Speciation of chromium by the combination of dispersive liquid-liquid microextraction and microsample injection flame atomic absorption spectrometry

A microextraction procedure was established for the speciation of total Cr, Cr(III), and Cr(VI). Sudan blue II was used as a ligand for speciation works. Some factors affecting the recoveries of chromium species, including type of extraction and dispersive solvents, pH, ligand amount, extraction time, and matrix ions, were examined. Optimum values for the dispersive liquid-liquid microextraction method were pH 6, LOD 0.34 mu g L-1, and preconcentration factor 400. Chromium(III) was quantitatively recovered under optimal conditions, while the recovery of chromium(VI) was below 10%. The relative standard deviation for Cr(III) determinations for the 10-replicate measurement of 0.3 mu g mL(-1) Cr(III) was 6.2%. The accuracy was verified using BCR-144R Sewage Sludge, IAEA 336 Lichen, and TMDA 25.3 certified water for trace elements. The procedure was applied to speciation of chromium in water samples. Total chromium was determined in various wheat, bread, and hair samples.