A separation-preconcentration method utilising a mercapto-modified silica microcolumn was developed for the determination of trace amounts of Te(rv) and Te(VI) in waters by hydride generation atomic absorption spectrometry. Bottled drinking water, tap water and sea-water samples were spiked with sub-ng ml(-1) concentrations of Te(IV) and the spiked solutions were subjected to the mercapto-modified silica microcolumn separation and enrichment procedure. The spike recovery values varied between 86 and 114%. In addition to spike recovery experiments, accuracy was also verified via the analysis of a certified reference material. The limit of detection for Te(nt) in sea-water with a preconcentration factor of 50 was 0.037 ng ml(-1). The capability of the microcolumn enrichment scheme for on-line sample processing via flow manifolds was demonstrated. A detailed interference study was performed.