials for soils and related samples, especially ones with a certified thallium content, are hard to obtain. the accuracy of methods for trace pollutant determination in such materials is often checked by comparison with the results obtained by independent methods. Conventional flame atomic absorption spec trometry (AAS) is still widely used despite devel opments with electrothermal AAS. There are less matrix interferences and related systematic errors with the flame technique. The major limitation of