Live HeLa cells immobilized on Sephadex G-50 beads were used as a medium for the preconcentration and speciation of inorganic arsenic. The sorption of arsenic species by live HeLa cells involves both surface uptake and bioaccumulation within the cells. At pH 3.0, the cells accumulate arsenate with high specificity over arsenite: 83.0 +/- 1.3% of the arsenate was sorbed while the retention of arsenite was negligible at 2.1 +/- 0.6%. The speciation of inorganic arsenic could thus be performed by direct determination of arsenate followed by quantifying total inorganic arsenic after conversion of arsenite to arsenate. We formed a disposable live cell preconcentration microcolumn with the live HeLa cells immobilized on Sephadex G-50 beads. After the sample was passed through the column for sorption to occur, the cells and any retained arsenate were stripped with 2 M HNO(3). The arsenic in the 30 microL eluate was directly measured by graphite furnace atomic absorption spectrometry. A new microcolumn was used for each sample. With a sample volume of 450 muL, a S/N = 3 limit of detection (LOD) of 0.05 microg/L and a linear range of 0.15-2.5 microg/L were attained; the relative standard deviation (RSD) was 1.7% at 1.25 microg/L. The procedure was validated by arsenic speciation in certified reference river water.