Chromium speciation analysis by solid-phase extraction on a high surface area TiO2

The adsorption of Cr3+ and Cr6+ On different metal oxides (MgO, Al2O3, TiO2 , ZrO2 and CeO2) with high specific surface areas was studied under differe nt conditions. It was established that SiO2 can be used for selective and q uantitative adsorption of Cr3+, whereas, depending on the pH, TiO2 and Al2O 3 can selectively adsorb Cr3+ Or Cr6+. On the basis of the results obtained , a simple and sensitive method for the selective determination of Cr3+ and Cr6+ in natural water samples using a column solid-phase extraction on a h igh surface area TiO2 (anatase) was developed. The conditions for quantitat ive and reproducible preconcentration, elution and subsequent ETAAS determi nation were established. The retention efficiency is better than 95% for Cr (3+ an)d Cr6+, giving a sensitivity enhancement of 100 for a 100 ml sample volume. The proposed method is characterized by high precision and high rep roducibility. The detection limit based on the 3 sigma criterion is 30 ng 1 (-1) for Cr3+ and 24 ng 1(-1) for Cr6+.