In the present paper, lithium was determined in river sediment using slurry sampling and electrothermal atomic absorption spectrometry (ET AAS) after L'vov platform coating with zirconium (as a permanent chemical modifier). The performance of this modifier and its distribution on the L'vov platform after different heating cycles were evaluated using synchrotron radiation X-ray fluorescence (SRXRF) and imaging scanning electron microscopy (SEM) techniques. The analytical conditions for lithium determination in river sediment slurries were also investigated and the best conditions were obtained employing 1300 and 2300degreesC for pyrolysis and atomization temperatures, respectively. In addition, 100 mg of sediment samples were prepared using 4.0 mol l(-1) HNO3. The Zr-coating permitted lithium determination with good precision and accuracy after 480 heating cycles using the same platform for slurry samples. The sediment samples were collected from five different points of the Cachoeira river, S (a) over tildeo Paulo, Brazil. The detection and quantification limits were, respectively, 0.07 and 0.23 mug l(-1). (C) 2003 Elsevier B.V. All rights reserved.623619626