Use of high surface area TiO$_2$ for preconcentration and following determination of Cr species by on-line flow injection inductively coupled plasma atomic emission spectrometry

A flow-injection analysis (FIA) system incorporating two microcolumns of TiO 2 was used for the developing of an on- line method for preconcentration and sequential determination of Cr 3+ and Cr6+ species by inductively coupled plasma atomic emission spectrometry (ICP-AES). The optimal conditions for both analytes have been obtained. With a sample volume of 10-50 ml and an elution volume of 500 µl, a signal was 20-100 times higher than the signal given by a continuous aspiration system. The method gave good reproducibility with precisions less than 7 % RSD for 5 replicates at the 10 ng/ml level for both Cr- species. Recoveries between 95 and 98 % were obtained for Cr 3+ and Cr6+. The preconcentration system and the methodology proposed were validated on several natural water samples, on reference water samples as well as on synthetic seawater. It was found that the on-line detection using ICP-AES allows sequential Cr speciation analysis at the low concentration levels (ng/l) usually encountered in these media.