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

Abstract

The adsorption of Cr³⁺ and Cr⁶⁺ on different metal oxides (MgO, Al₂O₃, TiO₂, ZrO₂ and CeO₂) with high specific surface areas was studied under different conditions. It was established that SiO₂ can be used for selective and quantitative adsorption of Cr³⁺, whereas, depending on the pH, TiO₂ and Al₂O₃ 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 high surface area TiO₂ (anatase) was developed. The conditions for quantitative and reproducible preconcentration, elution and subsequent ETAAS determination were established. The retention efficiency is better than 95% for Cr³⁺ and Cr⁶⁺, giving a sensitivity enhancement of 100 for a 100 ml sample volume. The proposed method is characterized by high precision and high reproducibility. The detection limit based on the 3ς criterion is 30 ng l⁻¹ for Cr³⁺ and 24 ng l⁻¹ for Cr⁶⁺.