Speciation of chromium in waters using dispersive micro-solid phase extraction with magnetic ferrite and graphite furnace atomic absorption spectrometry.

The combination of a solid-phase microextraction process with graphite furnace atomic absorption spectrometry provides a very sensitive determination method for determining chromium in waters. Freshly prepared ferrite particles are used to retain the chromium species, and then separated by a magnet without the need for a centrifugation step. The solid phase is suspended in water and directly introduced into the graphite furnace to obtain the analytical signal. The complexation of Cr(III) with ethylenediaminetetraacetate allows the selective retention of Cr(VI), and thus the speciation of the metal. The procedure is sensitive (0.01 µg L-1 detection limit when using a 10 mL sample aliquot) and reproducible (5% relative standard deviation for five consecutive experiments at the 0.3 µg L-1 level). The reliability of the procedure is verified by analysing five certified water samples.